Comparative and Evolutionary Genomics of Self-Incompatibility in the Brassicaceae

Cornell Univ - State: Awds Made Prior May 2010, Ithaca NY

Investigators

Abstract

0077289 Nasrallah Plants employ elaborate and sophisticated signaling systems that allow them to assess genetic relatedness among pollen donors. In many species of the mustard family (the Brassicaceae), a cell-cell signaling system based on the activity of receptor and ligand proteins displayed at the surfaces of the stigma epidermis and pollen grains respectively, results in the arrest of self-related pollen at the stigma surface. This self-incompatibility system, which is controlled by a large number of variants at the S locus, prevents self-fertilization and inbreeding, and promotes cross-pollination and outbreeding. The family Brassicaceae is comprised almost equally of self-fertilizing and outcrossing species, with self-incompatibility being the major determinant of this polymorphism in mating system control. As such, the presence or absence of a functional self-incompatibility system determines the patterns of genetic variation in populations and influences the rate and mode of evolutionary change in this family. The S loci of self-incompatible and self-fertile species belonging to diverged subgroupings of the Brassicaceae will be analyzed. In addition, transgenic experiments as well as interspecific hybrids and backcross populations between self-incompatible and self-fertile Arabidopsis species will be used to determine which genes are required to effect changes in mating system. These studies will be facilitated by advances in comparative genomics, namely the availability of the Arabidopsis nuclear genome sequence, the feasibility of constructing large-insert genomic libraries, and the rapid generation of molecular markers and maps. It is anticipated that the lineage of genes that play a major role in enforcing outcrossing will be traced, promising to shed light on the long-standing questions relating to the origin of SI in flowering plants and the genetic mechanisms underlying transitions between outcrossing and self-fertilizing mating systems.