矮秆小粒水稻潇湘矮的形态学与分子遗传学分析

【目的】研究揭示潇湘矮矮秆小粒的遗传机制,为潇湘矮的育种利用提供理论基础。【方法】利用水稻育种过程中自然突变而得到的稳定遗传的矮秆小粒水稻材料潇湘矮,对其进行农艺性状考查、赤霉素(GA_3)和油菜素内酯(BR)敏感性分析、遗传学分析,并利用潇湘矮与其近等基因系NIL(NIP)衍生的F_2群体对控制矮秆小粒的基因xxa进行图位克隆,最终利用转基因互补试验验证候选基因。【结果】潇湘矮除表现为矮秆小粒外,其穗长变短,穗型紧凑,千粒重极显著下降。不同浓度梯度的赤霉素(GA_3)和油菜素内酯(BR)处理,发现潇湘矮对GA_3部分敏感,而对BR不敏感。遗传分析发现其符合孟德尔3∶1分离规律。图位克隆将xxa基因定位于第5染色体In Del标记F81和F82之间约70 kb区间的物理距离内。该区间包含8个开放阅读框(ORF)。其中,第5个ORF(LOC_Os05g26890)被注释为水稻株高基因D1。序列分析发现,潇湘矮的D1基因在第5和12外显子分别有1个碱基的无义替换和3个碱基的缺失,其中第12外显子3个碱基的缺失导致1个赖氨酸的缺失。转基因互补显示D1可以恢复潇湘矮的表型。【结论】潇湘矮控制株高的途径可能与GA_3代谢有关;潇湘矮矮秆小粒表型符合单隐性核基因控制的遗传规律;潇湘矮矮秆小粒性状是由D1基因突变所致。

Morphological and Molecular Genetic Analysis of a Dwarf and Small Grain Rice Variety Xiaoxiang’ai

【Objective】To uncover the genetic mechanism of a dwarf and small grain variety Xiaoxiang’ai (XXA), and lay an important theoretical foundation in rice dwarfing breeding.【Method】Rice variety XXA characterized as a dwarf and small grain phenotype was derived from natural mutation under breeding process. The agronomic traits of XXA were investigated. Its sensibility to phytohormone was analyzed under GA3 and BR treatments at various concentrations. Genetic analysis of XXA with different varieties and fine mapping of xxa gene from the F2 population derived from the cross between near-isogenic lines NIL(NIP) and XXA were done. Furthermore, complementary assay was performed to confirm the candidate gene.【Result】The XXA shows short spikes and compact panicles, with significant decrease in 1000-grain weight under GA3 and BR treatments, we found that XXA is partially sensitive to GA3, whereas insensitive to BR. The segregation behavior in each of the derived F2 populations between XXA and either varieties was consistent with the Mendelian monogenic ratio of 3∶1. The xxa gene was finally narrowed down to a 70 kb physical region between the InDel markers F81 and F82 on chromosome 5. Within this region, eight open reading frames (ORFs) were predicted, of which, ORF5 (LOC_Os05g26890) has been annotated as a Dwarf1 gene (D1). Furthermore, sequence analysis of all the region revealed that there are only two mutation sites including one 1-bp nonsense mutation in the 5th exon and a 3-bp deletion that resulted in a lysine deletion in the 12th exon of D1. The complementary assay showed that the abnormal phenotype of XXA can be recovered.【Conclusion】The dwarf and small grain phenotype is probably associated with GA3 metabolism. The abnormal phenotype is mainly controlled by a single recessive gene. The D1 indisputably corresponds to mutation phenotype of XXA.