摘要
In plants, RNA editing is a post-transcriptional process that changes specific cytidine to uridine in both mitochondria and plastids. Most pentatricopeptide repeat（PPR） proteins are involved in organelle RNA editing by recognizing specific RNA sequences. We here report the functional characterization of a PPR protein from the DYW subclass, Baili Xi（BLX）, which contains five PPR motifs and a DYW domain. BLX is essential for early seed development, as plants lacking the BLX gene was embryo lethal and the endosperm failed to initiate cellularization. BLX was highly expressed in the embryo and endosperm, and the BLX protein was specifically localized in mitochondria, which is essential for BLX function. We found that BLX was required for the efficient editing of 36 editing sites in mitochondria. Moreover, BLX was involved in the splicing regulation of the fourth intron of nad1 and the first intron of nad2. The loss of BLX function impaired the mitochondrial function and increased the reactive oxygen species（ROS） level. Genetic complementation with truncated variants of BLX revealed that, in addition to the DYW domain, only the fifth PPR motif was essential for BLX function. The upstream sequences of the BLX-targeted editing sites are not conserved, suggesting that BLX serves as a novel and major mitochondrial editing factor（MEF） via a new non-RNA-interacting manner. This finding provides new insights into how a DYW-type PPR protein with fewer PPR motifs regulates RNA editing in plants.
In plants, RNA editing is a post-transcriptional process that changes specific cytidine to uridine in both mitochondria and plastids. Most pentatricopeptide repeat（PPR） proteins are involved in organelle RNA editing by recognizing specific RNA sequences. We here report the functional characterization of a PPR protein from the DYW subclass, Baili Xi（BLX）, which contains five PPR motifs and a DYW domain. BLX is essential for early seed development, as plants lacking the BLX gene was embryo lethal and the endosperm failed to initiate cellularization. BLX was highly expressed in the embryo and endosperm, and the BLX protein was specifically localized in mitochondria, which is essential for BLX function. We found that BLX was required for the efficient editing of 36 editing sites in mitochondria. Moreover, BLX was involved in the splicing regulation of the fourth intron of nad1 and the first intron of nad2. The loss of BLX function impaired the mitochondrial function and increased the reactive oxygen species（ROS） level. Genetic complementation with truncated variants of BLX revealed that, in addition to the DYW domain, only the fifth PPR motif was essential for BLX function. The upstream sequences of the BLX-targeted editing sites are not conserved, suggesting that BLX serves as a novel and major mitochondrial editing factor（MEF） via a new non-RNA-interacting manner. This finding provides new insights into how a DYW-type PPR protein with fewer PPR motifs regulates RNA editing in plants.
基金
supported by the National Natural Science Foundation of China(Nos.31620103903 and 31621001)
partially by the 111 project
supported by the Peking-Tsinghua Joint Center for Life Sciences
