@article {49143, title = {Juvenile hormone reveals mosaic developmental programs in the metamorphosing optic lobe of Drosophila melanogaster.}, journal = {Biology Open}, year = {2018}, month = {2018 Apr 04}, abstract = {

The development of the adult optic lobe (OL) of is directed by a wave of ingrowth of the photoreceptors over a two day period at the outset of metamorphosis which is accompanied by the appearance of the pupal-specific transcription factor Broad-Z3 (Br-Z3) and expression of early drivers in OL neurons. During this time, there are pulses of ecdysteroids that time the metamorphic events. At the outset, the transient appearance of juvenile hormone (JH) prevents precocious development of the OL caused by the ecdysteroid peak that initiates pupariation, but the artificial maintenance of JH after this time misdirects subsequent development. Axon ingrowth, Br-Z3 appearance and the expression of early drivers were unaffected, but aspects of later development such as the dendritic expansion of the lamina monopolar neurons and the expression of late drivers were suppressed. This effect of the exogenous JH mimic (JHM) pyriproxifen is lost by 24 hr after pupariation. Part of this effect of JHM is due to its suppression of the appearance of ecdysone receptor EcR-B1 that occurs after pupation and during early adult development.

}, issn = {2046-6390}, doi = {10.1242/bio.034025}, author = {Riddiford, Lynn M and Truman, James W and Nern, Aljoscha} } @article {48478, title = {Genetic tools to study juvenile hormone action in Drosophila.}, journal = {Scientific Reports}, volume = {7}, year = {2017}, month = {2017 May 18}, pages = {2132}, abstract = {

The insect juvenile hormone receptor is a basic helix-loop-helix (bHLH), Per-Arnt-Sim (PAS) domain protein, a novel type of hormone receptor. In higher flies like\ Drosophila, the ancestral receptor\ germ cell-expressed\ (gce) gene has duplicated to yield the paralog\ Methoprene-tolerant\ (Met). These paralogous receptors share redundant function during development but play unique roles in adults. Some aspects of JH function apparently require one receptor or the other. To provide a foundation for studying JH receptor function, we have recapitulated endogenous JH receptor expression with single cell resolution. Using Bacteria Artificial Chromosome (BAC) recombineering and a transgenic knock-in, we have generated a spatiotemporal expressional atlas of\ Metand\ gce\ throughout development. We demonstrate JH receptor expression in known JH target tissues, in which temporal expression corresponds with periods of hormone sensitivity. Larval expression largely supports the notion of functional redundancy. Furthermore, we provide the neuroanatomical distribution of JH receptors in both the larval and adult central nervous system, which will serve as a platform for future studies regarding JH action on insect behavior.

}, doi = {10.1038/s41598-017-02264-4}, author = {Baumann, Aaron A and Texada, Michael J and Chen, Hui-Min and Etheredge, Jack N and Miller, D L and Picard, Serge and Warner, Raechel D and Truman, James W and Riddiford, Lynn M} } @article {6883, title = {The developmental control of size in insects.}, journal = {Wiley Interdisciplinary Reviews: Developmental Biology}, volume = {3}, year = {2014}, month = {2014 Jan/Feb}, pages = {113-34}, abstract = {

The mechanisms that control the sizes of a body and its many parts remain among the great puzzles in developmental biology. Why do animals grow to a species-specific body size, and how is the relative growth of their body parts controlled to so they grow to the right size, and in the correct proportion with body size, giving an animal its species-characteristic shape? Control of size must involve mechanisms that somehow assess some aspect of size and are upstream of mechanisms that regulate growth. These mechanisms are now beginning to be understood in the insects, in particular in Manduca sexta and Drosophila melanogaster. The control of size requires control of the rate of growth and control of the cessation of growth. Growth is controlled by genetic and environmental factors. Insulin and ecdysone, their receptors, and intracellular signaling pathways are the principal genetic regulators of growth. The secretion of these growth hormones, in turn, is controlled by complex interactions of other endocrine and molecular mechanisms, by environmental factors such as nutrition, and by the physiological mechanisms that sense body size. Although the general mechanisms of growth regulation appear to be widely shared, the mechanisms that regulate final size can be quite diverse. WIREs Dev Biol 2014, 3:113{\textendash}134. doi: 10.1002/wdev.124

}, issn = {1759-7684}, doi = {10.1002/wdev.124}, author = {Nijhout, H. Frederik and Riddiford, Lynn M and Mirth, Christen and Shingleton, Alexander W and Suzuki, Yuichiro and Callier, Viviane} } @article {6961, title = {Reproductive status, endocrine physiology and chemical signaling in the Neotropical, swarm-founding eusocial wasp, Polybia micans Ducke (Vespidae: Epiponini).}, journal = {The Journal of Experimental Biology}, volume = {217}, year = {2014}, month = {2014 Apr 17}, pages = {2399-410}, abstract = {

In the evolution of caste-based societies in Hymenoptera, the classical insect hormones, juvenile hormone (JH) and ecdysteroids, were co-opted into new functions. Social wasps, which show all levels of sociality and lifestyles, are an ideal group to study such functional changes. Virtually all studies on the physiological mechanisms underlying reproductive division of labor and caste functions in wasps have been done on independent-founding paper wasps, and the majority of these studies have focused on species specially adapted for overwintering. The relatively little studied tropical swarming-founding wasps of the Epiponini (Vespidae) are a diverse group of permanently social wasps, with some species maintaining caste flexibility well into the adult phase. We investigated the behavior, reproductive status, JH and ecdysteroid titers in hemolymph, ecdysteroid content of the ovary and cuticular hydrocarbon (CHC) profiles in the caste-monomorphic, epiponine wasp Polybia micans Ducke. We found that the JH titer was not elevated in competing queens from established multiple-queen nests, but increased in lone queens that lack direct competition. In queenless colonies, JH titers rose transiently in young potential reproductives upon challenge by nestmates, suggesting that JH may prime the ovaries for further development. Ovarian ecdysteroids were very low in workers but higher and correlated with the number of vitellogenic oocytes in the queens. Hemolymph ecdysteroid levels were low and variable in both. Profiles of P. micans CHCs reflected caste, age and reproductive status, but were not tightly linked to either hormone. These findings show a significant divergence in hormone function in swarm-founding wasps compared to independent-founding ones.

}, issn = {1477-9145}, doi = {10.1242/jeb.096750}, author = {Kelstrup, Hans C and Hartfelder, Klaus and Nascimento, Fabio S and Riddiford, Lynn M} } @article {45785, title = {The role of juvenile hormone in dominance behavior, reproduction and cuticular pheromone signaling in the caste-flexible epiponine wasp, Synoeca surinama.}, journal = {Frontiers in Zoology}, volume = {11}, year = {2014}, month = {2014}, pages = {78}, abstract = {

BACKGROUND: The popular view on insect sociality is that of a harmonious division of labor among two morphologically distinct and functionally non-overlapping castes. But this is a highly derived state and not a prerequisite for a functional society. Rather, caste-flexibility is a central feature in many eusocial wasps, where adult females have the potential to become queens or workers, depending on the social environment. In non-swarming paper wasps (e.g., Polistes), prospective queens fight one another to assert their dominance, with losers becoming workers if they remain on the nest. This aggression is fueled by juvenile hormone (JH) and ecdysteroids, major factors involved in caste differentiation in most eusocial insects. We tested whether these hormones have conserved aggression-promoting functions in Synoeca surinama, a caste-flexible swarm-founding wasp (Epiponini) where reproductive competition is high and aggressive displays are common.

RESULTS: We observed the behavioral interactions of S. surinama females in field nests before and after we had removed the egg-laying queen(s). We measured the ovarian reproductive status, hemolymph JH and ecdysteroid titers, ovarian ecdysteroid content, and analyzed the cuticular hydrocarbon (CHC) composition of females engaged in competitive interactions in both queenright and queenless contexts. These data, in combination with hormone manipulation experiments, revealed that neither JH nor ecdysteroids are necessary for the expression of dominance behaviors in S. surinama. Instead, we show that JH likely functions as a gonadotropin and directly modifies the cuticular hydrocarbon blend of young workers to match that of a reproductive. Hemolymph ecdysteroids, in contrast, are not different between queens and workers despite great differences in ovarian ecdysteroid content.

CONCLUSIONS: The endocrine profile of S. surinama shows surprising differences from those of other caste-flexible wasps, although a rise in JH titers in replacement queens is a common theme. Extensive remodeling of hormone functions is also evident in the highly eusocial bees, which has been attributed to the evolution of morphologically defined castes. Our results show that hormones which regulate caste-plasticity can lose these roles even while caste-plasticity is preserved.

}, issn = {1742-9994}, doi = {10.1186/s12983-014-0078-5}, author = {Kelstrup, Hans C and Hartfelder, Klaus and Nascimento, Fabio S and Riddiford, Lynn M} } @article {5635, title = {The juvenile hormone signaling pathway in insect development.}, journal = {Annual Review of Entomology}, volume = {58}, year = {2013}, month = {2013 Jan 7}, pages = {181-204}, abstract = {

The molecular action of juvenile hormone (JH), a regulator of vital importance to insects, was until recently regarded as a mystery. The past few years have seen an explosion of studies of JH signaling, sparked by a finding that a JH-resistance gene, Methoprene-tolerant (Met), plays a critical role in insect metamorphosis. Here, we summarize the recently acquired knowledge on the capacity of Met to bind JH, which has been mapped to a particular ligand-binding domain, thus establishing this bHLH-PAS protein as a novel type of an intracellular hormone receptor. Next, we consider the significance of JH-dependent interactions of Met with other transcription factors and signaling pathways. We examine the regulation and biological roles of genes acting downstream of JH and Met in insect metamorphosis. Finally, we discuss the current gaps in our understanding of JH action and outline directions for future research.

}, issn = {1545-4487}, doi = {10.1146/annurev-ento-120811-153700}, author = {Jindra, Marek and Palli, Subba R and Riddiford, Lynn M} } @article {6271, title = {Microarrays reveal discrete phases in juvenile hormone regulation of mosquito reproduction.}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {110}, year = {2013}, month = {2013 Jun 11}, pages = {9623-4}, keywords = {Aedes, Animals, Female, Gene Expression Profiling, Juvenile Hormones, Methoprene}, issn = {1091-6490}, doi = {10.1073/pnas.1307487110}, author = {Riddiford, Lynn M} } @article {6383, title = {A molt timer is involved in the metamorphic molt in Manduca sexta larvae.}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {110}, year = {2013}, month = {2013 Jul 30}, pages = {12518-25}, abstract = {

Manduca sexta larvae are a model for growth control in insects, particularly for the demonstration of critical weight, a threshold weight that the larva must surpass before it can enter metamorphosis on a normal schedule, and the inhibitory action of juvenile hormone on this checkpoint. We examined the effects of nutrition on allatectomized (CAX) larvae that lack juvenile hormone to impose the critical weight checkpoint. Normal larvae respond to prolonged starvation at the start of the last larval stage, by extending their subsequent feeding period to ensure that they begin metamorphosis above critical weight. CAX larvae, by contrast, show no homeostatic adjustment to starvation but start metamorphosis 4 d after feeding onset, regardless of larval size or the state of development of their imaginal discs. By feeding starved CAX larvae for various durations, we found that feeding for only 12-24 h was sufficient to result in metamorphosis on day 4, regardless of further feeding or body size. Manipulation of diet composition showed that protein was the critical macronutrient to initiate this timing. This constant period between the start of feeding and the onset of metamorphosis suggests that larvae possess a molt timer that establishes a minimal time to metamorphosis. Ligation experiments indicate that a portion of the timing may occur in the prothoracic glands. This positive system that promotes molting and the negative control via the critical weight checkpoint provide antagonistic pathways that evolution can modify to adapt growth to the ecological needs of different insects.

}, issn = {1091-6490}, doi = {10.1073/pnas.1311405110}, author = {Suzuki, Yuichiro and Koyama, Takashi and Hiruma, Kiyoshi and Riddiford, Lynn M and Truman, James W} } @article {6654, title = {Regulation of onset of female mating and sex pheromone production by juvenile hormone in Drosophila melanogaster.}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {110}, year = {2013}, month = {2013 Nov 5}, pages = {18321-6}, abstract = {Juvenile hormone (JH) coordinates timing of female reproductive maturation in most insects. In Drosophila melanogaster, JH plays roles in both mating and egg maturation. However, very little is known about the molecular pathways associated with mating. Our behavioral analysis of females genetically lacking the corpora allata, the glands that produce JH, showed that they were courted less by males and mated later than control females. Application of the JH mimic, methoprene, to the allatectomized females just after eclosion rescued both the male courtship and the mating delay. Our studies of the null mutants of the JH receptors, Methoprene tolerant (Met) and germ cell-expressed (gce), showed that lack of Met in Met(27) females delayed the onset of mating, whereas lack of Gce had little effect. The Met(27) females were shown to be more attractive but less behaviorally receptive to copulation attempts. The behavioral but not the attractiveness phenotype was rescued by the Met genomic transgene. Analysis of the female cuticular hydrocarbon profiles showed that corpora allata ablation caused a delay in production of the major female-specific sex pheromones (the 7,11-C27 and -C29 dienes) and a change in the cuticular hydrocarbon blend. In the Met(27) null mutant, by 48 h, the major C27 diene was greatly increased relative to wild type. In contrast, the gce(2.5k) null mutant females were courted similarly to control females despite changes in certain cuticular hydrocarbons. Our findings indicate that JH acts primarily via Met to modulate the timing of onset of female sex pheromone production and mating.}, issn = {1091-6490}, doi = {10.1073/pnas.1318119110}, author = {Bilen, Julide and Atallah, Jade and Azanchi, Reza and Levine, Joel D and Riddiford, Lynn M} } @article {5626, title = {How does juvenile hormone control insect metamorphosis and reproduction?}, journal = {General and Comparative Endocrinology}, volume = {179}, year = {2012}, month = {2012 Dec 1}, pages = {477-84}, abstract = {

In insects juvenile hormone (JH) regulates both metamorphosis and reproduction. This lecture focuses on our current understanding of JH action at the molecular level in both of these processes based primarily on studies in the tobacco hornworm Manduca sexta, the flour beetle Tribolium castaneum, the mosquito Aedes aegypti, and the fruit fly Drosophila melanogaster. The roles of the JH receptor complex and the transcription factors that it regulates during larval molting and metamorphosis are summarized. Also highlighted are the intriguing interactions of the JH and insulin signaling pathways in both imaginal disc development and vitellogenesis. Critical actions of JH and its receptor in the timing of maturation of the adult optic lobe and of female receptivity in Drosophila are also discussed.

}, issn = {1095-6840}, doi = {10.1016/j.ygcen.2012.06.001}, author = {Riddiford, Lynn M} } @article {3919, title = {When is weight critical?}, journal = {The Journal of Experimental Biology}, volume = {214}, year = {2011}, month = {2011 May 15}, pages = {1613-5}, keywords = {20th Century, Animals, Biological, Body Size, Ecdysone, History, Juvenile Hormones, Manduca, Metamorphosis, Pupa}, issn = {1477-9145}, doi = {10.1242/jeb.049098}, author = {Riddiford, Lynn M} } @article {2493, title = {Developmental expression of mRNAs for epidermal and fat body proteins and hormonally regulated transcription factors in the tobacco hornworm, Manduca sexta.}, journal = {Journal of Insect Physiology}, volume = {56}, year = {2010}, month = {2010 Oct}, pages = {1390-5}, abstract = {

This paper provides a compilation of diagrammatic representations of the expression profiles of epidermal and fat body mRNAs during the last two larval instars and metamorphosis of the tobacco hornworm, Manduca sexta. Included are those encoding insecticyanin, three larval cuticular proteins, dopa decarboxylase, moling, and the juvenile hormone-binding protein JP29 produced by the dorsal abdominal epidermis, and arylphorin and the methionine-rich storage proteins made by the fat body. The mRNA profiles of the ecdysteroid-regulated cascade of transcription factors in the epidermis during the larval molt and the onset of metamorphosis and in the pupal wing during the onset of adult development are also shown. These profiles are accompanied by a brief summary of the current knowledge about the regulation of these mRNAs by ecdysteroids and juvenile hormone based on experimental manipulations, both in vivo and in vitro.

}, keywords = {Animals, Developmental, Epidermis, Fat Body, Gene Expression Regulation, Insect Hormones, Insect Proteins, Manduca, Messenger, RNA, Transcription Factors}, issn = {1879-1611}, doi = {10.1016/j.jinsphys.2010.03.029}, author = {Hiruma, Kiyoshi and Riddiford, Lynn M} } @article {2494, title = {A role for juvenile hormone in the prepupal development of Drosophila melanogaster.}, journal = {Development}, volume = {137}, year = {2010}, month = {2010 Apr}, pages = {1117-26}, abstract = {

To elucidate the role of juvenile hormone (JH) in metamorphosis of Drosophila melanogaster, the corpora allata cells, which produce JH, were killed using the cell death gene grim. These allatectomized (CAX) larvae were smaller at pupariation and died at head eversion. They showed premature ecdysone receptor B1 (EcR-B1) in the photoreceptors and in the optic lobe, downregulation of proliferation in the optic lobe, and separation of R7 from R8 in the medulla during the prepupal period. All of these effects of allatectomy were reversed by feeding third instar larvae on a diet containing the JH mimic (JHM) pyriproxifen or by application of JH III or JHM at the onset of wandering. Eye and optic lobe development in the Methoprene-tolerant (Met)-null mutant mimicked that of CAX prepupae, but the mutant formed viable adults, which had marked abnormalities in the organization of their optic lobe neuropils. Feeding Met(27) larvae on the JHM diet did not rescue the premature EcR-B1 expression or the downregulation of proliferation but did partially rescue the premature separation of R7, suggesting that other pathways besides Met might be involved in mediating the response to JH. Selective expression of Met RNAi in the photoreceptors caused their premature expression of EcR-B1 and the separation of R7 and R8, but driving Met RNAi in lamina neurons led only to the precocious appearance of EcR-B1 in the lamina. Thus, the lack of JH and its receptor Met causes a heterochronic shift in the development of the visual system that is likely to result from some cells {\textquoteright}misinterpreting{\textquoteright} the ecdysteroid peaks that drive metamorphosis.

}, keywords = {Animals, Basic Helix-Loop-Helix Transcription Factors, Biological, Corpora Allata, Diet, Drosophila melanogaster, Drosophila Proteins, Invertebrate, Juvenile Hormones, Larva, Metamorphosis, Neurons, Nonmammalian, Optic Lobe, Photoreceptor Cells, Pyridines, Receptors, Recombinant Fusion Proteins, RNA Interference, Steroid}, issn = {1477-9129}, doi = {10.1242/dev.037218}, author = {Riddiford, Lynn M and Truman, James W and Mirth, Christen K and Shen, Yu-Chi} } @article {2496, title = {The ecdysone receptor controls the post-critical weight switch to nutrition-independent differentiation in Drosophila wing imaginal discs.}, journal = {Development}, volume = {136}, year = {2009}, month = {2009 Jul}, pages = {2345-53}, abstract = {

In holometabolous insects, a species-specific size, known as critical weight, needs to be reached for metamorphosis to be initiated in the absence of further nutritional input. Previously, we found that reaching critical weight depends on the insulin-dependent growth of the prothoracic glands (PGs) in Drosophila larvae. Because the PGs produce the molting hormone ecdysone, we hypothesized that ecdysone signaling switches the larva to a nutrition-independent mode of development post-critical weight. Wing discs from pre-critical weight larvae [5 hours after third instar ecdysis (AL3E)] fed on sucrose alone showed suppressed Wingless (WG), Cut (CT) and Senseless (SENS) expression. Post-critical weight, a sucrose-only diet no longer suppressed the expression of these proteins. Feeding larvae that exhibit enhanced insulin signaling in their PGs at 5 hours AL3E on sucrose alone produced wing discs with precocious WG, CT and SENS expression. In addition, knocking down the Ecdysone receptor (EcR) selectively in the discs also promoted premature WG, CUT and SENS expression in the wing discs of sucrose-fed pre-critical weight larvae. EcR is involved in gene activation when ecdysone is present, and gene repression in its absence. Thus, knocking down EcR derepresses genes that are normally repressed by unliganded EcR, thereby allowing wing patterning to progress. In addition, knocking down EcR in the wing discs caused precocious expression of the ecdysone-responsive gene broad. These results suggest that post-critical weight, EcR signaling switches wing discs to a nutrition-independent mode of development via derepression.

}, keywords = {Animals, Body Patterning, Cell Differentiation, Developmental, Drosophila, Drosophila Proteins, Gene Expression Regulation, Genes, Genetically Modified, Homeodomain Proteins, Insect, Insulin, Nuclear Proteins, Receptors, Signal Transduction, Steroid, Sucrose, Transcription Factors, Wing, Wnt1 Protein}, issn = {0950-1991}, doi = {10.1242/dev.032672}, author = {Mirth, Christen K and Truman, James W and Riddiford, Lynn M} } @article {2502, title = {Larval leg integrity is maintained by distal-less and is required for proper timing of metamorphosis in the flour beetle, tribolium castaneum.}, journal = {Developmental Biology}, volume = {326}, year = {2009}, month = {2009 Feb 1}, pages = {60-7}, abstract = {

The dramatic transformation from a larva to an adult must be accompanied by a coordinated activity of genes and hormones that enable an orchestrated transformation from larval to pupal/adult tissues. The maintenance of larval appendages and their subsequent transformation to appendages in holometabolous insects remains elusive at the developmental genetic level. Here the role of a key appendage patterning gene Distal-less (Dll) was examined in mid- to late-larval stages of the flour beetle, Tribolium castaneum. During late larval development, Dll was expressed in appendages in a similar manner as previously reported for the tobacco hornworm, Manduca sexta. Removal of this late Dll expression resulted in disruption of adult appendage patterning. Intriguingly, earlier removal resulted in dramatic loss of structural integrity and identity of larval appendages. A large amount of variability in appendage morphology was observed following Dll dsRNA injection, unlike larvae injected with dachshund dsRNA. These Dll dsRNA-injected larvae underwent numerous supernumerary molts, which could be terminated with injection of either JH methyltransferase or Methoprene-tolerant dsRNA. Apparently, the partial dedifferentiation of the appendages in these larvae acts to maintain high JH and, hence, prevents metamorphosis.

}, keywords = {Animals, Biological, Double-Stranded, Extremities, Homeodomain Proteins, Larva, Metamorphosis, Methoprene, RNA, Transcription Factors, Tribolium}, issn = {1095-564X}, doi = {10.1016/j.ydbio.2008.10.022}, author = {Suzuki, Yuichiro and Squires, Diego C and Riddiford, Lynn M} } @article {2497, title = {The molecular mechanisms of cuticular melanization: the ecdysone cascade leading to dopa decarboxylase expression in Manduca sexta.}, journal = {Insect Biochemistry and Molecular Biology}, volume = {39}, year = {2009}, month = {2009 Apr}, pages = {245-53}, abstract = {

Many insect developmental color changes are known to be regulated by both ecdysone and juvenile hormone. Yet the molecular mechanisms underlying this regulation have not been well understood. This review highlights the hormonal mechanisms involved in the regulation of two key enzymes [dopa decarboxylase (DDC) and phenoloxidase] necessary for insect cuticular melanization, and the molecular action of 20-hydroxyecdysone on various transcription factors leading to DDC expression at the end of a larval molt in Manduca sexta. In addition, the ecdysone cascade found in M. sexta is compared with that of other organisms.

}, keywords = {Animals, Developmental, Dopa Decarboxylase, Ecdysone, Gene Expression Regulation, Insect Proteins, Manduca, Melanins}, issn = {1879-0240}, doi = {10.1016/j.ibmb.2009.01.008}, author = {Hiruma, Kiyoshi and Riddiford, Lynn M} } @article {2501, title = {The nuclear receptor E75A has a novel pair-rule-like function in patterning the milkweed bug, Oncopeltus fasciatus.}, journal = {Developmental Biology}, volume = {334}, year = {2009}, month = {2009 Oct 1}, pages = {300-10}, abstract = {

Genetic studies of the fruit fly Drosophila have revealed a hierarchy of segmentation genes (maternal, gap, pair-rule and HOX) that subdivide the syncytial blastoderm into sequentially finer-scale coordinates. Within this hierarchy, the pair-rule genes translate gradients of information into periodic stripes of expression. How pair-rule genes function during the progressive mode of segmentation seen in short and intermediate-germ insects is an ongoing question. Here we report that the nuclear receptor Of{\textquoteright}E75A is expressed with double segment periodicity in the head and thorax. In the abdomen, Of{\textquoteright}E75A is expressed in a unique pattern during posterior elongation, and briefly resembles a sequence that is typical of pair-rule genes. Depletion of Of{\textquoteright}E75A mRNA caused loss of a subset of odd-numbered parasegments, as well as parasegment 6. Because these parasegments straddle segment boundaries, we observe fusions between adjacent segments. Finally, expression of Of{\textquoteright}E75A in the blastoderm requires even-skipped, which is a gap gene in Oncopeltus. These data show that the function of Of{\textquoteright}E75A during embryogenesis shares many properties with canonical pair-rule genes in other insects. They further suggest that parasegment specification may occur through irregular and episodic pair-rule-like activity.

}, keywords = {Animals, Blastoderm, Body Patterning, Cytoplasmic and Nuclear, Embryo, Hemiptera, Insect Proteins, Nonmammalian, Receptors, RNA Interference}, issn = {1095-564X}, doi = {10.1016/j.ydbio.2009.06.038}, author = {Erezyilmaz, Deniz F and Kelstrup, Hans C and Riddiford, Lynn M} } @article {2500, title = {The role of the pupal determinant broad during embryonic development of a direct-developing insect.}, journal = {Development Genes \& Evolution}, volume = {219}, year = {2009}, month = {2009 Dec 30}, pages = {535-44}, abstract = {

Metamorphosis is one of the most common, yet dramatic of life history strategies. In insects, complete metamorphosis with morphologically distinct larval stages arose from hemimetabolous ancestors that were more direct developing. Over the past century, several ideas have emerged that suggest the holometabolous pupa is developmentally homologous to the embryonic stages of the hemimetabolous ancestor. Other theories consider the pupal stage to be a modification of a hemimetabolous nymph. To address this question, we have isolated an ortholog of the pupal determinant, broad (br), from the hemimetabolous milkweed bug and examined its role during embryonic development. We show that Oncopeltus fasciatus br (Of{\textquoteright}br) is expressed in two phases. The first occurs during germ band invagination and segmentation when Of{\textquoteright}br is expressed ubiquitously in the embryonic tissues. The second phase of Of{\textquoteright}br expression appears during the pronymphal phase of embryogenesis and persists through nymphal differentiation to decline just before hatching. Knock-down of Of{\textquoteright}br transcripts results in defects that range from posterior truncations in the least-affected phenotypes to completely fragmented embryonic tissues in the most severe cases. Analysis of the patterning genes engrailed and hunchback reveal loss of segments and a failure in neural differentiation after Of{\textquoteright}br depletion. Finally, we show that br is constitutively expressed during embyrogenesis of the ametabolous firebrat, Thermobia domestica. This suggests that br expression is prominent during embryonic development of ametabolous and hemimetabolous insects but was lost with the emergence of the completely metamorphosing insects.

}, keywords = {Animals, Biological, Biological Evolution, Body Patterning, Cloning, Developmental, DNA Primers, Drosophila Proteins, Gene Expression Regulation, Heteroptera, In Situ Hybridization, Insect Proteins, Metamorphosis, Molecular, Reverse Transcriptase Polymerase Chain Reaction, Transcription Factors}, issn = {1432-041X}, doi = {10.1007/s00427-009-0315-7}, author = {Erezyilmaz, Deniz F and Rynerson, Melody R and Truman, James W and Riddiford, Lynn M} } @article {2495, title = {Temporal patterns of broad isoform expression during the development of neuronal lineages in Drosophila.}, journal = {Neural Development}, volume = {4}, year = {2009}, month = {2009 Nov 2}, pages = {39}, abstract = {

During the development of the central nervous system (CNS) of Drosophila, neuronal stem cells, the neuroblasts (NBs), first generate a set of highly diverse neurons, the primary neurons that mature to control larval behavior, and then more homogeneous sets of neurons that show delayed maturation and are primarily used in the adult. These latter, {\textquoteright}secondary{\textquoteright} neurons show a complex pattern of expression of broad, which encodes a transcription factor usually associated with metamorphosis, where it acts as a key regulator in the transitions from larva and pupa.

}, keywords = {Animals, Biological, Drosophila, Drosophila Proteins, Genetically Modified, Interneurons, Metamorphosis, Motor Neurons, Mushroom Bodies, Neurites, Neurons, Newborn, Nonmammalian, Optic Lobe, Protein Isoforms, Thorax, Time Factors, Transcription Factors}, issn = {1749-8104}, doi = {10.1186/1749-8104-4-39}, author = {Zhou, Baohua and Williams, Darren W and Altman, Janet and Riddiford, Lynn M and Truman, James W} } @article {2503, title = {Insulin/IGF signaling regulates the change in commitment in imaginal discs and primordia by overriding the effect of juvenile hormone.}, journal = {Developmental Biology}, volume = {324}, year = {2008}, month = {2008 Dec 15}, pages = {258-65}, abstract = {

At the beginning of the final larval (fifth) instar of Manduca sexta, imaginal precursors including wing discs and eye primordia initiate metamorphic changes, such as pupal commitment, patterning and cell proliferation. Juvenile hormone (JH) prevents these changes in earlier instars and in starved final instar larvae, but nutrient intake overcomes this effect of JH in the latter. In this study, we show that a molecular marker of pupal commitment, broad, is up-regulated in the wing discs by feeding on sucrose or by bovine insulin or Manduca bombyxin in starved final instar larvae. This effect of insulin could not be prevented by JH. In vitro insulin had no effect on broad expression but relieved the suppression of broad expression by JH. This effect of insulin was directly on the disc as shown by its reduction in the presence of insulin receptor dsRNA. In starved penultimate fourth instar larvae, broad expression in the wing disc was not up-regulated by insulin. The discs became responsive to this action of insulin during the molt to the fifth instar together with the ability to become pupally committed in response to 20-hydroxyecdysone. Thus, the Manduca bombyxin acts as a metamorphosis-initiating factor in the imaginal precursors.

}, keywords = {Animals, Cells, Cloning, Cultured, Developmental, Ecdysterone, Gene Expression Regulation, Insect Proteins, Insulin, Juvenile Hormones, Larva, Manduca, Messenger, Molecular, Receptor, RNA, RNA Interference, Signal Transduction, Somatomedins, Sucrose, Wing}, issn = {1095-564X}, doi = {10.1016/j.ydbio.2008.09.017}, author = {Koyama, Takashi and Syropyatova, Maria O and Riddiford, Lynn M} } @article {2499, title = {Juvenile hormone action: a 2007 perspective.}, journal = {Journal of Insect Physiology}, volume = {54}, year = {2008}, month = {2008 Jun}, pages = {895-901}, abstract = {

Juvenile hormone (JH) is a key hormone in regulation of the insect{\textquoteright}s life history, both in maintaining the larval state during molts and in directing reproductive maturation. This short review highlights the recent papers of the past year that lend new insight into the role of this hormone in the larva and the mechanisms whereby it achieves this role.

}, keywords = {Animals, Basic Helix-Loop-Helix Transcription Factors, Biological, DNA-Binding Proteins, Drosophila Proteins, Insects, Juvenile Hormones, Larva, Metamorphosis, Response Elements, Transcription Factors}, issn = {0022-1910}, doi = {10.1016/j.jinsphys.2008.01.014}, author = {Riddiford, Lynn M} } @article {2504, title = {Kr{\"u}ppel homolog 1 (Kr-h1) mediates juvenile hormone action during metamorphosis of Drosophila melanogaster.}, journal = {Mechanisms of Development}, volume = {125}, year = {2008}, month = {2008 Jan-Feb}, pages = {91-105}, abstract = {

Juvenile hormone (JH) given at pupariation inhibits bristle formation and causes pupal cuticle formation in the abdomen of Drosophila melanogaster due to its prolongation of expression of the transcription factor Broad (BR). In a microarray analysis of JH-induced gene expression in abdominal integument, we found that Kr{\"u}ppel homolog 1 (Kr-h1) was up-regulated during most of adult development. Quantitative real-time PCR analyses showed that Kr-h1 up-regulation began at 10h after puparium formation (APF), and Kr-h1 up-regulation occurred in imaginal epidermal cells, persisting larval muscles, and larval oenocytes. Ectopic expression of Kr-h1 in abdominal epidermis using T155-Gal4 to drive UAS-Kr-h1 resulted in missing or short bristles in the dorsal midline. This phenotype was similar to that seen after a low dose of JH or after misexpression of br between 21 and 30 h APF. Ectopic expression of Kr-h1 prolonged the expression of BR protein in the pleura and the dorsal tergite. No Kr-h1 was seen after misexpression of br. Thus, Kr-h1 mediates some of the JH signaling in the adult abdominal epidermis and is upstream of br in this pathway. We also show for the first time that the JH-mediated maintenance of br expression in this epidermis is patterned and that JH delays the fusion of the imaginal cells and the disappearance of Dpp in the dorsal midline.

}, keywords = {Animals, Base Sequence, Biological, DNA Primers, Drosophila melanogaster, Drosophila Proteins, Kruppel-Like Transcription Factors, Larva, Metamorphosis, Oligonucleotide Array Sequence Analysis, Polymerase Chain Reaction, Up-Regulation}, issn = {0925-4773}, doi = {10.1016/j.mod.2007.10.002}, author = {Minakuchi, Chieka and Zhou, Xiaofeng and Riddiford, Lynn M} } @article {2505, title = {The role of Broad in the development of Tribolium castaneum: implications for the evolution of the holometabolous insect pupa.}, journal = {Development (Cambridge, England)}, volume = {135}, year = {2008}, month = {2008 Feb}, pages = {569-77}, abstract = {

The evolution of complete metamorphosis in insects is a key innovation that has led to the successful diversification of holometabolous insects, yet the origin of the pupa remains an enigma. Here, we analyzed the expression of the pupal specifier gene broad (br), and the effect on br of isoform-specific, double-stranded RNA-mediated silencing, in a basal holometabolous insect, the beetle Tribolium castaneum. All five isoforms are weakly expressed during the penultimate instar and highly expressed during the prepupal period of the final instar. Application of hydroprene, a juvenile hormone analog, during the penultimate instar caused a repeat of the penultimate br expression patterns, and the formation of supernumerary larvae. Use of dsRNA against the br core region, or against a pair of either the br-Z2 or br-Z3 isoform with the br-Z1 or br-Z4 isoform, produced mobile animals with well-differentiated adult-like appendages, but which retained larval-like urogomphi and epidermis. Disruption of either the br-Z2 or the br-Z3 isoform caused the formation of shorter wings. Disruption of both br-Z1 and br-Z4 caused the appearance of pupal traits in the adults, but disruption of br-Z5 had no morphological effect. Our findings show that the br isoform functions are broadly conserved within the Holometabola and suggest that evolution of br isoform expression may have played an important role in the evolution of the pupa in holometabolous insects.

}, keywords = {Animals, Biological Evolution, Developmental, Double-Stranded, Fatty Acids, Gene Expression Profiling, Gene Expression Regulation, Genes, Insect, Insect Proteins, Larva, Phenotype, Protein Isoforms, Pupa, RNA, RNA Interference, Tribolium, Unsaturated}, issn = {0950-1991}, doi = {10.1242/dev.015263}, author = {Suzuki, Yuichiro and Truman, James W and Riddiford, Lynn M} } @article {2506, title = {The coordination of the sequential appearance of MHR4 and dopa decarboxylase during the decline of the ecdysteroid titer at the end of the molt.}, journal = {Molecular and Cellular Endocrinology}, volume = {276}, year = {2007}, month = {2007 Sep 30}, pages = {71-9}, abstract = {

During the last larval molt in Manduca sexta, in response to an increasing, then decreasing ecdysteroid titer, a number of transcription factors such as E75B, MHR3, MHR4, and betaFTZ-F1 appear and disappear in the abdominal epidermis leading to dopa decarboxylase (DDC) expression. Messenger RNAs for both the 20E-induced transcription factors, MHR3 and E75B, are maximal near the peak of the ecdysteroid titer with MHR4 mRNA appearing as the titer declines followed by betaFTZ-F1 and DDC mRNAs. E75B and MHR4 mRNA were not expressed in Manduca GV1 cells, either during exposure to 20E or after its removal. When either MHR3 dsRNA was transfected or E75B was constitutively expressed in these cells, MHR4 mRNA appeared in response to 20E by 6h. E75B was found to form a heterodimer with MHR3 using the BacterioMatch II two-hybrid assay. We conclude that MHR3 apparently suppresses MHR4 expression in the presence of 20E; the appearance of E75B then removes MHR3 by dimerization, allowing MHR4 to be expressed. Because of significant basal activity of the ddc promoter in the GV1 cells, we could perform rescue experiments by adding various factors. Constitutive expression of either E75B or MHR4 in the cells suppressed the significant basal activity of the 3.2kb ddc promoter in the GV1 cells, but 20E had no effect on this activity. Thus, E75B and MHR4 are 20E-induced inhibitory factors that suppress ddc expression and therefore act as ecdysteroid-regulated timers to coordinate the onset of ddc expression at the end of the molt.

}, keywords = {Animals, Biological, Cell Line, Cytoplasmic and Nuclear, Developmental, Dopa Decarboxylase, Ecdysteroids, Gene Expression Regulation, Genetic, Insect Proteins, Manduca, Models, Molting, Promoter Regions, Protein Binding, Receptors}, issn = {0303-7207}, doi = {10.1016/j.mce.2007.07.002}, author = {Hiruma, Kiyoshi and Riddiford, Lynn M} } @article {2507, title = {Size assessment and growth control: how adult size is determined in insects.}, journal = {BioEssays: News and Reviews in Molecular, Cellular and Developmental Biology}, volume = {29}, year = {2007}, month = {2007 Apr}, pages = {344-55}, abstract = {

Size control depends on both the regulation of growth rate and the control over when to stop growing. Studies of Drosophila melanogaster have shown that insulin and Target of Rapamycin (TOR) pathways play principal roles in controlling nutrition-dependent growth rates. A TOR-mediated nutrient sensor in the fat body detects nutrient availability, and regulates insulin signaling in peripheral tissues, which in turn controls larval growth rates. After larvae initiate metamorphosis, growth stops. For growth to stop at the correct time, larvae need to surpass a critical weight. Recently, it was found that the insulin-dependent growth of the prothoracic gland is involved in assessing when critical weight has been reached. Furthermore, mutations in DHR4, a repressor of ecdysone signaling, reduce critical weight and adult size. Thus, the mechanisms that control growth rates converge on those assessing size to ensure that the larvae attain the appropriate size at metamorphosis.

}, keywords = {Aging, Animals, Body Size, Hormones, Insects, Signal Transduction}, issn = {0265-9247}, doi = {10.1002/bies.20552}, author = {Mirth, Christen Kerry and Riddiford, Lynn M} } @article {2446, title = {The pupal specifier broad directs progressive morphogenesis in a direct-developing insect.}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {103}, year = {2006}, month = {2006 May 2}, pages = {6925-30}, abstract = {

A key regulatory gene in metamorphosing (holometabolous) insect life histories is the transcription factor broad (br), which specifies pupal development. To determine the role of br in a direct-developing (hemimetabolous) insect that lacks a pupal stage, we cloned br from the milkweed bug, Oncopeltus fasciatus (Of{\textquoteright}br). We find that, unlike metamorphosing insects, in which br expression is restricted to the larval-pupal transition, Of{\textquoteright}br mRNA is expressed during embryonic development and is maintained at each nymphal molt but then disappears at the molt to the adult. Induction of a supernumerary nymphal stage with a juvenile hormone (JH) mimic prevented the disappearance of br mRNA. In contrast, induction of a precocious adult molt by application of precocene II to third-stage nymphs caused a loss of br mRNA at the precocious adult molt. Thus, JH is necessary to maintain br expression during the nymphal stages. Injection of Of{\textquoteright}br dsRNA into either early third- or fourth-stage nymphs caused a repetition of stage-specific pigmentation patterns and prevented the normal anisometric growth of the wing pads without affecting isometric growth or molting. Therefore, br is necessary for the mutable (heteromorphic) changes that occur during hemimetabolous development. Our results suggest that metamorphosis in insects arose as expression of br, which conveys competence for change, became restricted to one postembryonic instar. After this shift in br expression, the progressive changes that occur within the nymphal series in basal insects became compressed to the one short period of morphogenesis seen in the larva-to-pupa transition of holometabolous insects.

}, keywords = {Animals, Biological, Drosophila Proteins, Heteroptera, Insect Proteins, Juvenile Hormones, Metamorphosis, Molecular Sequence Data, Morphogenesis, Nymph, Pigmentation, RNA, Transcription Factors, Wing}, issn = {0027-8424}, doi = {10.1073/pnas.0509983103}, author = {Erezyilmaz, Deniz F and Riddiford, Lynn M and Truman, James W} } @article {2447, title = {The role of the prothoracic gland in determining critical weight for metamorphosis in Drosophila melanogaster.}, journal = {Current Biology}, volume = {15}, year = {2005}, month = {2005 Oct 25}, pages = {1796-807}, abstract = {

The timely onset of metamorphosis in holometabolous insects depends on their reaching the appropriate size known as critical weight. Once critical weight is reached, juvenile hormone (JH) titers decline, resulting in the release of prothoracicotropic hormone (PTTH) at the next photoperiod gate and thereby inducing metamorphosis. How individuals determine when they have reached critical weight is unknown. We present evidence that in Drosophila, a component of the ring gland, the prothoracic gland (PG), assesses growth to determine when critical weight has been achieved.

}, keywords = {Animals, Biological, Body Weight, Developmental, Drosophila, Drosophila Proteins, Ecdysteroids, Endocrine Glands, Gene Expression Regulation, Immunoenzyme Techniques, Insect Hormones, Insulin, Larva, Metamorphosis, PTEN Phosphohydrolase}, issn = {0960-9822}, doi = {10.1016/j.cub.2005.09.017}, author = {Mirth, Christen and Truman, James W and Riddiford, Lynn M} } @article {2512, title = {Differential control of MHR3 promoter activity by isoforms of the ecdysone receptor and inhibitory effects of E75A and MHR3.}, journal = {Developmental Biology}, volume = {272}, year = {2004}, month = {2004 Aug 15}, pages = {510-21}, abstract = {

MHR3 is an ecdysone-inducible transcription factor whose expression in both Manduca sexta epidermis and the Manduca GV1 cell line is induced by 20-hydroxyecdysone (20E) in vitro. There are four putative ecdysone response elements (EcRE) in the 2.6-kb flanking region of the MHR3 promoter. The most proximal, EcRE1, is necessary for activation of the promoter by 20E in the GV1 cells because the mutation of EcRE1 caused the loss of responsiveness to 20E. Previous studies showed that EcR-B1/USP-1 bound only to EcRE1 and high levels of this complex increased the 20E-induced activation, whereas the presence of high USP-2 prevented this increased activation. When we expressed EcR-A alone or in combination with USP-1 under the control of Autographa californica baculovirus promoter (pIE1hr), the activation of the 2.6-kb promoter by 20E was reduced by about 50\%. Moreover, when EcR-A was expressed together with both EcR-B1 and USP-1, it reduced the normal activation caused by EcR-B1 and USP-1 by 50\%. Gel mobility shift assays showed no binding of EcR-A/USP-1 to EcRE1. The presence of EcR-A, however, reduced the binding of EcR-B1/USP-1 by about 50\%. These findings suggest that EcR-A competes with EcR-B1 for binding of USP-1, leading to a decline in activity of the promoter. In addition, E75A, another ecdysone-induced transcription factor, and MHR3 itself suppressed MHR3 promoter activity by binding to the monomeric response element (MRE2). Therefore, MHR3 can be down-regulated both by itself and by E75A.

}, keywords = {Animals, Base Sequence, Binding Sites, Cell Line, DNA-Binding Proteins, Ecdysterone, Epidermis, Gene Expression Regulation, Genetic, Glycoproteins, Insect Proteins, Manduca, Molecular Sequence Data, Mutation, Promoter Regions, Protein Isoforms, Receptors, Response Elements, Serpins, Steroid, Transcription Factors}, issn = {0012-1606}, doi = {10.1016/j.ydbio.2004.04.028}, author = {Hiruma, Kiyoshi and Riddiford, Lynn M} } @article {2513, title = {Overexpression of broad: a new insight into its role in the Drosophila prothoracic gland cells.}, journal = {The Journal of Experimental Biology}, volume = {207}, year = {2004}, month = {2004 Mar}, pages = {1151-61}, abstract = {

Insect molting is triggered by ecdysteroids, which are produced in the prothoracic glands (PG). The broad (br) gene is one of the {\textquoteright}early genes{\textquoteright} directly regulated by ecdysteroids. Ectopic expression of the BR-Z3 isoform in early second instar Drosophila larvae (L2) before the rise of the ecdysteroid titer prevented molting to the third instar, but the larvae subsequently formed L2 prepupae after prolonged feeding. When these larvae were fed on diet containing 20-hydroxyecdysone (20E), they formed pharate third instar larvae. The critical weight for normal L3 pupariation of w(1118) larvae was found to be 0.8 mg and that for L2 pupariation was 0.45 mg. We also defined a threshold weight for metamorphosis of 0.3 mg, above which L2 larvae will metamorphose when provided with 20E. BR-Z3 apparently works through the PG cells of the ring gland but not the putative neurosecretory cells that drive ecdysone secretion, because ectopic expression of BR-Z3 specifically in the ring gland caused 53\% of the larvae to become permanent first instar larvae. Driving other BR isoforms in the ring gland prevented larval molting or pupariation to varying degrees. These molting defects were rescued by feeding 20E. Overexpression of each of the BR isoforms caused degeneration of the PG cells but on different time courses, indicating that BR is a signal for the degeneration of the PG cells that normally occurs during the pupal-adult transition.

}, keywords = {Animals, Body Weights and Measures, Drosophila, Drosophila Proteins, Ecdysterone, Exocrine Glands, Gene Expression Regulation, Genetically Modified, Immunohistochemistry, Larva, Molting, Protein Isoforms, Transcription Factors}, issn = {0022-0949}, author = {Zhou, Xiaofeng and Zhou, Baohua and Truman, James W and Riddiford, Lynn M} } @article {2514, title = {E74 exhibits stage-specific hormonal regulation in the epidermis of the tobacco hornworm, manduca sexta.}, journal = {Developmental Biology}, volume = {258}, year = {2003}, month = {2003 Jun 1}, pages = {76-90}, abstract = {

The transcription factor E74 is one of the early genes induced by ecdysteroids during metamorphosis of Drosophila melanogaster. Here, we report the cloning and hormonal regulation of E74 from the tobacco hornworm, Manduca sexta (MsE74). MsE74 is 98\% identical to that of D. melanogaster within the DNA-binding ETS domain of the protein. The 5{\textquoteright}-isoform-specific regions of MsE74A and MsE74B share significantly lower sequence similarity (30-40\%). Developmental expression by Northern blot analysis reveals that, during the 5th larval instar, MsE74B expression correlates with pupal commitment on day 3 and is induced to maximal levels within 12h by low levels of 20-hydroxyecdysone (20E) and repressed by physiologically relevant levels of juvenile hormone I (JH I). Immunocytochemical analysis shows that MsE74B appears in the epidermis before the 20E-induced Broad transcription factor that is correlated with pupal commitment (Zhou and Riddiford, 2001). In contrast, MsE74A is expressed late in the larval and the pupal molts when the ecdysteroid titer has declined to low levels and in the adult molt just as the ecdysteroid titer begins to decline. This change in timing during the adult molt appears not to be due to the absence of JH as there was no change during the pupal molt of allatectomized animals. When either 4th or 5th instar larval epidermis was explanted and subjected to hormonal manipulations, MsE74A induction occurred only after exposure to 20E followed by its removal. Thus, MsE74B appears to have a similar role at the onset of metamorphosis in Manduca as it does in Drosophila, whereas MsE74A is regulated differently at pupation in Manduca than at pupariation in Drosophila.

}, keywords = {Amino Acid, Amino Acid Sequence, Animals, Base Sequence, Biological, Cells, Cultured, Developmental, Drosophila, Ecdysterone, Epidermis, Gene Expression Regulation, Genes, Insect, Insect Proteins, Juvenile Hormones, Larva, Manduca, Messenger, Metamorphosis, Molecular Sequence Data, Open Reading Frames, Protein Isoforms, Protein Structure, Pupa, RNA, Sequence Homology, Tertiary, Transcription Factors}, issn = {0012-1606}, author = {Stilwell, Geoffrey E and Nelson, Charles A and Weller, John and Cui, Haiyang and Hiruma, Kiyoshi and Truman, James W and Riddiford, Lynn M} } @article {2515, title = {Broad specifies pupal development and mediates the {\textquoteright}status quo{\textquoteright} action of juvenile hormone on the pupal-adult transformation in Drosophila and Manduca.}, journal = {Development }, volume = {129}, year = {2002}, month = {2002 May}, pages = {2259-69}, abstract = {

The understanding of the molecular basis of the endocrine control of insect metamorphosis has been hampered by the profound differences in responses of the Lepidoptera and the Diptera to juvenile hormone (JH). In both Manduca and Drosophila, the broad (br) gene is expressed in the epidermis during the formation of the pupa, but not during adult differentiation. Misexpression of BR-Z1 during either a larval or an adult molt of Drosophila suppressed stage-specific cuticle genes and activated pupal cuticle genes, showing that br is a major specifier of the pupal stage. Treatment with a JH mimic at the onset of the adult molt causes br re-expression and the formation of a second pupal cuticle in Manduca, but only in the abdomen of Drosophila. Expression of the BR isoforms during adult development of Drosophila suppressed bristle and hair formation when induced early or redirected cuticle production toward the pupal program when induced late. Expression of BR-Z1 at both of these times mimicked the effect of JH application but, unlike JH, it caused production of a new pupal cuticle on the head and thorax as well as on the abdomen. Consequently, the {\textquoteright}status quo{\textquoteright} action of JH on the pupal-adult transformation is mediated by the JH-induced re-expression of BR.

}, keywords = {Animals, Developmental, Drosophila, Gene Expression Regulation, Genes, Insect, Juvenile Hormones, Manduca, Messenger, Protein Isoforms, Pupa, RNA, Species Specificity}, issn = {0950-1991}, author = {Zhou, Xiaofeng and Riddiford, Lynn M} }