The Role of the S-Locus F-Box Gene in S-RNase-Based Self-Incompatibility

Self-incompatibility (SI) allows pistils of flowering plants to reject self-pollen to prevent inbreeding, and to accept non-self pollen to promote outcrossing. How the pistil distinguishes between self- and non-self pollen, and how the pistil rejects self-pollen have been under intensive investigation for many decades. Petunia inflata, a wild relative of garden petunia, will be used as a model to address these questions in one type of the SI mechanism. Here, the S-RNase gene expressed in the pistil, and the PiSLF (P. inflata S-locus F-box) gene expressed in the pollen determine the outcome of pollination. In this project, molecular genetic and biochemical approaches will be used to study the biochemical properties of PiSLF, and to determine how one allelic variant of PiSLF interacts differently with its self and non-self S-RNases to result in specific growth inhibition of self-pollen tubes. The results will advance understanding of the long-standing questions about the mechanism of SI, as well as of self/non-self discrimination mechanisms in other biological systems. Since many F-box proteins are involved in mediating protein degradation, this work will also contribute to understanding cellular and developmental processes in other organisms in which F-box proteins are involved. SI has potential commercial applications in hybrid seed production, an important agricultural practice for producing plants of higher vigor and higher yield. Understanding the SI mechanism could make it feasible to restore the SI trait back to crop species to facilitate hybrid seed production. If this can be accomplished, it will have tremendous agronomic benefits. This project will be entirely carried out by graduate and undergraduate students, providing them training in plant reproductive biology and experience in the design and execution of experiments that will be valuable for their future research careers.