長久以來,，雜交育種被用于改善農(nóng)作物,，但是當(dāng)兩種亞洲主要水稻品種雜交時,，經(jīng)常產(chǎn)生一種更強(qiáng)壯但是不育的雜交品種,。張啟發(fā)及其同事發(fā)現(xiàn)了一種此前未知的基因——他們將其命名為S5——造成了秈稻和粳稻這兩種主要水稻品系的雜交品種不育。兩種稍有不同的S5基因——秈稻和粳稻各有一種——導(dǎo)致水稻健康而可育,，但是當(dāng)來自這兩種水稻的這種基因通過雜交培育結(jié)合到一起之后,，它們的后代是高度不育的。相關(guān)論文發(fā)表在美國《國家科學(xué)院院刊》（PNAS）上,。
這組科學(xué)家還研究了另一種具有“廣親和性”的水稻品系,，結(jié)果發(fā)現(xiàn)它的S5基因的一大段序列丟失是廣親和性水稻與其他兩種水稻雜交時能產(chǎn)生可育品種的原因。他們對另外16種亞洲水稻品種進(jìn)行了取樣,，證實(shí)了S5基因的角色,，首次為大多數(shù)秈-粳雜交稻為何不育提供了直接的原因證據(jù)。這組作者提出,，他們的結(jié)果可以幫助改善水稻培育,，并為全世界提供更優(yōu)良的水稻作物。（生物谷Bioon.com）
生物谷推薦原始出處：
PNAS,，doi: 10.1073/pnas.0804761105，Jiongjiong Chen,，Qifa Zhang
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.
