苹果叶绿素合成关键酶基因MdHEMA1生物信息学和表达分析

Bioinformatics and Expression Analysis of MdHEMA1 Encoding the Key Enzyme for Chlorophyll Biosynthesis in Apple

HEMA1编码谷氨酰-tRNA还原酶(Glu TR)的合成,是叶绿素生物合成的关键酶基因。本研究利用RACE技术从苹果叶片中克隆Glu TR的编码基因,将其命名为MdHEMA1。生物信息学分析表明:MdHEMA1基因位于苹果8号染色体上,其CDS长1638 bp,编码545个氨基酸残基,蛋白分子量为59279.4 Da,等电点为8.45。蛋白序列及结构分析显示该蛋白包含保守的谷氨酰-tRNA还原酶的N端结构域、莽草酸/奎尼酸脱氢酶结构域及谷氨酰-tRNA还原酶二聚结构域。进化树分析显示MdHEMA1蛋白与白梨(Pyrus×bretschneideri)Pb HEMA1亲缘关系最近。qRT-PCR结果显示,MdHEMA1在根、茎、叶、花、果实各组织器官中均有表达,但光合组织(茎、叶、果实)中的表达水平较高;该基因在叶片和果实不同发育期表达存在差异,表达量与叶片和果实内叶绿素含量变化趋势一致;而且干旱胁迫能够诱导该基因表达。启动子分析显示MdHEMA1基因启动子区域含有多种非生物胁迫相关的顺式作用元件。

Glu TR encoded by HEMA1 is the key enzyme in regulating chlorophyll biosynthesis. In this study,the encoding gene was cloned from apple leaves by RACE technology and designated as MdHEMA1. Bioinformatics analysis revealed that MdHEMA1 located on chromosome 8 of apple genome,with a CDS length of 1638 bp and encoded 545 amino acid residues. The calculated molecular mass was 59279. 4 Da with an isoelectric point of8. 45. Sequence analysis showed that MdHEMA1 protein contained 3 conserved domains. MdHEMA1 possessed the closest phylogenetic relationship with Pb HEMA1 from Pyrus × bretschneideri. qRT-PCR results revealed that MdHEMA1 exhibited a high expression level in photosynthetic tissues compared with that in other tissues. Besides,the expression level of MdHEMA1 varied in leaves and fruits at different developmental stages,which was positively correlated with the level of chlorophyll accumulation. The gene expression could also be induced by drought stress. Promoter analysis revealed that MdHEMA1 promoter possessed multiple putative cis-acting elements involved in abiotic stress.