Biochemical and cellular and control of S-RNase-based self-incompatibility in flowering plants
Jiangbo Fan, Wei Liu, Qun Li, Yu’e Zhang, Yongbiao Xue*

State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences and National Center for Plant Gene Research, Beijing 100101.
*Corresponding Author：Tel: (+8610) 6255 2880; Fax: (+8610) 6253 7814; Email: ybxue@genetics.ac.cn

Abstract
Self-incompatibility (SI) is an intra-specific reproductive barrier to prevent self-fertilization and to promote cross-fertilization found in flowering plants. In the SI response, self or genetically related pollen is rejected by the pistil and non-self (cross) pollen accepted for fertilization. These outcomes are referred to as self-pollen incompatibility (SPI) and cross-pollen compatibility (CPC), respectively. Genetic studies show that a single polymorphic S-locus, encoding at least two components from both the pollen and pistil sides, controls the discrimination of self and cross pollen. Recent studies have revealed that plants use several distinct molecular mechanisms to accomplish the SI response. Among them, the Solanaceae, Plantaginaceae and Rosaceae appear to share a similar molecular mechanism. In these families, the SI specificity is determined by a ribonuclease protein (S-RNase) expressed in the pistil and a cluster of S-Locus F-box protein (SLF/SFB) in pollen. It is widely accepted that S-RNases are secreted by the pistil and taken up by growing pollen tubes and function as cytotoxins to arrest self-pollen tube growth. However, the biochemical and cellular mechanisms remain largely unclear. In this talk, I will present our recent data showing where and how S-RNase and SLF interact with each other to control CPC and SPI responses in Petunia hybrid, a solanaceous species.

Key Words: self-incompatibility; S-RNase; SLF; Petunia hybrida