Biochemical Basis of S-RNase-Based Self-Incompatibility

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Most flowering plants produce complete flowers, with anthers and pistil located in close proximity. This arrangement is conducive to self-pollination, which leads to inbreeding and consequent reduced fitness in progeny. Many flowering plants have adopted self-incompatibility (SI) to circumvent the tendency for inbreeding. This genetic trait allows the pistil to reject self-pollen but accept non-self pollen for fertilization. The PI is using Petunia inflata as a model to study SI, with the ultimate goal of understanding how the pistil can distinguish self and non-self pollen, and how this recognition leads to specific rejection of self-pollen. His group previously identified the S-RNase gene as responsible for the pistil's ability to recognize and reject self-pollen. The PI's group, along with Dr. Seiji Takayama's group in Japan, found that pollen employs multiple S-locus F-box (SLF) genes in its SI function. In this project, the PI will use molecular approaches to test the collaborative non-self-recognition model that explains how multiple SLF proteins interact with a single S-RNase to allow non-self pollen tubes, but not self pollen tubes, to escape its toxic effect. The results obtained will lead to a better understanding of the interactions between these proteins that underlie this important inbreeding-preventing mechanism. This proposed research has wider implications for the self/non-self recognition process, a fundamental process in biology, as well as for studying protein degradation, a key regulatory mechanism in many biological processes. The SLF and S-RNase genes could be used to facilitate hybrid-seed production, and if accomplished, this will have tremendous agronomic benefits. The PI will engage four graduate and five to six undergraduate students in this project to prepare them for future careers in research, and will continue to participate in an annual biology fair at Penn State to educate the public, particularly K-12, about plant reproductive biology and SI.