Journal
JOURNAL OF INTEGRATIVE PLANT BIOLOGY
Volume 64, Issue 10, Pages 1952-1965Publisher
WILEY
DOI: 10.1111/jipb.13338
Keywords
Arabidopsis; mitochondria; mtDNA replication; mtDNA recombination; SSB
Categories
Funding
- Natural Science Foundation Project of CQ CSTC [cstc2019jcyj-bsh0091]
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Faithful DNA replication is crucial for living organisms. This study reveals the roles of SSB1 and SSB2 proteins in maintaining mitochondrial DNA stability through regulating DNA replication and homologous recombination. The findings provide new insights into plant mitochondrial DNA maintenance.
Faithful DNA replication is one of the most essential processes in almost all living organisms. However, the proteins responsible for organellar DNA replication are still largely unknown in plants. Here, we show that the two mitochondrion-targeted single-stranded DNA-binding (SSB) proteins SSB1 and SSB2 directly interact with each other and act as key factors for mitochondrial DNA (mtDNA) maintenance, as their single or double loss-of-function mutants exhibit severe germination delay and growth retardation. The mtDNA levels in mutants lacking SSB1 and/or SSB2 function were two- to four-fold higher than in the wild-type (WT), revealing a negative role for SSB1/2 in regulating mtDNA replication. Genetic analysis indicated that SSB1 functions upstream of mitochondrial DNA POLYMERASE IA (POLIA) or POLIB in mtDNA replication, as mutation in either gene restored the high mtDNA copy number of the ssb1-1 mutant back to WT levels. In addition, SSB1 and SSB2 also participate in mitochondrial genome maintenance by influencing mtDNA homologous recombination (HR). Additional genetic analysis suggested that SSB1 functions upstream of ORGANELLAR SINGLE-STRANDED DNA-BINDING PROTEIN1 (OSB1) during mtDNA replication, while SSB1 may act downstream of OSB1 and MUTS HOMOLOG1 for mtDNA HR. Overall, our results yield new insights into the roles of the plant mitochondrion-targeted SSB proteins and OSB1 in maintaining mtDNA stability via affecting DNA replication and DNA HR.
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