9300047 Kirk Volvox carteri is a potentially powerful model system for analysis of the genetics of differentiation and development. It is a eukaryotic multicellular organism but it contains only two cell types, mortal somatic cells and immortal germ cells, which are arranged in a predictable pattern within a simple spheroid. The organism is normally haploid, reproduction is usually asexual and mutations are phenotypically obvious but because sexual reproduction is readily induced, formal genetic analysis is possible. Mutations which cause organizational abnormalities are viable because cell development is autonomous. Because there are close relatives of Volvox that lack cellular differentiation, the potential for evolutionary studies exists. One limitation of this organism as a model system has been the lack of a genetic map and an inability to transform it. The latter procedure has been recently developed in our laboratory and we are embarking upon the former. The genetic map has been expanded by the incorporation of many restriction-fragment-length-polymorphism (RFLP) and drug resistance markers. Methods for tagging and recovering genes of interest via transposon mutagenesis have been developed. The goals for the next five years are to tag, identify and map genes that regulate development and differentiation of germ and somatic cells as well as morphogenetic movements and cellular senescence and programmed cell death. %%% The achievement of the goals of this project will provide a bridge organism between simpler single cell organisms and much more complex multicellular organisms for the study and understanding of development and differentiation as well as evolution.
