水稻叶绿素合成缺陷突变体cbd1的鉴定及其功能基因的图位克隆与分析
发布时间：2019-06-19 20:07
【摘要】：高光合效率是水稻高产的主要决定因素之一。叶绿素是植物光合作用中的主要色素,其含量的高低不仅能呈现出叶片颜色的深浅变化,同时也与植株的光合效率息息相关。通过水稻叶色突变体来挖掘叶绿素合成的基因并探讨基因的作用机制,对于解析水稻高光合效率的成因具有重要的生物学意义,也为后续生产上超级稻的培育奠定良好的理论基础。在本研究中,我们鉴定了一个叶绿素合成缺陷突变体cbd1(cbd:chlorophyll biosynthesis deficiency),其叶绿素和类胡萝卜素的含量均显著下降至野生型的2/3左右,表现为全生育期淡绿叶表型。对野生型和突变体进行同步温度梯度处理后发现,随着温度的下降,两者叶绿素含量呈现相同程度的下降,这说明cbd1对温度不敏感。透射电镜观察结果表明,cbd1幼叶中叶绿体的形态和类囊体的结构均保持完整,与野生型无明显差别。同样的,cbd1的株高、分蘖数、穗长、剑叶长、剑叶宽、粒重等农艺性状均较野生型没有变化。然而,有意思的是cbd1的每穗粒数却显著增加。遗传分析结果表明,cbd1中的淡绿叶表型受一对隐性核基因控制。利用图位克隆的方法我们将基因限定在第10染色体上,分子标记D5和RM25669之间物理距离为57.45Kb,其间含有10个预测的基因。序列比对分析后发现,在OsHemA基因(Os10g0502400)的ATG上游约1.1Kb的启动子区含有一个433bp的mPing短末端重复类转座子的插入,导致该基因的表达量和相应的编码蛋白含量均显著下调。OsHemA基因编码谷氨酸-tRNA还原酶(GluTR),催化叶绿素和血红素合成的起始步骤,即将谷氨酸-tRNA还原为谷氨酰-tRNA-1-半醛。在cbd1中过表达OsHemA基因不仅能够恢复叶片的表型,同时将叶绿素和类胡萝卜的含量提高至野生型相当水平,这说明OsHemA基因下调表达是导致cbd1色素含量下降的原因。HemA基因最先在大肠杆菌中被发现,在藻类、蕨类、苔藓类和高等植物中都普遍存在。在绝大多数禾本科作物中,HemA基因多以家族的形式存在,然而在水稻中仅有一个同源基因存在。OsHemA基因在不同的组织中均有表达,尤其在叶片、叶鞘等绿色组织中表达量丰富。与野生型相比,cbd1突变体中OsHemA基因的表达量则呈现不同程度地下调,与之相应的,叶绿体合成途径中的其他基因也随之下降,这证实了 GluTR是一个关键的限速酶。GluTR蛋白含有保守的N-端结构域和C-端结构域,前者参与tRNA和NADP的结合,后者促进同源二聚体的形成。在水稻原生质体瞬时转化体系中,HemA-GFP融合蛋白主要定位在叶绿体中,而GFP-HemA则在叶绿体和细胞质中均有定位。综合以上结果证实:OsHemA基因是水稻中唯一的HemA同源基因,其编码的蛋白作用于叶绿体上,对催化叶绿素合成的起始至关重要。
[Abstract]:High photosynthetic efficiency is one of the main factors determining the high yield of rice. Chlorophyll is the main pigment in plant photosynthesis, and its content can not only show the change of leaf color, but also closely related to the photosynthetic efficiency of plants. It is of great biological significance to excavate the genes of chlorophyll synthesis and explore the mechanism of genes through rice leaf color mutants, which is of great biological significance for the analysis of the causes of high photosynthetic efficiency in rice, and also lays a good theoretical foundation for the cultivation of super rice in subsequent production. In this study, we identified a chlorophyll synthesis deficient mutant cbd1 (cbd:chlorophyll biosynthesis deficiency),) whose chlorophyll and carotenoid contents decreased significantly to about 2 鈮，
本文编号：2502604
[Abstract]:High photosynthetic efficiency is one of the main factors determining the high yield of rice. Chlorophyll is the main pigment in plant photosynthesis, and its content can not only show the change of leaf color, but also closely related to the photosynthetic efficiency of plants. It is of great biological significance to excavate the genes of chlorophyll synthesis and explore the mechanism of genes through rice leaf color mutants, which is of great biological significance for the analysis of the causes of high photosynthetic efficiency in rice, and also lays a good theoretical foundation for the cultivation of super rice in subsequent production. In this study, we identified a chlorophyll synthesis deficient mutant cbd1 (cbd:chlorophyll biosynthesis deficiency),) whose chlorophyll and carotenoid contents decreased significantly to about 2 鈮，
本文编号：2502604
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