Functional genomics approach toward identification of pollen-part factor of self-incompatibility in the rosaceous fruit trees.

花粉雌蕊自交不亲和（self-incompatibility, Sl）中的相互作用是开花植物缺乏免疫系统的一种自我识别机制。本研究的目的是澄清Sl的分子基础。Sl的遗传解释是一个单一的S位点与多个等位基因。然而，最近的研究结果表明，雌蕊和花粉的Sl反应分别由雌蕊- s和花粉- s基因这两个紧密相连的基因控制。在茄科、蔷薇科和玄参科三个科中，雌蕊- s基因的产物是一种核糖核酸酶S-RNase。花粉s基因的身份一直是未知的，是该研究领域的中心问题。本研究对蔷薇属杏树（Prunus dulcis）的s座区进行了广泛的鉴定，以确定花粉s基因。通过对S-locus区域的克隆和测序，鉴定出一个具有单倍型特异性多态性的花粉表达F-box蛋白基因。该基因以s -单倍型特异性F-box蛋白基因命名为SFB。SFB的位置近S-RNase基因，等位基因之间的序列多样性高，以及花粉特异性表达模式等特点表明，它是基于S-RNase的Sl系统中花粉-s基因的第一候选。F-box蛋白被认为是SCF复合物的一个组成部分，SCF复合物是E3泛素连接酶的一类。新的F-box蛋白基因作为花粉s基因的首个候选基因的发现表明，蛋白降解的泛素/蛋白酶体途径在自交不亲和性反应中起着核心作用。

Pollen-pistil interaction in self-incompatibility (Sl) represents a self-recognition mechanism of flowering plants that lack immune system. The goal of this research is to clarifying the molecular basis of Sl. Sl has been genetically explained by a single S locus with multiple alleles. However, recent findings indicate that Sl reaction of pistil and pollen are controlled by tightly linked different genes, pistil-S and pollen-S genes, respectively. In the three families, Solanaceae, Rosaceae and Scrophulariaceae, the pistil-S gene product is a ribonuclease, S-RNase. Identity of pollen-S gene has long been unknown, and the central issue of this research area.In this study, the S-locus region of a rosaceous fruit tree almond (Prunus dulcis) was extensively characterized to identify pollen-S gene. Through cloning and sequencing of a the S-locus region, a novel pollen-expressed F-box protein gene with haplotype-specific polymorphism was identified. The gene was named SFB for S-haplotype specific F-box protein gene. The characteristics of SFB, proximal location to the S-RNase gene, high level of sequence diversity among alleles, and pollen-specific expression pattern, suggest that it is the first candidate for the pollen-S gene of the S-RNase-based Sl system. The F-box protein is known as a component of SCF complex, a class of E3 ubiquitin ligase. The finding of a new F-box protein gene as the first candidate of pollen-S gene implicates that ubiquitin/proteasome pathway of protein degradation plays a central role in self-incompatibility reaction.