摘要
植物类病变与早衰的发生受激素、代谢、环境信号等多重因素影响,其分子机制尚未完全清楚.从水稻辐射诱变库中筛选到一个类病变早衰突变体lmes6(lesion mimic and early senescence 6),与野生型相比,lmes6突变体叶片从分蘖期开始出现类病变、叶色发黄、叶绿素含量显著降低,其穗长、每穗粒数、粒长及单株产量显著降低;组织染色显示该突变体的叶片出现细胞程序性死亡及活性氧过量积累;且该突变体增强了对水稻白叶枯病与细菌性条斑病的抗性.遗传分析表明lmes6的突变表型受单隐性核基因控制.利用图位克隆技术将目的基因精细定位在水稻7号染色体53 kb区间内,经候选基因预测与PCR测序分析,发现在lmes6突变体中一个编码Fd-GOGAT1(依赖于铁氧还蛋白的谷氨酸合酶)的基因LOC_Os07g46460发生了一个碱基替换,导致苯丙氨酸(F)变为亮氨酸(L),是该基因的一个新的复等位基因,与其他已报道的lc7、abc1、spl32等位突变相比,lmes6对水稻的生长发育、产量等方面抑制较小.对Fd-GOGAT1进行系统发育树分析及同源蛋自序列比对,结果表明Fd-GOGAT1蛋白在单子叶植物中高度保守.
Abstract
The occurrence of lesion mimic and early senescence is affected by multiple factors,including hormones,metabolism,and ambient signals.However,the molecular mechanism underlying this process remains incompletely understood.In this study,we identified a lesion mimic and early senescence mutant,named lmes6(lesion mimic and early senescence 6),through screening of a heavy ion beam radiation mutagenesis library.Comparative analysis with the wild-type control revealed that the leaves of the lmes6 mutant exhibited lesion mimic,chlorosis,and a significant reduction in chlorophyll content from the tillering stage.Addi-tionally,the mutant displayed a notable decrease in panicle length,grain number per panicle,grain length,and yield per plant.Tissue staining showed that the mutant exhibited programmed cell death and excessive accumulation of reactive oxygen species in the leaves.Furthermore,the mutant displayed enhanced resistance to bacterial blight and bacterial leaf streak.Genetic analysis showed that the mutant phenotype was governed by a single recessive nuclear gene.Through map-based cloning techniques,the gene was precisely mapped to a 53 kb region on rice chromosome 7.Candidate gene prediction and PCR sequencing analysis identified a gene,LOC_Os07g46460,which encodes Fd-GOGATl(ferredoxin-dependent glutamate synthase 1)in the lmes6 mutant.A single base substitution in this gene resulted in the conversion of L-phenylalanine(F)to leucine(L),which is one of new multiple alleles of this gene.Interestingly,compared to the three allelic mutations of this gene reported,lc7,abcl,and spl32,the lmes6 mutant exhibited less impact on growth and yield of rice.Phylogenetic analysis and alignment of the homologous protein sequences of Fd-GOGAT1 revealed its high conservation among monocots.
维普
万方数据