Progress 11/15/04 to 11/14/07
Outputs
OUTPUTS: Polyphenisms including caste formation are key components of insect biology important to many species of agricultural importance. Goals of this study were to characterize how different genes are expressed during caste formation of the polyembryonic wasp Copidosoma floridanum. Results of the study have been disseminated primarily through the peer-reviewed literature via refereed publications. Outcomes have also been reported in a diversity of national and international meetings, seminars presented in US universities, and seminars presented at academic institutions in other countries.
PARTICIPANTS: Participants: Dr. David Donnell and Dr. Michael R. Strand, University of Georgia. The project provided postdoctoral training support for Dr. Donnell.
Impacts
Major outcomes of the study included development of expressed sequence tag (EST) libraries and identification of selected developmental genes identified through homology to other organisms. These tools were used to characterize stages of caste formation and to identify essential genes required for the caste formation process in C. floridanum.
Publications
- Donnell, D., Corley, L., Chen, G., and M. R. Strand. 2004. Inheritance of germ cells mediates caste formation in a polyembryonic wasp. Proc. Natl. Acad. Sci. USA 101, 10095-10100. Donnell, D. and M. R. Strand. 2006. Caste specific gene expression in the polyembryonic wasp Copidosoma floridanum. Insect Biochem. & Mol. Biol. 36, 141-153.
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Progress 11/15/05 to 11/14/06
Outputs
The overall goal of this study is to characterize the evolution of caste formation in polyembryonic insects. Progress this past year included comparative studies of caste formation in different species. Behavioral and developmental assays determined that sexual asymmetries exist in soldier caste development with females producing aggressive soldiers and males producing non-aggressive larvae. Molecular allozyme and msat markers for characterization of population structure of Copidosoma floridanum were also developed.
Impacts
The evolution of altruism formation of specialized castes is a widespread phenomenon in insects and other animals. This interdisciplinary study provides functional insights on this process. The study also provides a unique educationl opportunity for training young scientists in evolutionary, population and developmental biology.
Publications
- Giron, D., K. G. Ross, and M. R. Strand. 2007. The presence of soldier larvae determines the outcome of competition in a polyembryonic wasp. J. Evol. Biol. 20, 165-172.
- Keasar, T., M. Segoli, R. Barak, S. Steinberg, D. Giron, M. R. Strand, A. Bouskila, and A. R. Harari. 2006. Costs and consequences of superparasitism in the polyembryonic wasp Copidosoma koehleri. Ecol. Entomol. 31, 277-283.
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Progress 11/15/04 to 11/14/05
Outputs
This grant has the primary objectives of identifying differentially expressed genes in larval castes of the wasp Copidosoma floridanum, characterizing the expression patterns of these genes, and conducting loss-of-function experiments on a subset of the genes. To date, over 230 novel expressed sequences have been identified as the result of a bidirectional suppression subtractive hybridization (SSH) screen involving mRNA isolated from the two larval castes. An estimated 85% of these sequences are differentially expressed in one of the two castes. Genes encoding putative enzymes, proteinase inhibitors, odorant-binding and chemosensory proteins, cysteine-rich peptides and cuticular proteins have so far been identified in the isolated sequences. At present, in situ hybridization experiments with DIG-labeled probes have been conducted on a majority of the putative odorant-binding protein genes identified in the SSH experiments as well as a number of genes coding for
putative serine proteinases. The oligonucleotide primers used to prepare the DIG probes for the in situs described above are also being used for conducting the double-stranded RNA silencing experiments described in the grant. This work has just started, however, a precise time in the development of Copidosoma embryos for conducting the RNA silencing experiments has been established.
Impacts
Many of the genes identified in this study are novel to the study of caste formation. The discovery of a number of putative odorant-binding protein genes and cysteine-rich peptide sequences are expected to be of great significance to caste formation in Copidosoma given their potential role in facilitating the detection of the offspring of other wasps and the location of nutrient resources in the host.
Publications
- Donnell, D.M., Strand, M.R., 2006. Caste-based differences in gene expression in the polyembryonic wasp Copidosoma floridanum. Insect Biochemistry and Molecular Biology, in press.
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