Biochemical Basis of S-RNase-Based Self-Incompatibility

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PI: Teh-hui Kao Proposal Number: IOS-0843195Title of Proposal: Biochemical Basis of S-RNase-Based Self-IncompatibilityMost flowering plants produce bisexual flowers containing both male and female reproductive organs, and they would have a strong tendency to self-fertilize, if no mechanisms prevent them from doing so. Since inbreeding is deleterious to any organism, flowering plants have evolved a variety of reproductive strategies, including self-incompatibility (SI), to prevent inbreeding and promote out-crossing. SI allows pistils to reject self-pollen and accept non-self pollen for fertilization. This project uses Petunia inflata to study one type of SI mechanism, and has previously identified the S-RNase expressed by the pistil and PiSLF (P. inflata S-locus F-box) that is expressed by the pollen. During growth of a pollen tube in a pistil, the PiSLF in the pollen tube only allows self S-RNase to inhibit pollen tube growth. Several hypotheses that explain how PiSLF and S-RNase interact to elicit specific rejection of self pollen tubes will be tested. The project will use in vivo approaches to test these hypotheses by dissecting the functions of three domains of PiSLF in interactions with S-RNase, studying the biochemical function of a potential component of the PiSLF-containing complex, and examining the role of glycosylation of S-RNase in SI. SI provides a model for studying self/non-self recognition, so completion of this project will have wider implications for biological sciences. PiSLF and S-RNase could be used for restoring SI to crop species to facilitate hybrid seed production, which will have tremendous agronomic benefits. The project will engage three graduate and three undergraduate students to prepare them for future careers in research. The researchers in this project will continue to participate in an annual biology fair at Penn State to educate the attendees, particularly K-12, about plant reproductive biology and SI.