A triallelic system of S5 is a major regulator of the reproductive barrier and compatibility of indica-japonica hybrids in rice
A triallelic system of S5 is a major regulator of the reproductive barrier and compatibility of indica-japonica hybrids in rice
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DOI：
10.1073/pnas.0804761105
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发表时间：
2008-08-12
影响因子：
11.1
通讯作者：
Zhang, Qifa
中科院分区：
文献类型：
--
作者：
Chen, Jiongjiong;Ding, Jihua;Zhang, Qifa
杂种不育是合子后生殖隔离的主要形式。尽管几十年来生殖隔离一直是进化生物学中的一个关键问题，但直到最近才发现了少数生殖隔离基因。亚洲栽培水稻（Oryza sativa L.）分为籼稻和粳稻两个亚种。籼稻和粳稻的杂交品种通常是高度不育的。一组特殊的水稻种质，被称为宽亲和性品种，当与籼稻和粳稻杂交时，能够产生高度肥沃的杂种。本研究利用基于图谱的克隆方法克隆了籼粳杂交不育性和广泛亲和性的主要基因座S5。我们发现S5编码一种天冬氨酸蛋白酶调节胚囊的生育能力。籼稻（S5-i）和粳稻（S5-j）等位基因有两个核苷酸的差异。宽相容性基因（S5-n）在预测的S5蛋白的in端有一个大的缺失，导致该蛋白的亚细胞错定位，因此可能是无功能的。这一试验等位基因系统对栽培水稻的进化和人工育种具有深远的意义。由于S5-i和S5-j造成的生殖障碍，籼稻和粳稻之间的遗传分化可能会被强制执行，而物种一致性可能会通过广泛相容基因的基因流来维持。
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 IN 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.