College of Life and Environmental Sciences, Shanghai Normal University, Shanghai 200234, China.
J Integr Plant Biol. 2011 Apr;53(4):258-69. doi: 10.1111/j.1744-7909.2011.01030.x. Epub 2011 Mar 18.
AtECB2 encodes a pentatricopeptide repeat (PPR) protein that regulates the editing of the plastid genes accD and ndhF. The ecb2-1 knockout shows an albino phenotype and is seedling lethal. In this study, we isolated an allelic mutant of the AtECB2 gene, ecb2-2, which showed delayed greening phenotype but could complete their life cycle. In this mutant, the Thr(500) is converted to Ile(500) in the 13(th) PPR motif of the AtECB2 protein. Transmission electron microscopy demonstrated that chloroplast development was delayed in both the cotyledons and leaves of the mutant. An investigation of the chloroplast gene expression profile indicated that PEP (plastid-encoded RNA polymerase) activity in ecb2-2 cotyledons was not obviously affected, whereas it was severely impaired in ecb2-1. This result suggests that the PEP activities cause the different phenotypes of the ecb2-1 and ecb2-2 mutants. The editing efficiency of the three editing sites of accD (C794 and C1568) and ndhF (C290) in the mutant was dynamically altered, which was in agreement with the phenotype. This result indicates that the editing efficiency of accD and ndhF in the ecb2-2 mutant is associated with a delayed greening phenotype. As ecb2-2 can survive and set seeds, this mutant can be used for further investigation of RNA editing and chloroplast development in arabidopsis.
AtECB2 编码一个五肽重复（PPR）蛋白，该蛋白调节质体基因 accD 和 ndhF 的编辑。ecb2-1 敲除突变体表现出白化表型，且幼苗致死。在这项研究中，我们分离了 AtECB2 基因的一个等位突变体 ecb2-2，该突变体表现出变绿延迟表型，但能完成其生命周期。在这个突变体中，第 13 个 PPR 基序中的 Thr（500）被转换为 Ile（500）。透射电子显微镜显示突变体的子叶和叶片中叶绿体发育延迟。对质体基因表达谱的研究表明，ecb2-2 子叶中的 PEP（质体编码 RNA 聚合酶）活性没有明显受到影响，而在 ecb2-1 中则受到严重损害。这一结果表明，PEP 活性导致了 ecb2-1 和 ecb2-2 突变体的不同表型。accD（C794 和 C1568）和 ndhF（C290）三个编辑位点的编辑效率在突变体中动态改变，这与表型一致。这一结果表明，ecb2-2 突变体中 accD 和 ndhF 的编辑效率与变绿延迟表型有关。由于 ecb2-2 能够存活并结籽，因此该突变体可用于进一步研究拟南芥中的 RNA 编辑和叶绿体发育。
