The Function Of AtECB2, A PPR Protein In Chloroplast Of Arabidopsis

The AtECB2is a previous reported PPR protein, which is targeted inchloroplast and belongs to the DYW subgroup. We have previouslyshown that AtECB2functions in RNA editing of accD and ndhF inArabidopsis thaliana, and RNA editing is a post-transcriptional processthat converts C to U in organelle mRNAs. Here, we prepared thepolyclonal antibody specific for the protein, and demonstrated thatAtECB2directly binds to the three targets in vivo by the RNAimmunoprecipitation (RIP) assay with the specific antibody againstAtECB2. We successful induced the expression the PPR motif of AtECB2in vitro. RARE1is another PPR protein, which is involved in RNA editing ofaccD, yeast two-hybrid experiments showed that the DYW domain ofAtECB2had no interaction with RARE in yeast. In addition, we analyzedatecb2-2which has a point mutate in the13th PPR motif of the AtECB2protein. We found that the true leaves of atecb2-2had a delayedgreening phenotype, and TEM results showed that the early true leavesof atecb2-2were defective in chloroplast development and graduallyrecovered to a normal level with its growth. Northern blot showed thatthe rbcL transcripts almost restored in consistent with the delayedgreening phenotype. However, the PEP (plastid-encoded RNApolymerase) activity was not totally recovered, which indicated themutation of AtECB2also impact the PEP activity, besides its influence inRNA editing, thus block the development of chloroplast.