Journal
PLANT JOURNAL
Volume 95, Issue 5, Pages 919-932Publisher
WILEY
DOI: 10.1111/tpj.14030
Keywords
maize; empty pericarp8; PPR; mitochondrion; complex I; seed development
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Funding
- National Key Research and Development Program of China [2016YFD0101003]
- National Natural Science Foundation of China [91735301, 31630053, 31500199]
- Shandong postdoctoral innovation fund [201501012]
- Fundamental Research Funds of Shandong University [2015HW010]
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Splicing of plant organellar group II introns is under accurate nuclear control that employs many nucleus-encoded protein cofactors from various families. For mitochondrial introns, only a few splicing factors have been characterized because disruption of their functions often causes embryo lethality. Here, we report the function of Empty Pericarp8 (Emp8) in the splicing of three group II introns in mitochondria, complex I biogenesis, and seed development in maize. Emp8 encodes a P subfamily pentatricopeptide repeat protein that localizes in mitochondria. The loss-of-function mutants of Emp8 are embryo lethal, showing severely arrested embryo and endosperm development in maize. The respiration rate in the emp8 mutants is reduced with substantially enhanced expression of alternative oxidases. Transcript analysis indicated that the trans-splicing of nad1 intron 4 and cis-splicing of nad4 intron 1 are abolished, and the cis-splicing of nad2 intron 1 is severely impaired in the emp8 mutants. These defects consequently lead to the disassembly of mitochondrial complex I and a dramatic reduction in its activity. Together, these results suggest that Emp8 is required for the trans-splicing of nad1 intron 4 and cis-splicing of nad4 intron 1 and nad2 intron 1, which is essential to mitochondrial complex I assembly and hence to embryogenesis and endosperm development in maize.
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