Molecular Basis of Gametophytic Self-Incompatibility in Nicotiana and Petunia

本课题旨在研究雌蕊S蛋白在配子体自交不亲和中的功能及其对S基因表达的调控。利用烟草和矮牵牛，高博士将1)通过测试将新的S基因导入不同S等位基因的纯合植物或将反义S基因导入同一S等位基因的纯合子植物对自交不亲和行为的影响，建立直接的证据，证明S蛋白对自交不亲和反应负责；2)利用在转基因植物中表达的嵌合蛋白鉴定S蛋白的S等位基因专一性结构域：3)检测S蛋白保守的半胱氨酸残基突变对其功能的影响；4)通过将S基因的5‘上游序列与报告基因GUS融合，然后通过顺序缺失来检测其对转基因植物中GUS表达的影响，从而确定控制组织特异性和发育调控的S基因表达的序列；5)利用一个独特的自交亲和花柱部分突变体，鉴定与S基因的花柱活性部分相关的蛋白质。这些实验的结果将提供关于自交不亲和的分子基础的重要信息。许多高等植物有一种机制，称为自交不亲和性，可以防止来自给定植物的花粉使同一植物的雌性组织(雌蕊)自交受精。控制这种自交不亲和性的基因已经确定，但不亲和性发生的机制尚不清楚。除了植物生物学家固有的兴趣之外，对这一过程的理解在农业上也有明显的应用。

The proposed project is to study the functional aspects of pistil S-proteins and regulation of S-gene expression in gametophytic self-incompatibility. Using Nicotiana alata and Petunia inflata, Dr. Kao will 1) establish direct evidence that S-proteins are responsible for the self-incompatibility reaction by testing the effect on self-incompatibility behavior of introducing either a new S-gene into plants homozygous for a different S-allele, or an antisense S-gene into plants homozygous for the same S-allele; 2) identify the s-allele specificity domain of the S-protein by using chimeric S-proteins expressed in transgenic plants; 3) test the effect of mutating the conserved cysteine residues of S- proteins on their function; 4) determine the sequences controlling tissue specific and developmentally regulated expression of S-genes by fusing their 5' upstream sequences to a reporter gene, GUS, and then using sequential deletion to test the effect on expression of GUS in transgenic plants; 5) identify a protein associated with the style activity part of the S-locus using a unique self-compatible style-part mutant of N. alata. The result of these experiment will yield important information on the molecular basis of self-incompatibility. %%% Many higher plants have a mechanism, termed self-incompatibility, with prevents the pollen from a given plant from self fertilizing the female tissue (pistil) of the same plant. Genes controlling this self- incompatibility have been identified but the mechanism whereby the incompatibility occurs is unknown. In addition to its inherent interest to plant biologists, there are clear applications to agriculture to an understanding of this process.