| Photosynthesis of green plant is the major energy source for organisms on earth to survive and develop. Chloroplast is a very important organelle of plant cells. Besides photosynthesis, it also carries out other essential metabolism. The biogenesis of chloroplast from proplastid is the prerequisite of photosynthesis. The chloroplast development requires coordinated expression of the nuclear and the plastid genome. However, we still know little about this process. The analysis of albino or pale-green mutant is an important way to investigate chloroplast biogenesis.Chloroplast biogenesis is a complex process in higher plants, which needs the coordinated gene expression both the nuclear and the chloroplast genome. Due to the limit plastid genome capability, most genes controlling chloroplast biogenesis are in nuclear compartment. In this work, we screened a mutant atecb2, which showed albino cotyledons and seedling lethal. Microscopy observation shown that chloroplast contains no lamella, implying chloroplast development is arrested at the early stage. Genetic analysis indicated that the mutant phenotype was a single recessive locus and co-segregated with the T-DNA insertion site Complement test analysis demonstrated that AtECB2 is responsible for atecb2 mutant phenotype. AtECB2 gene encodes a PPR protein localized to chloroplast, which displays highly expression level in cotyledon and seedling. The atecb2 mutant displayed obvious different expression pattern on chloroplast-related genes in contrast to those of wild type. Immunblot analyses also indicated that the amount of photosynthetic protein was largely decreased in atecb2 mutant. PCR fragment sequence indicated that one published RNA editing events have not occurred in atecb2 mutant. Combined these data and our results indicates that AtECB2 is a specificity factor for accD transcripts RNA editing, and the defective accD RNA editing could lead to the block of early chloroplast biogenesis.
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