bims-plasge Biomed News
on Plastid genes
Issue of 2022‒03‒27
three papers selected by
Vera S. Bogdanova
Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences

  1. Int J Mol Sci. 2022 Mar 12. pii: 3064. [Epub ahead of print]23(6):
      In flowering plants, C-to-U RNA editing can be critical to normal functions of mitochondrion-encoded proteins. Mitochondrial C-to-U RNA editing is facilitated by many factors from diverse protein families, of which the pentatricopeptide repeat (PPR) proteins play an important role. Owing to their large number and frequent embryo lethality in mutants, functions of many PPRs remain unknown. In this study, we characterized a mitochondrion-localized DYW-type PPR protein, DEK48, functioning in the C-to-U RNA editing at multiple mitochondrial transcripts in maize. Null mutation of Dek48 severely arrests embryo and endosperm development, causing a defective kernel (dek) phenotype, named dek48. DEK48 loss of function abolishes the C-to-U editing at nad3-185, -215, and nad4-376, -977 sites and decreases the editing at 11 other sites, resulting in the alteration of the corresponding amino acids. Consequently, the absence of editing caused reduced assembly and activity of complex I in dek48. Interestingly, we identified a point mutation in dek48-3 causing a deletion of the Tryptophan (W) residue in the DYW motif that abolishes the editing function. In sum, this study reveals the function of DEK48 in the C-to-U editing in mitochondrial transcripts and seed development in maize, and it demonstrates a critical role of the W residue in the DYW triplet motif of DEK48 for the C-to-U editing function in vivo.
    Keywords:  PPR-DYW protein; RNA editing; complex I; mitochondria; seed development
  2. Int J Mol Sci. 2022 Mar 11. pii: 3035. [Epub ahead of print]23(6):
      Pentatricopeptide repeat (PPR) proteins are a large protein family in higher plants and play important roles during seed development. Most reported PPR proteins function in mitochondria. However, some PPR proteins localize to more than one organelle; functional characterization of these proteins remains limited in maize (Zea mays L.). Here, we cloned and analyzed the function of a P-subfamily PPR protein, PPR278. Loss-function of PPR278 led to a lower germination rate and other defects at the seedling stage, as well as smaller kernels compared to the wild type. PPR278 was expressed in all investigated tissues. Furthermore, we determined that PPR278 is involved in the splicing of two mitochondrial transcripts (nad2 intron 4 and nad5 introns 1 and 4), as well as RNA editing of C-to-U sites in 10 mitochondrial transcripts. PPR278 localized to the nucleus, implying that it may function as a transcriptional regulator during seed development. Our data indicate that PPR278 is involved in maize seed development via intron splicing and RNA editing in mitochondria and has potential regulatory roles in the nucleus.
    Keywords:  C-to-U RNA editing; PPR protein; intron splicing; maize; seed development
  3. New Phytol. 2022 Mar 20.
      Most plant pentatricopeptide repeat (PPR) proteins localize and function inside plastids and mitochondria. However, the function of PPRs that only localize in the cytoplasm remains unknown. Here, we demonstrated that the rice (Oryza sativa) PPR protein CYTOPLASM-LOCALIZED PPR1 (OsCPPR1) contributes to pollen development and localizes in the cytoplasm. Knocking down OsCPPR1 transcript levels led to abnormal plastid development in tapetal cells, prolonged tapetal programmed cell death (PCD) and tapetum degradation, and significantly reduced pollen fertility. Transcriptome analysis revealed that the transcript level of OsGOLDEN-LIKE1 (OsGLK1), encoding a transcription factor that regulates plastid development and maintenance, was significantly higher in the OsCPPR1 knockdown plants compared to wild type. We further determined that OsCPPR1 downregulates OsGLK1 transcript levels by directly binding to the single-stranded regions of OsGLK1 mRNAs. Overexpression of OsGLK1 resulted in abnormal tapetum and plastid development, similar to that seen with OsCPPR1 knockdown plants, and suppression of OsGLK1 partially restored pollen fertility in the OsCPPR1 knockdown plants. Therefore, OsCPPR1 suppresses OsGLK1 in regulating plastid development and PCD in the tapetum. Our work revealed novel functions for a cytosolic PPR, demonstrating the diverse roles of PPRs in plants and identifying a new regulatory mechanism for regulating pollen development in rice.
    Keywords:  OsGLK1; PPR; cytoplasm-localized; post-tr; programmed cell death; tapetal plastid