Involvement of AtPolλ in the repair of high salt- and DNA cross-linking agent-induced double strand breaks in Arabidopsis

Plant Physiol. 2013 Jun;162(2):1195-210. doi: 10.1104/pp.113.219022. Epub 2013 May 9.


DNA polymerase λ (Pol λ) is the sole member of family X DNA polymerase in plants and plays a crucial role in nuclear DNA damage repair. Here, we report the transcriptional up-regulation of Arabidopsis (Arabidopsis thaliana) AtPolλ in response to abiotic and genotoxic stress, including salinity and the DNA cross-linking agent mitomycin C (MMC). The increased sensitivity of atpolλ knockout mutants toward high salinity and MMC treatments, with higher levels of accumulation of double strand breaks (DSBs) than wild-type plants and delayed repair of DSBs, has suggested the requirement of Pol λ in DSB repair in plants. AtPolλ overexpression moderately complemented the deficiency of DSB repair capacity in atpolλ mutants. Transcriptional up-regulation of major nonhomologous end joining (NHEJ) pathway genes KU80, X-RAY CROSS COMPLEMENTATION PROTEIN4 (XRCC4), and DNA Ligase4 (Lig4) along with AtPolλ in Arabidopsis seedlings, and the increased sensitivity of atpolλ-2/atxrcc4 and atpolλ-2/atlig4 double mutants toward high salinity and MMC treatments, indicated the involvement of NHEJ-mediated repair of salinity- and MMC-induced DSBs. The suppressed expression of NHEJ genes in atpolλ mutants suggested complex transcriptional regulation of NHEJ genes. Pol λ interacted directly with XRCC4 and Lig4 via its N-terminal breast cancer-associated C terminus (BRCT) domain in a yeast two-hybrid system, while increased sensitivity of BRCT-deficient Pol λ-expressing transgenic atpolλ-2 mutants toward genotoxins indicated the importance of the BRCT domain of AtPolλ in mediating the interactions for processing DSBs. Our findings provide evidence for the direct involvement of DNA Pol λ in the repair of DSBs in a plant genome.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / drug effects
  • Arabidopsis / genetics*
  • Arabidopsis / metabolism
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Cross-Linking Reagents / chemistry
  • Cross-Linking Reagents / pharmacology
  • DNA Breaks, Double-Stranded*
  • DNA Damage
  • DNA End-Joining Repair
  • DNA Ligases / genetics
  • DNA Ligases / metabolism
  • DNA Polymerase beta / genetics
  • DNA Polymerase beta / metabolism*
  • DNA Repair*
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism
  • DNA-Directed DNA Polymerase / genetics
  • DNA-Directed DNA Polymerase / metabolism*
  • Gene Expression Regulation, Plant
  • Genome, Plant
  • Meristem / metabolism
  • Mitomycin / pharmacology
  • Mutation
  • Plants, Genetically Modified
  • Salinity
  • Seedlings / drug effects
  • Seedlings / genetics
  • Seedlings / metabolism


  • Arabidopsis Proteins
  • Cross-Linking Reagents
  • DNA-Binding Proteins
  • XRCC4 protein, Arabidopsis
  • Mitomycin
  • DNA polymerase beta2
  • DNA Polymerase beta
  • DNA polymerase lambda, Arabidopsis
  • DNA-Directed DNA Polymerase
  • DNA Ligases
  • Lig4 protein, Arabidopsis