Progress 11/01/02 to 10/31/05
Outputs
The long term goals of my research are to understand the genetic basis underlying morphological variation in animals. The specific objectives of this project were twofold:(1)to describe the cellular events underlying polyembryonic proliferation of C. floridanum and (2)to identify genes involved in polyembryonic proliferation of C. floridanum. To accomplish these objectives we conducted cell fate mapping experiments and we characterized the C. floridanum hedgehog gene during polyembryonic development. The fate mapping experiments indicate that most C. floridanum embryonic cells remain totipotent and proliferate during the first 10 days of development whereas there is a small subset of cells that undergoes differentiation and produces the soldier caste. The C. floridanum hedgehog transcript was found to be expressed in most embryonic cells but is absent from a small subset of cells. Based on these results, we suggest the hypothesis that the hedgehog pathway may be
involved in specifying the totipotent, proliferative embryonic cells and those cells not expressing hedgehog are fated to differentiate into soldier larvae during the first 10 days of development. Further functional testing of this hypothesis is necessary but these data do suggest that the hedgehog pathway is involved in stem cell fate. This is important new information because while the hedgehog pathway has been shown to be involved in some normal stem cell development, it is better known for its ability to change a normal cell into a cancerous cell that has unlimited proliferative capacity. Polyembryonic development in C. floridanum is an extreme example of cellular proliferation but it is not a disease state; rather, it is an adaptive trait that has significant fitness consequences for the wasp. Our results are an important first step in discovering the genetic mechanisms underlying polyembryonic development. We have completed the primary objectives for this project and this is the
final termination report.
Impacts
Despite the many genome projects that are contributing critical genetic information on a diversity of organisms, there is still very little understood about which genes are involved in specifying specific phenotypes. The polyembryonic wasp C. floridanum was used in this study as a model of normal, adaptive insect development that naturally mimics a proliferative stem cell system. Whereas most animals develop a single individual from a single egg, C. floridanum produces up to 3000 individuals from a single egg in two separate larval castes. The process of cellular proliferation and differentiation are responsible for this interesting developmental process and this project was an attempt to identify cellular events and genetic pathways responsible for the process of proliferation. We succeeded in characterizing cell fates during the first 10 days of development and we also showed correlated expression of the hedgehog gene with cell fates. This is important new
information on polyembryonic development and contributes to our understanding of stem cell fate specification. In addition, the results of this project bring a new understanding of the genetic mechanisms that are involved in polyembryony and provide hypotheses for future research.
Publications
- No publications reported this period
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Progress 01/01/04 to 12/31/04
Outputs
Our work on this project in 2004 resulted in one publication and a masters thesis. Michael White successfully cloned and characterized the expression pattern of the C. floridanum hedgehog gene and its relationship to polyembryonic proliferation. Our results suggest that polyembryonic proliferation in the parasitoid wasp may be controlled by a genetic pathway that is also used by stem cells in other animal systems -- the hedgehog signal transduction pathway. Our work is a first step in understanding the genetic basis for stem cell proliferation in an insect.
Impacts
The results of this study will provide us with important information on cellular proliferation during an adaptive period of stem cell growth in an insect.
Publications
- Corley, L.S., White, M.A. & Strand, M.R. 2005. Both endogenous and environmental factors affect embryo proliferation in the polyembryonic wasp Copidosoma floridanum. Evolution & Development 7:115-121.
- Corley, L.S. 2005. Microevolution and development: studies of the genetic basis of adaptive variation in insects. Evolution & Development 7:79-80.
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Progress 01/01/03 to 12/31/03
Outputs
We have cloned two genes in the hedgehog signal transduction cascade from C. floridanum using degenerate PCR. We are currently doing in situ and RT PCR analysis of the transcript in order to determine if hedgehog is involved in cellular proliferation during polyembryony. The hedgehog signal transduction cascade has been shown to be involved in cellular proliferation throughout the metazoa, thus it is our hypothesis that hedgehog may be involved in the deranged proliferative phase of polyembryony in our wasp. If the hedgehog pathway is not involved. We will nevertheless characterize the role of hedgehog in segment polarity during normal embryonic development of C. floridanum embryos. We are also using 3RACE and 5RACE to sequence the full length of one of the gene fragments that we have isolated. We have successfully used 3RACE to sequence part of one of the two genes.
Impacts
The results of this study will provide us with important information on cellular proliferation during an adaptive period of stem cell growth in an insect.
Publications
- No publications reported this period
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