水稻ygl80黄绿叶突变体的遗传分析与目标基因精细定位

通过化学诱变获得遗传稳定的水稻黄绿叶突变体ygl80。与野生型亲本10079相比,ygl80突变体在苗期和孕穗期叶片叶绿素分别下降76.64%和54.59%,类胡萝卜素含量分别下降53.85%和41.18%,成熟期株高、每株有效穗数、每穗着粒数、穗长和千粒重分别减少14.8%、16.5%、21.3%、9.1%和7.4%。遗传分析表明,ygl80的突变性状由1对隐性核基因控制。利用(ygl80/浙辐802)F2作为定位群体,将突变基因定位在第5染色体长臂InDel标记C2和C3之间,遗传距离分别为0.24 cM和0.39 cM,两标记之间的物理距离约为90 kb,此区间内包含11个预测基因。基因组序列分析发现,ygl80突变体在编码叶绿素合酶的YGL1(LOC_Os05g28200)基因编码区第5027碱基处(位于第14外显子),碱基C突变为碱基T,使编码蛋白序列第348位的脯氨酸(Pro)突变成亮氨酸(Leu)。该基因是已报道的水稻ygl1黄绿叶突变基因的等位基因。ygl80突变体在整个生育期都表现为黄绿叶,而ygl1突变体在苗期叶片黄化,中期慢慢转绿,后期叶色以及总叶绿素和类胡萝卜素的含量接近野生型,这可能是YGL1基因编码的叶绿素合酶蛋白的氨基酸不同突变位点造成的。

Genetic Analysis and Gene Fine Mapping of Yellow-Green Leaf Mutant ygl80 in Rice

A yellow-green leaf mutant ygl80 was isolated by chemical mutagenesis. Compared with the wild-type parent 10079, chlorophyll content of the ygl80 mutantdecreased by 76.64% and 54.59%, and the carotenoid content decreased by 53.85% and 41.18% at the seedling and booting stages, respectively. In addition, plant height, number of productive panicles per plant, number of spikelets per panicle, panicle length and 1000-grain weight reduced by 14.8%, 16.5%, 21.3%, 9.1%, and 7.4%, respectively, at the maturity. Genetic analysis showed that the yellow-green leaf trait of the ygl80 mutant was controlled by one pair of recessive nuclear genes. Genetic mapping of the mutant gene was conducted by using 627 yellow-green leaf individuals from the F₂ mapping population of ygl80/Zhefu802. Finally, the mutant gene was mapped between InDel markers C2 and C3 on the long arm of chromosome 5, with genetic distances of 0.24 cM and 0.39 cM, respectively, and with physical distance of 90 kb, in this region eleven predicted genes had been annotated. Sequencing analysis of these candidate genes between the mutant and its wild-type parent revealed a single base change (C5027T) of YGL1 (LOC_Os05g28200) gene for chlorophyll synthase resulted in a missense mutation (P348L) in the encoded product, suggesting that the ygl80 mutant gene is allelic to the ygl1 gene. The ygl80 mutant exhibited yellow-green trait throughout the growing period. But the ygl1 mutant showed yellow-green trait at seedling stage, then turned into green slowly, and its leaf color and chlorophyll and carotenoid contents almost closed to those of the wild-type parent during the later stage of growth. Different phenotypes of the two mutants may be caused by different mutational sites of genomic sequenceof YGL1 gene encoding chlorophyll synthase.