McClure B A, Haring V, Ebert P R, Anderson M A, Simpson R J, Sakiyama F, Clarke A E
Plant Cell Biology Research Centre School of Botany, University of Melbourne, Parkville, Victoria, Australia.
Nature. 1989;342(6252):955-7. doi: 10.1038/342955a0.
Self-incompatibility in flowering plants is often controlled by a single nuclear gene (the S-gene) having several alleles. This gene prevents fertilization by self-pollen or by pollen bearing either of the two S-alleles expressed in the style. Sequence analysis shows that three alleles of the S gene of Nicotiana alata encode style glycoproteins with regions of defined homology. Two of the homologous regions also show precise homology with ribonucleases T2 (ref. 4) and Rh (ref. 5). We report here that glycoproteins corresponding to the S1, S2, S3, S6 and S7 alleles isolated from style extracts of N. alata are ribonucleases. These style S-gene-encoded glycoproteins account for most of the ribonuclease activity recovered from style extracts. The ribonuclease specific activity of style extracts of the self-incompatible species N. alata is 100-1,000-fold higher than that of the related self-compatible species N. tabacum. These observations implicate ribonuclease activity in the mechanism of gametophytic self-incompatibility.
开花植物中的自交不亲和性通常由具有多个等位基因的单个核基因（S基因）控制。该基因可阻止自身花粉或携带花柱中表达的两个S等位基因之一的花粉受精。序列分析表明，烟草的S基因的三个等位基因编码具有特定同源区域的花柱糖蛋白。其中两个同源区域还与核糖核酸酶T2（参考文献4）和Rh（参考文献5）显示出精确的同源性。我们在此报告，从烟草花柱提取物中分离出的与S1、S2、S3、S6和S7等位基因相对应的糖蛋白是核糖核酸酶。这些由花柱S基因编码的糖蛋白占从花柱提取物中回收的核糖核酸酶活性的大部分。自交不亲和物种烟草的花柱提取物的核糖核酸酶比活性比相关的自交亲和物种烟草高100 - 1000倍。这些观察结果表明核糖核酸酶活性参与了配子体自交不亲和的机制。
