MSP1 encodes an essential RNA-binding pentatricopeptide repeat factor required for nad1 maturation and complex I biogenesis in Arabidopsis mitochondria

New Phytol. 2023 Jun;238(6):2375-2392. doi: 10.1111/nph.18880. Epub 2023 Apr 17.


Mitochondrial biogenesis relies on nuclearly encoded factors, which regulate the expression of the organellar-encoded genes. Pentatricopeptide repeat (PPR) proteins constitute a major gene family in angiosperms that are pivotal in many aspects of mitochondrial (mt)RNA metabolism (e.g. trimming, splicing, or stability). Here, we report the analysis of MITOCHONDRIA STABILITY/PROCESSING PPR FACTOR1 (MSP1, At4g20090), a canonical PPR protein that is necessary for mitochondrial functions and embryo development. Loss-of-function allele of MSP1 leads to seed abortion. Here, we employed an embryo-rescue method for the molecular characterization of msp1 mutants. Our analyses reveal that msp1 embryogenesis fails to proceed beyond the heart/torpedo stage as a consequence of a nad1 pre-RNA processing defect, resulting in the loss of respiratory complex I activity. Functional complementation confirmed that msp1 phenotypes result from a disruption of the MSP1 gene. In Arabidopsis, the maturation of nad1 involves the processing of three RNA fragments, nad1.1, nad1.2, and nad1.3. Based on biochemical analyses and mtRNA profiles of wild-type and msp1 plants, we concluded that MSP1 facilitates the generation of the 3' terminus of nad1.1 transcript, a prerequisite for nad1 exons a-b splicing. Our data substantiate the importance of mtRNA metabolism for the biogenesis of the respiratory system during early plant life.

Keywords: 3′-end processing; Arabidopsis; MITOCHONDRIA STABILITY/PROCESSING PPR FACTOR1 (MSP1); RNA metabolism; group II introns; mitochondria; pentatricopeptide (PPR) proteins; splicing.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis Proteins* / metabolism
  • Arabidopsis* / metabolism
  • Electron Transport Complex I / genetics
  • Electron Transport Complex I / metabolism
  • Gene Expression Regulation, Plant
  • Introns / genetics
  • Mitochondria / metabolism
  • Mitochondrial Proteins / genetics
  • Mitochondrial Proteins / metabolism
  • Plant Proteins / metabolism
  • RNA / metabolism
  • RNA Splicing / genetics
  • RNA, Mitochondrial / metabolism


  • Arabidopsis Proteins
  • Electron Transport Complex I
  • Mitochondrial Proteins
  • Nad1 protein, Arabidopsis
  • Plant Proteins
  • RNA
  • RNA, Mitochondrial
  • AT5G66070 protein, Arabidopsis