04-P012 Germ line specification in the milkweed bug, Oncopeltus fasciatus (Hemiptera)

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MECHANISMS OF DEVELOPMENT

1 2 6 (2 0 0 9) S1 0 7–S 11 2

suggest NaB has differential affects on exocrine and endocrine

issue, we are studying germ line development in a non-model

pancreas development.

insect, Oncopeltus fasciatus (Hemiptera), a species for which RNAi-based functional studies are well established. Hemipteran

doi:10.1016/j.mod.2009.06.195

oocytes are first patterned within ovaries of a markedly different anatomy than those of many Holometabolous insects (including Drosophilla melanogaster), making O. fasciatus a fascinating com-

04-P011 Oocyte patterning in non-model insects: Creating transcriptomes of the ovaries and embryos of two insect species using 454 sequencing Ben Ewen-Campen, Frederike Alwes, Mary Wahl, Cassandra Extavour Harvard University, Cambridge, MA, United States

parative system in which to investigate such early specification events as germ cell formation. Here, we present preliminary data regarding the expression patterns of several conserved germ line specification factors in O. fasciatus, including vasa, nanos, pumilio, and aubergine. In addition, we outline our approach to studying the function of these genes in germ cells, as well as our attempts to elucidate

The body axes of many animals are initially patterned by the

the mechanisms that localize these factors to germ cells. By com-

asymmetric distribution of maternal mRNAs and proteins in the

paring our results with the handful of heavily studied organisms

oocyte. In Drosophila, these maternal factors are synthesized by

for which functional data are available, we hope to gain insight

the 15 nurse cells that connect to each oocyte within the ovary.

into the evolution of the developmental pathways involved in

However, insect ovaries fall into three anatomical categories, of

germ cell formation and function.

which Drosophila represents only one. The telotrophic meroistic ovaries of the true bugs (Hemiptera), for example, possess a single

doi:10.1016/j.mod.2009.06.197

group of syncytial nurse cells that connect to all oocytes simultaneously via extended nutritive tubes. The panoistic ovaries of basal insects including crickets (Orthoptera) do not possess nurse cells. Little is known about the production or localization of

04-P013

maternal factors within the developing oocytes of insects pos-

A temporal modulation of FGF, Wnt, BMP and Retinoic Acid sig-

sessing these different ovary types.

nalling is required for neural crest induction

To address this issue, we have begun to characterize the ovarian and embryonic transcriptomes of a Hemipteran (the milk-

Benjamin Steventon, Roberto Mayor University College London, London, United Kingdom

weed bug, Oncopeltus fasciatus) and an Orthopteran (the cricket Gryllus bimaculatus) using 454 pyrosequencing. Both of these species have rich histories as laboratory species, and both possess large ovaries that facilitate live imaging and microinjection. Our sequence data will allow us to identify orthologs of candidate genes involved in a variety of embryonic patterning processes, and will lay the groundwork for future studies on the development and evolution of insect body plans. Additionally, these sequences will augment the relatively few genomic resources available for hemimetabolous insects, thereby contributing to our understanding of genomic evolution during the 330 million years since the divergence of Hemimetabola and Holometabola from their last common ancestor. doi:10.1016/j.mod.2009.06.196

During embryonic development, a series of inductive interactions is thought to explain a gradual increase in structural complexity. Although the molecular signals involved in the induction of many cell types has been established, the combinatorial and temporal requirement of inductive signals is not known. The neural crest is an embryonic stem cell population, whose induction has been shown to be dependent of at least four different signalling pathways: BMPs, Wnts, FGFs and Retinoic Acid signalling. However, whether these signals work at the same time or in a sequencial manner remains to be analysed. By asking when each signal is required for the induction of the neural crest, the temporal problem of induction is addressed. Firstly, specific assays to separate three distinct phases of the inductive process are established. Next, by using a combination of inducible constructs and soluble proteins or inhibitor the role of BMP, Wnt, FGF and Retinoic Acid signalling in each step is analysed. In

04-P012

the first phase, FGF signals are required along with the inhibi-

Germ line specification in the milkweed bug, Oncopeltus fasciatus

tion of Wnt signals. Subsequently continued FGF signalling

(Hemiptera)

together with high Wnt and intermediate BMP signalling is

Ben Ewen-Campen, Cassandra Extavour

required. Finally, activation of all four pathways is required for continued maintenance of the neural crest. This work brings

Harvard University, Cambridge, MA, United States

together previous work in the field and provides a single conserved model for neural crest induction. In addition, a mecha-

Despite the diversity of mechanisms used by animals to spec-

nism of induction is proposed in which the sequence, duration

ify their germ line during embryogenesis, germ cells across Met-

and level of signalling activity is important in achieving a spe-

azoa share the expression of several conserved genes. The

cific response.

conservation of these markers has provided a powerful means for identifying germ cells in a wide variety of non-model organisms, but surprisingly little is known about the molecular functions of these markers in different animals. To address this

doi:10.1016/j.mod.2009.06.198