@proceedings {45794, title = {Potential Patterning Differences Underlying Oviparous and Viviparous Development in the Pea Aphid}, volume = {53}, year = {2013}, month = {01/2013}, pages = {E247-E247}, publisher = {OXFORD UNIV PRESS INC}, abstract = {

The pea aphid, Acyrthosiphon pisum, exhibits several environmentally cued, discrete, alternate phenotypes (polyphenisms) during its life cycle. In the case of the reproductive polyphenism, differences in day length determine whether mothers will produce daughters that reproduce either sexually by laying fertilized eggs (oviparous sexual reproduction), or asexually by allowing oocytes to complete embryogenesis within the mother without fertilization (viviparous parthenogenesis). Oocytes and embryos that are produced asexually develop more rapidly, are yolk-free, and much smaller than oocytes and embryos that are produced sexually. Perhaps most striking, the process of oocyte differentiation is truncated in the case of asexual/viviparous development, potentially precluding interactions between the oocyte and surrounding follicle cells that might take place during sexual/oviparous development. Given the important patterning roles that oocyte-follicle cell interactions play in Drosophila, these overt differences suggest that there may be underlying differences in the molecular mechanisms of pattern formation. We have found differences in the expression of homologs of torso-like and tailless, as well as activated MAP kinase, suggesting that there are important differences in the hemipteran version of the terminal patterning system between viviparous and oviparous development. Establishing such differences in the expression of patterning genes between these developmental modes is a first step toward understanding how a single genome manages to direct patterning events in such different embryological contexts.

}, url = {http://www.sicb.org/meetings/2013/schedule/abstractdetails.php?id=1253}, author = {R Bickel and H Cleveland and J Barkas and N Belletier and DL Stern and GK Davis} } @proceedings {45797, title = {A patterning difference underlying viviparous and oviparous development in the pea aphid}, volume = {50}, year = {2010}, month = {01/2010}, pages = {E205-E205}, publisher = {OXFORD UNIV PRESS INC}, abstract = {

The pea aphid, Acyrthosiphon pisum, exhibits several environmentally cued, discrete, alternate phenotypes (polyphenisms) during its life cycle. In the case of the reproductive polyphenism, differences in day length determine whether mothers will produce daughters that reproduce either sexually by laying fertilized eggs (oviparous sexual reproduction), or asexually by allowing oocytes to complete embryogenesis within the mother without fertilization (viviparous parthenogenesis). Oocytes and embryos that are produced asexually and develop within the mother develop more rapidly, are yolk-free, and much smaller than oocytes and embryos that are produced sexually. These overt differences suggest that there may be underlying differences in the molecular mechanisms of pattern formation. Indeed, our preliminary comparative gene expression work suggests that there are important differences in the terminal patterning system, involving the Torso pathway, between viviparous and oviparous development. We have so far examined the expression of homologs of torso-like and capicua, members of the Drosophila Torso pathway. We have detected clear differential expression of torso-like and possible differential expression of capicua. Establishing such differences in the expression of patterning genes between these developmental modes is a first step toward understanding how a single genome manages to direct patterning events in such different embryological contexts.

}, author = {R Bickel and N Belletier and H Cleveland and DL Stern and G Davis} } @proceedings {45798, title = {Molecular Basis of Facultative Asexuality in Aphids}, volume = {49}, year = {2009}, month = {01/2009}, pages = {E308-E308}, publisher = {OXFORD UNIV PRESS INC}, abstract = {

Phenotypic plasticity allows organisms to quickly adapt in response to changing environments. Little is known of the genetic, environmental and epigenetic contribution to the expression of alternative adaptive developmental outcomes. We study aphid polyphenisms, which offer a unique, compelling opportunity to study multiple levels of biological organization, especially insect epigenetics. The pea aphid, Acyrthosiphon pisum, exhibits an adaptive reproductive polyphenism whereby genetically identical individuals reproduce either sexually (meiosis) or asexually (parthenogenesis) depending on environmental conditions during maternal development (short or long photoperiod, respectively). To understand how facultative asexuality evolved in aphids, we first determined meiosis gene activity in sexuals and asexuals. I determined that the pea aphid genome encodes single copies of homologs for the majority of the core meiotic machinery, suggesting that meiotic plasticity is not due simply to gene loss or expansion. Next, we determined if these core meiosis genes are expressed using PCR spanning across at least one intron from cDNA isolated from asexual and sexual ovaries. Surprisingly, meiosis specific genes (e.g., Spo11, Msh4, Msh5, Hop2 and Mnd1) are expressed in not only in asexual ovaries but also in somatic tissue and an obligately asexual aphid strain. Interestingly, the Spo11 PCR product contained intronic sequence, thus representing unspliced mRNA. Germline expression of Spo11, Mnd1 and Hop2 was confirmed by in situ analysis. Preliminary results identified candidate methylation sites in the Spo11 locus, indicating an epigenetic basis for this expression difference. Further characterization will help us better understand the molecular and epigenetic mechanisms underlying this adaptive facultative plasticity.

}, url = {http://www.sicb.org/meetings/2009/schedule/abstractdetails.php3?id=1224}, author = {DG Srinivasan and L Ano and GK Davis and DL Stern} } @proceedings {45799, title = {Gene expression patterns underlying wing polyphenism and polymorphism in the pea aphid}, volume = {46}, year = {2007}, month = {01/2007}, pages = {E186-E186}, publisher = {OXFORD UNIV PRESS INC}, abstract = {

The pea aphid, Acyrthosiphon pisum, exhibits several environmentally cued, discrete, alternate phenotypes (polyphenisms) during its life cycle. In the wing polyphenism, female progeny develop as either winged or unwinged depending on the extent of crowding or host plant quality experienced by the mother. Males also have the ability to develop as either winged or unwinged, but this is genetically determined by a single locus on the X chromosome and is thus referred to as a wing polymorphism. In order to gain insight into the patterns of gene expression that underlie the wing polyphenism and polymorphism we have used a pea aphid cDNA microarray to examine gene expression in winged and unwinged females and males. Results suggest that winged and unwinged morphs exhibit systemic differences in gene expression and that many of these differences are shared between the wing polyphenism and polymorphism (i.e., between females and males). In addition, adult winged and unwinged males exhibit pronounced differences when compared to adult females and fourth instar males, as well as to each other.

}, url = {http://www.sicb.org/meetings/2007/schedule/abstractdetails.php3?id=649}, author = {GK Davis and JA Brisson and DL Stern} } @conference {45802, title = {Prospects in aphid genetics}, booktitle = {Aphids in a new millennium. Proceedings of the Sixth International Symposium on Aphids}, year = {2004}, month = {09/2004}, publisher = {Institut National de la Recherche Agronomique}, organization = {Institut National de la Recherche Agronomique}, address = {Rennes, France}, abstract = {

This paper identifies the prospects of using aphid species as ideal genetic model systems for the study of evolutionary developmental biology and genetic control of polyphenisms. The advantages and disadvantages of using aphids as genetic model organisms are discussed.

}, isbn = {2-7380-1113-6}, url = {http://www.cabdirect.org/abstracts/20043046841.html;jsessionid=4C6865DD4D971042FEB329F0DD6166E5}, author = {DL Stern and JC Simon and CA Dedryver and C Rispe and M Hull{\'e}} } @proceedings {45804, title = {Morphogenesis and gene expressions in the parthenogenetic embryogenesis of the pea aphid Acyrthosiphon pisum}, volume = {17}, year = {2000}, pages = {66}, publisher = {社団法人日本動物学会}, issn = {02890003}, url = {http://ci.nii.ac.jp/naid/110003371583/}, author = {T Miura and S Kambhampati and DL Stern} } @article {45806, title = {Behavior and morphology of monomorphic soldiers from the aphid genus Pseudoregma (Cerataphidini, Hormaphididae): implications for the evolution of morphological castes in social aphids}, journal = {Insectes Sociaux}, volume = {44}, year = {1997}, month = {11/1997}, pages = {379-392}, abstract = {

Soldier-producing aphids have evolved at least nine separate times. The larvae of soldier-producing species can be organized into three general categories: monomorphic larvae, dimorphic larvae with a reproductive soldier caste, and dimorphic larvae with a sterile soldier caste. Here we report the discovery of a novel soldier type in an undescribed species of Pseudoregma that is morphologically similar to P. bambucicola. A colony of this species produced morphologically monomorphic first-instar larvae with a defensive behavioral dimorphism. These larvae attacked natural predators, and larval response to a simple assay, placing the tips of forceps in front of larvae, was correlated with this attacking behavior. Approximately one third of the first-instar larvae in the colony attacked and this proportion was uncorrelated with the time of day, the ambient temperature, or the diel migratory behavior of the aphids. Migrating larvae rarely attacked. Attacking behavior was correlated with another defensive behavior, hind-leg waving. Attackers were more likely to possess the next-instar skin, suggesting that they were older than non-attackers. This is the first example of a possible within-instar age polyethism in soldier-producing aphids. Canonical variates analysis of seven morphological measurements failed to discriminate between attacking and non-attacking larvae. The monomorphic larvae share some morphometric characteristics in common with the soldiers of P. bambucicola and other characteristics in common with normal larvae. We discuss these results with respect to the evolution and loss of soldier castes in the tribe Cerataphidini.

}, keywords = {castes, dimorphism, morphometrics, Soldier aphids}, issn = {0020-1812}, doi = {10.1007/s000400050059}, author = {DL Stern and JA Whitfield and WA Foster} } @article {45817, title = {The life cycle and natural history of the tropical aphid Cerataphis fransseni (Homoptera: Aphididae: Hormaphidinae), with reference to the evolution of host alternation in aphids}, journal = {Journal of natural history}, volume = {29}, year = {1995}, pages = {231-242}, abstract = {

We describe the life cycle and general biology of the tropical cerataphidine aphid Cerataphis fransseni. We demonstrate that this aphid migrates between trees of Styrax benzoin and various species of palms; palm-feeding populations have previously been known as C. variabilis and C. palmae, which now become synonyms of C. fransseni. On S. benzoin the fundatrix induces a relatively simple gall which can contain \>6000 aphids at maturity with a large number of reproductively sterile soldiers that protect the gall from predators. These galls are apparently produced throughout the year. Colonies on the secondary host plants, palms, are apparently obligately tended by ants whereas colonies within galls on Styrax are never tended by ants. We discuss the life cycle of this tropical aphid with respect to hypotheses for the evolution and maintenance of host alternation.

}, doi = {10.1080/00222939500770101}, url = {http://www.tandfonline.com/doi/abs/10.1080/00222939500770101$\#$.VKrUcHt79iZ}, author = {DL Stern and S Aoki and D U Kurosu} }