RECA plays a dual role in the maintenance of chloroplast genome stability in Physcomitrella patens

Plant J. 2015 Nov;84(3):516-26. doi: 10.1111/tpj.13017. Epub 2015 Oct 15.


Chloroplast DNA (cpDNA) encodes essential genes for chloroplast functions, including photosynthesis. Homologous recombination occurs frequently in cpDNA; however, its significance and underlying mechanism remain poorly understood. In this study, we analyzed the role of a nuclear-encoded chloroplast-localized homolog of RecA recombinase, which is a key factor in homologous recombination in bacteria, in the moss Physcomitrella patens. Complete knockout (KO) of the P. patens chloroplast RecA homolog RECA2 caused a modest growth defect and conferred sensitivity to methyl methanesulfonate and UV. The KO mutant exhibited low recovery of cpDNA from methyl methanesulfonate damage, suggesting that RECA2 knockout impairs repair of damaged cpDNA. The RECA2 KO mutant also exhibited reduced cpDNA copy number and an elevated level of cpDNA molecule resulting from aberrant recombination between short dispersed repeats (13-63 bp), indicating that the RECA2 KO chloroplast genome was destabilized. Taken together, these data suggest a dual role for RECA2 in the maintenance of chloroplast genome stability: RECA2 suppresses aberrant recombination between short dispersed repeats and promotes repair of damaged DNA.

Keywords: DNA repair; Physcomitrella patens; RecA; chloroplast genome; dispersed repeats; recombination.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bryopsida / drug effects
  • Bryopsida / genetics*
  • Bryopsida / radiation effects
  • DNA Copy Number Variations
  • DNA Damage / genetics
  • DNA Repair
  • Gene Knockout Techniques
  • Genome, Chloroplast*
  • Genome, Plant
  • Genomic Instability*
  • Methyl Methanesulfonate / pharmacology
  • Mutation
  • Plant Proteins / genetics
  • Plant Proteins / metabolism*
  • Rec A Recombinases / genetics
  • Rec A Recombinases / metabolism*
  • Ultraviolet Rays


  • Plant Proteins
  • Methyl Methanesulfonate
  • Rec A Recombinases

Associated data

  • GENBANK/AB284535
  • RefSeq/NC_005087
  • RefSeq/NC_005353