小麦叶绿体蛋白质编码基因RNA编辑位点的测定及与返白现象的关系

RNA Editing Sites in Chloroplast Protein-coding Genes in Leaf White Mutant of Triticum aestivum

RNA编辑是一种转录后基因加工修饰现象,广泛存在于高等植物细胞器中。已有研究表明,RNA编辑与植物发生白化或者黄化有关。通过PCR、RT-PCR及测序的方法,对具有阶段性白化特性的小麦(Triticum aestivum)返白系FA85及其野生型矮变一号(Aibian 1)的叶绿体蛋白质编码基因RNA编辑位点进行了测定,在14个基因上发现了26个编辑位点。有5个编辑位点在2个株系之间存在编辑效率的差异,且这些差异的位点均位于编码叶绿体RNA聚合酶的基因上,其中3个位点编辑前后对应的蛋白质二级结构可能有差异。对2个株系叶绿体中PEP、NEP及PEP、NEP共同依赖基因转录水平的检测显示,除psbA和clpP外,其它基因在小麦返白系中的转录水平均有不同程度的下降。这种转录水平的显著下降及叶绿体RNA聚合酶基因上RNA编辑位点编辑效率的改变,可能与小麦返白系叶片的返白有关。

RNA editing is a post-transcriptional process and mainly occurs in higher plant organelles. Lacking RNA editing in some plants can cause albino or yellow leaves. We investigated RNA editing in 14 protein-coding genes from the chloroplast genome of Triticum aestivum Aibian 1 and the wheat leaf-stage albino mutant FA85. We found 26 editing sites in these genes. The two plants significantly differed in editing efficiency of 5 partial editing events. The 5 sites include the phosphoenylpyruvate （PEP） genes rpoC2, rpoA and rpoB, and 3 of them are predicted to change the secondary protein structure. We further analyzed the transcriptional pattern of chloroplast genes that depend on PEP, on nuclear export protein （NEP） and on both PEP and NEP. The mRNA levels of chloroplast genes, except for psbA and clpP, were lower in the mutant than wild-type leaves. The wheat leaf-stage albino phenotype may be attributed to a decrease in efficiency of the 5 editing sites and alteration of transcript level of some chloroplast genes.