Chen H, Zhao Z, Liu L, Kong W, Lin Y, You S, Bai W, Xiao Y, Zheng H, Jiang L, Li J, Zhou J, Tao D, Wan J
National Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing, China.
Food Crops Research Institute, Yunnan Academy of Agricultural Sciences, Kunming, China.
Heredity (Edinb). 2017 Sep;119(3):166-173. doi: 10.1038/hdy.2017.32. Epub 2017 Jun 28.
Oryza longistaminata originates from African wild rice and contains valuable traits conferring tolerance to biotic and abiotic stress. However, interspecific crosses between O. longistaminata and Oryza sativa cultivars are hindered by reproductive barriers. To dissect the mechanism of interspecific hybrid sterility, we developed a near-isogenic line (NIL) using indica variety RD23 as the recipient parent and O. longistaminata as the donor parent. Both pollen and embryo sac semi-sterility were observed in F hybrids between RD23 and NIL. Cytological analysis demonstrated that pollen abortion in F hybrids occurred at the early bi-nucleate stage due to a failure of the first mitosis in microspores. Partial embryo sacs in the F hybrids were defective during the functional megaspore formation stage. Most notably, nearly half of the male or female gametes were aborted in heterozygotes S40S40, regardless of their genotypes. Thus, S40 was indicated as a one-locus sporophytic sterility gene controlling both male and female fertility in hybrids between RD23 and O. longistaminata. A population of 16 802 plants derived from the hybrid RD23/NIL-S40 was developed to fine-map S40. Finally, the S40 locus was delimited to an 80-kb region on the short arm of chromosome 1 in terms with reference sequences of cv. 93-11. Eight open reading frames (ORFs) were localized in this region. On the basis of gene expression and genomic sequence analysis, ORF5 and ORF8 were identified as candidate genes for the S40 locus. These results are helpful in cloning the S40 gene and marker-assisted transferring of the corresponding neutral allele in rice breeding programs.
长雄蕊野生稻起源于非洲野生稻，具有赋予对生物和非生物胁迫耐受性的宝贵性状。然而，长雄蕊野生稻与栽培稻品种之间的种间杂交受到生殖障碍的阻碍。为了解析种间杂种不育的机制，我们以籼稻品种RD23为受体亲本、长雄蕊野生稻为供体亲本，构建了一个近等基因系（NIL）。在RD23与NIL的F杂种中观察到花粉和胚囊半不育。细胞学分析表明，F杂种中的花粉败育发生在双核早期，原因是小孢子的第一次有丝分裂失败。F杂种中的部分胚囊在功能大孢子形成阶段存在缺陷。最值得注意的是，无论基因型如何，杂合子S40S40中近一半的雄配子或雌配子败育。因此，S40被认为是一个控制RD23与长雄蕊野生稻杂种中雄性和雌性育性的单基因座孢子体不育基因。利用RD23/NIL-S40杂种构建了一个由16802株植物组成的群体，用于精细定位S40。最终，根据93-11品种的参考序列，将S40基因座定位到第1染色体短臂上一个80 kb的区域。该区域定位了8个开放阅读框（ORF）。基于基因表达和基因组序列分析，确定ORF5和ORF8为S40基因座的候选基因。这些结果有助于在水稻育种计划中克隆S40基因并进行相应中性等位基因的分子标记辅助转移。
