The evolution of genetic systems

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Our lab studies the evolution of modifiers of the mating system, and more generally, genes that bias their own transmission. We propose to conduct studies of the evolution and loss of self-incompatibility (SI) in the plant genus Leavenworthia.   This research will investigate mating system evolution from the level of the population on down to the gene sequence, and will focus on variation at the S-locus. Considerable progress has been made in the past 10 years by researchers who have cloned and sequenced this locus in the related genus Arabidopsis. We will capitalize upon this knowledge to extend the study of evolution and loss of SI to a plant group whose ecology has been well characterized.  We have already made significant progress on a number of components of this project, starting with the use of PCR primers that target a number of conserved regions of the S-locus as the means to clone and sequence the gene.  Our goals include: (1) confirmation that amplified products correspond to the S-locus; (2) development and testing of new and existing theory for allele genealogy and the dynamics of mutations at the S-locus that lead to self-compatibility; (3) examination of the effect of population size variation on mate availability and fecundity in SI populations; (4) tests for a selective sweep at the S-locus in self-compatible populations of Leavenworthia species; (5) using ancient S-locus polymorphism data to assist in reconstruction of the evolutionary history of the mating system in Leavenworthia species; (6) tests for the sheltering from selection of deleterious mutations in the S-locus region.  Collectively, this research will extend our understanding of the evolution of self-fertilization in plants.  Also proposed is the completion of a project to investigate the early stages of transposable element (TE) sequence evolution accompanying the "invasion" of a new genome by a heterologous TE (TE from another species) into experimental populations of yeast.  The two projects are conceptually related in that both are concerned with the evolution of genes that have the ability to bias their own transmission, a topic that our lab has explored for more than 20 years.