小麦叶绿素缺失突变体Mt135的叶绿体基因差异表达分析

Differential Expression of Chloroplast Genes in Chlorophyll-Deficient Wheat Mutant Mt135 Derived from Space Mutagenesis

小麦叶绿素缺失突变体Mt135自交后代稳定表现绿株、条纹株和白化株3种类型,其中条纹株白色组织和白化株的叶绿体数目和结构发生突变,完全失去光合能力。为研究该突变体叶绿体基因表达与光合作用的关系,采用实时荧光定量PCR技术,分析了白化株和条纹株的叶绿体基因表达。在白化株中共检测到40个差异表达基因,涉及4类功能(编码光反应相关蛋白、编码叶绿体内能量代谢相关酶、核糖体合成和tRNA合成),包括18个上调表达和22个下调表达基因;在条纹株中共检测到13个上调表达基因,其表达变化趋势与在白化株中一致。白化株的差异表达基因中,编码光系统II、I结构蛋白的psb、psa和ycf等基因家族的基因表达量显著下调;多个编码核糖体蛋白大、小亚基的基因表达量改变,尤其是核糖体蛋白小亚基编码基因rps14和23SrRNA的编码基因23SrDNA表达量显著下调。推测Mt135突变性状与参与光反应相关蛋白的编码基因、叶绿体内能量代谢相关酶的编码基因、核糖体合成相关基因以及tRNA合成相关基因表达量的改变密切相关。

The leaf color of chlorophyll-deficient mutant Mt135 （Triticum aestivum L.） shows albino, striped, and green pheno- types. The number and structure of chloroplasts in the albino plant and albino tissue of striped plants are significantly different from those in the wild type, which results in the complete loss of photosynthetic function in albino plant/tissue. The expression alteration of chloroplast genes in young seedlings of albino Mt135 and wild type was studied using RT-PCR technique, and 40 genes were identified to be differentially expressed in the albino plant/tissue, including 18 genes up-regulated and 22 genes down-regulated. These genes categorized into four groups encoded proteins responding photoreaction （31%）, enzymes of energy metabolism in chloroplast （27%）, ribosome biogenesis （25%）, and tRNA biosynthesis （17%）. The alteration trends of 13 up-regulated genes detected in the striped plants were similar to those in albino seedlings. Among these differentially expressed genes, gene families of psb, psa, and ycf encoding structural proteins of photosystem II and I were down-regulated significantly, genes encoding ribosomal protein subunits were altered, especially expressions of gene rps14 encoding small ribosomel subunit protein and 23S rDNA encoding 23S rRNA were down-regulated significantly. It was concluded that the differential expression of these genes related with proteins responding photoreaction, enzymes of energy metabolism in chloroplast, ribosome biogenesis and tRNA biosynthesis may induce the phenotype of mutant Mt135.