A transgenic self-incompatible Arabidopsis thaliana model for evolutionary and mechanistic studies of crucifer self-incompatibility.

Molecular genetic studies of self-incompatibility (SI) can be difficult to perform in non-model self-incompatible species. Recently, an Arabidopsis thaliana transgenic model was developed for analysis of the SI system that operates in the Brassicaceae by inter-species transfer of genes encoding the S-locus receptor kinase (SRK) and its ligand, the S-locus cysteine-rich (SCR) protein, which are the determinants of SI specificity in the stigma and pollen, respectively. This article reviews the various ways in which the many advantages of A. thaliana and the extensive tools and resources available in this model species have allowed the use of transgenic self-incompatible SRK-SCR plants to address long-standing issues related to the mechanism and evolution of SI in the Brassicaceae. It also presents the unexpected results of a candidate gene approach aimed at determining if genes related to genes previously reported to be involved in the SI response of Brassica and genes required for disease resistance, which exhibits many similarities to the SI response, are required for SI in A. thaliana. These various studies have provided a novel insight into the basis of specificity in the SRK-SCR interaction, the nature of the signalling cascade that culminates in the inhibition of 'self' pollen, and the physiological and morphological changes that are associated with transitions between the outbreeding and inbreeding modes of mating in the Brassicaceae.