Sassa H, Hirano H, Ikehashi H
Faculty of Horticulture, Chiba University, Japan.
Mol Gen Genet. 1993 Oct;241(1-2):17-25. doi: 10.1007/BF00280196.
Japanese pear (Pyrus serotina Rehd.) exhibits gametophytic self-incompatibility. Following our previous findings that basic ribonucleases in the styles of Japanese pear are associated with self-incompatibility genes (S-RNases), stylar proteins with high pI values were analyzed by two-dimensional gel electrophoresis further to characterize S-RNases. A group of basic proteins of about 30 kDa associated with self-incompatibility genes were identified. These proteins contained sugar chains which reacted with concanavalin A and wheat germ agglutinin, and thus were designated as S-glycoproteins of Japanese pear. The fact that the S-glycoprotein was expressed at a much lower level in a self-compatible mutant than in the original variety suggested a role of S-glycoproteins in mediating self-incompatibility of Japanese pear. Immunoblot analysis indicated that S-glycoproteins are identical to previously identified S-RNases. The S-glycoproteins were predominantly expressed in the style, in the ovary in trace amounts, and not in leaf, pollen or germinated pollen. The N-terminal amino acid sequences of the S-glycoproteins showed homology not only with each other but also with those of the S-allele-associated proteins from plants of the family Solanaceae at levels of about 30-50%.
日本梨（Pyrus serotina Rehd.）表现出配子体自交不亲和性。基于我们之前的研究发现，即日本梨花柱中的碱性核糖核酸酶与自交不亲和基因（S - 核糖核酸酶）相关，我们进一步通过二维凝胶电泳分析了高pI值的花柱蛋白，以表征S - 核糖核酸酶。鉴定出了一组与自交不亲和基因相关的约30 kDa的碱性蛋白。这些蛋白含有能与伴刀豆球蛋白A和麦胚凝集素反应的糖链，因此被命名为日本梨的S - 糖蛋白。在自交亲和突变体中，S - 糖蛋白的表达水平远低于原始品种，这一事实表明S - 糖蛋白在介导日本梨的自交不亲和性中发挥作用。免疫印迹分析表明，S - 糖蛋白与先前鉴定的S - 核糖核酸酶相同。S - 糖蛋白主要在花柱中表达，在子房中有微量表达，而在叶片、花粉或萌发花粉中不表达。S - 糖蛋白的N端氨基酸序列不仅彼此之间具有同源性，而且与茄科植物中S等位基因相关蛋白的同源性约为30 - 50%。
