GENETICS OF THE SELF-INCOMPATIBILITY (S-) LOCI

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Currently, we are focusing on empirical side of self-incompatibility (S-) locus evolution. Self-incompatibility (SI) is a genetic mechanism to prevent inbreeding in plants. S-locus determines mating specificities (who can mate with whom), and analogous to sex chromosome in human. Additionally, S-locus experiences evolutionary forces similar to MHC loci because both SI MHC are mechanisms of self-/nonself-recognition. 2007-2008 With Mike Hickerson(CUNY Queens) : We aim to develop statistically rigorous computational tools to test phylogeographic hypotheses. Abstract: Fundamental questions about the determinants and dynamics of community assembly and the historically geographic nature of species diversity have been vexing the scientific community since before the times of Darwin. By estimating the geographic history of all species within a community, phylogeographic data may be able to address the controversial and unresolved hypotheses explaining the forces determining community assembly. Toward this goal, we are expanding hierarchical approximate Bayesian computation (hABC) models used in msBayes (a program which we released to test phylogeographic hypotheses such as simultaneous divergence of species pairs). 2007-2008: With graduate student: Takashi Miyake, We are characterizing the diversification pattern of self-incompatibility locus at the molecular level in poppy. Abstract: Self-incompatibility is a genetic system of self-recognition that allows flowering plants to avoid self-fertilization. Self-incompatible plants are typically fertilized only by pollen with a different mating specificity (S-locus genotype), producing strong diversifying selection. Dozens of alleles may be maintained in a single population, and polymorphism within species is ancient. However, empirical knowledge of the evolutionary dynamics of self-incompatibility loci presently comes from just two systems, the RNase-based system in Solanaceae, Scrophulariaceae and Rosaceae, and the SRK system of Brassicaceae. We propose to characterize self-incompatibility in the Papaveraceae, which has a different molecular mechanism of self-incompatibility, by examining sequence diversity of S-alleles in five species of Papaveraceae from four genera. Diversifying selection creates and maintains extreme levels of genetic variation in terms of the numbers of alleles, their sequence divergence, and the age of polymorphism. Diversifying selection underlies many important processes in nature including self-recognition systems and disease resistance loci such as the human MHC loci. This study will reconstruct the history of diversification of a self-recognition gene that has not been previously examined, and will provide the first comparison of self-incompatibility loci in which the selective process is the same (gametophytic), but the molecular basis differs.