Genomic stability is altered in salt-treated AtMSH7 mutants

CHIRINOS-ARIAS, MICHELLE C.; SPAMPINATO, CLAUDIA P.

Virtual

Congreso; Reunión conjunta SAIB SAMIGE; 2021

DNA mismatch repair (MMR) is a highly conserved biological pathway that improves the fidelity of DNA by correcting single base-base mismatches and unpaired nucleotides that arise through replication errors. Plants encode MutS protein homologs (MSH) conserved among other eukaryotic organisms, but also contain an extra MSH polypeptide (MSH7). The Arabidopsis thaliana MutSγ (heterodimer of MSH2-MSH7) preferentially recognizes some base?base mismatches. Considering that soil salinity is one of the main causes of abiotic stress that can threaten genome integrity, we studied the effect of salt on genome stability of the tenth generation (G10) of msh7 T-DNA insertional mutant and wild type A. thaliana plants. Seeds were sown on agar plates containing 0.5X Murashige and Skoog medium (MS) and grown for 10 days at 22°C under a 16/8 light/dark photoperiod. Seedlings were then transferred to agar plates containing MS supplemented with 100 mM NaCl and grown for 48 hours. DNA of each plant was isolated before and after treatment. High Resolution Melting (HRM) and Inter Simple Sequence Repeats (ISSR) molecular markers were chosen to determine genome stability. HRM analysis was performed with specific primers designed for reported regions with frequent SNPs and COLD-PCR for mutant enrichment. We found that wild type plants under control and salt-treated conditions conserved the same melting curve pattern, while mutant plants under salt conditions showed a shift in the melting curve pattern with respect to the control. As for ISSRs, no polymorphisms were observed in wild type plants under control and treated conditions. However, the treated mutant genotype showed ISSR band losses compared with control plants, which indicates the presence of genomic mismatches that prevent ISSR primer annealing. Taken together, our results suggest that MSH7 is involved in salt stress-induced DNA damage response.