如何克服秈稻和粳稻雜種育性下降,、結(jié)實(shí)率很低問題,，是水稻育種家們幾十年來苦苦求索的。中國科學(xué)院院士,、華中農(nóng)業(yè)大學(xué)教授張啟發(fā)領(lǐng)銜的研究團(tuán)隊(duì)最近在這一領(lǐng)域取得重大進(jìn)展,，發(fā)現(xiàn)并成功分離克隆一個(gè)控制水稻秈粳雜種育性和廣親和性狀的主效基因，命名為S5,。該研究成果在水稻品種改良中具有重大應(yīng)用前景,。
研究人員稱，驢馬雜交產(chǎn)下子代（騾）,，而子代不具有正常生育能力,。這種生殖隔離現(xiàn)象在植物中同樣存在，如水稻秈粳亞種間雜種的不育性,。但科學(xué)家們還發(fā)現(xiàn),，在水稻中存在一類特殊的種質(zhì)資源稱為廣親和品種，或偏于秈稻,，或偏于粳稻,，它們與秈稻和粳稻雜交的后代都表現(xiàn)正?？捎?。
張啟發(fā)院士介紹說，栽培稻的秈粳不育和廣親和性的并存,，在生物進(jìn)化中是一種很奇特的現(xiàn)象：秈粳分化造就了豐富多樣的稻種資源,，也導(dǎo)致生殖隔離，而廣親和基因的存在則給秈粳亞種間基因交流提供橋梁,，與秈稻或粳稻雜交都不影響雜種育性,，對(duì)稻種的整體性有保障作用。他表示,，有效地應(yīng)用廣親和基因能夠克服水稻秈粳亞種間雜種的不育性,，從而利用秈粳亞種間強(qiáng)大的雜種優(yōu)勢(shì)提高水稻的產(chǎn)量。
廣親和基因因其重大的應(yīng)用價(jià)值,，在國內(nèi)外水稻界被認(rèn)為是一個(gè)非常重要的基因,，早在我國啟動(dòng)863計(jì)劃時(shí)，就列入了該基因分離克隆的研究內(nèi)容,。
張啟發(fā)課題組從1990年就開始了該基因的研究,，從遺傳分析、基因定位到最終克隆出S5基因,，歷時(shí)18年,，共有7家研究機(jī)構(gòu)的20多位研究人員參與項(xiàng)目研究,。該基因的成功克隆是我國科學(xué)家團(tuán)結(jié)合作的結(jié)晶，8月12日的《美國科學(xué)院院刊》以封面文章形式發(fā)表了該研究團(tuán)隊(duì)的研究論文,。（生物谷Bioon.com）
生物谷推薦原始出處：
PNAS August 12, 2008 vol. 105 no. 32 doi: 10.1073/pnas.0804761105
A triallelic system of S5 is a major regulator of the reproductive barrier and compatibility of indica–japonica hybrids in rice
Jiongjiong Chen*,, Jihua Ding*,, Yidan Ouyang*,, Hongyi Du*, Jiangyi Yang*, Ke Cheng*, Jie Zhao, Shuqing Qiu*, Xuelian Zhang?, Jialing Yao*, Kede Liu*, Lei Wang*, Caiguo Xu*, Xianghua Li*, Yongbiao Xue§, Mian Xia, Qing Ji‖, Jufei Lu‖, Mingliang Xu**, and Qifa Zhang*,
Abstract
Hybrid sterility is a major form of postzygotic reproductive isolation. Although reproductive isolation has been a key issue in evolutionary biology for many decades in a wide range of organisms, only very recently a few genes for reproductive isolation were identified. The Asian cultivated rice (Oryza sativa L.) is divided into two subspecies, indica and japonica. Hybrids between indica and japonica varieties are usually highly sterile. A special group of rice germplasm, referred to as wide-compatibility varieties, is able to produce highly fertile hybrids when crossed to both indica and japonica. In this study, we cloned S5, a major locus for indica–japonica hybrid sterility and wide compatibility, using a map-based cloning approach. We show that S5 encodes an aspartic protease conditioning embryo-sac fertility. The indica (S5-i) and japonica (S5-j) alleles differ by two nucleotides. The wide compatibility gene (S5-n) has a large deletion in the N terminus of the predicted S5 protein, causing subcellular mislocalization of the protein, and thus is presumably nonfunctional. This triallelic system has a profound implication in the evolution and artificial breeding of cultivated rice. Genetic differentiation between indica and japonica would have been enforced because of the reproductive barrier caused by S5-i and S5-j, and species coherence would have been maintained by gene flow enabled by the wide compatibility gene.
