水稻是世界上最早驯化的重要粮食作物之一。水稻芒可以保护水稻种子不被鸟琢食,是水稻重要的驯化性状之一。芒在野生稻中普遍存在,对野生稻的生存和传播至关重要,然而在驯化和人工选择过程中该性状逐渐被淘汰。定位和克隆水稻长芒相关基因是研究水稻芒驯化遗传机制的基础。本研究以籼稻恢复系东南恢810为受体、漳浦野生稻为供体构建的146个染色体片段置换系(chromosome segment substitution lines, CSSLs)为研究材料,调查了146个CSSLs株系和双亲的芒长,结果表明在4个置换系中检测到1个控制水稻芒长主效基因GAD1-2,位于水稻第8号染色体;利用重叠代换作图法,将GAD1-2定位在Ind8-10和RM4936标记之间,遗传距离约为4.75 Mb。选择分离群体中的显性单株,利用开发的标记,最终将GAD1-2 基因定位在两个 Indel 标记之间,两者间的物理距离约为27 kb,该区域内只有两个候选基因Os08g0485500和Os08g0485400。经测序和分析表明,Os08g0485500是GAD1-2的候选基因,GAD1-2在保守的ORF区域存在6个碱基缺失,导致丝氨酸和半胱氨酸这两个氨基酸缺失,从而表现长芒的性状;在Os08g0485500基因位点已克隆了1个控制水稻芒长的GAD1基因,推测GAD1-2与GAD1为等位基因。本研究为进一步理解水稻起源演化和水稻芒长发育基因的遗传机制奠定了基础。

Rice is an important food crop in the world. The awn may protect rice seeds from being cut by birds, which is important in rice domestication, survival and diffusion. However, the characteristic of awn is gradually washed out during rice domestication and artificial selection. Mapping and cloning of rice awn genes is the basis of studying the genetic mechanism of awn domestication. In this study, 146 chromosome segment substitution lines (CSSLs) derived from DongNanHui 810/ZhangPu wild rice with DongNanHui 810 as the recurrent parent were used to analyze the quantitative trait loci (QTL) controlling the long awn of rice. The results showed that four CSSLs contained one QTL for the long awn. Using substitution mapping, the GAD1-2 gene was mapped between two markers (Ind8-10 and RM4936) on chromosome 8, with a genetic distance of about 4.75 Mb. Using the dominant individuals of segregating populations, the GAD1-2 gene was eventually located between two Indel markers, with a physical distance of about 27 kb, which contained only two candidate genes Os08g0485500 and Os08g0485400. Sequencing analysis showed that Os08g0485500 was the candidate gene of GAD1-2. Further analysis showed that there were six bases missing in the conservative ORF region, resulting in the absence of serine and cysteine that led to the long awn of the four CSSLs. The GAD1 gene was also cloned in this position, suggesting that GAD1-2 and GAD1 were allelic. This study laid a foundation for further understanding of the genetic regulation mechanism and genetic evolution of the awn gene in rice.