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

Abstract

The leaf color of chlorophyll-deficient mutant Mt135 (Triticum aestivum L.) shows albino, striped, and green phenotypes. 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.