Decreased susceptibility to Pseudomonas syringae infection in msh6 Arabidopsis thaliana mutant plants

RAMOS, ROCÍO; SPAMPINATO, CLAUDIA P.

Salta

Congreso; LV Reunión Anual de la Sociedad Argentina de Investigación Bioquímica (SAIB); 2019

DNA mismatch repair (MMR) proteins have been implicated in sensing and correcting DNA replication associated errors and in regulating cell cycle progression. In addition, MMR proteins are also involved in the recognition of nucleotide lesions induced by different stresses. Besides abiotic stresses, all organisms are also threatened by various pathogens. To avoid infection, organisms rely on their immune systems. Even though both DNA damage and immune responses have been studied in depth separately, whether and how they are connected are largely unknown. The aim of this work was to study the contribution of the MMR system in the susceptibility/resistance of Arabidopsis thaliana plants during the immune response. Initially, MutS homolog 6 (MSH6) was studied because it forms the major mismatch recognition complex (MSH6-MSH2). First, we spray infected 14 days-old WT and msh6 mutant plants with the bacterial pathogen Pseudomonas syringae pv. tomato strain DC3000 (Pst DC3000). Colony-forming units (CFU) were quantified in leaves from inoculated plants and growth parameters like rosette area, cell number and cell area were analyzed. We found that disruption of MSH6 in A. thaliana plants results in a less susceptibility to Pst DC3000 infection, which could be evidenced by a lower CFU amount, a lower plant growth decrease, a lower number of cells and a higher cell area in mutant than in WT plants at 3 days after inoculation. Additionally, homeologous recombination rate was measured in both genotypes. The recombination assay construct contains two overlapping 1.6% divergent halves of the β-glucuronidase (GUS) reporter gene and upon recombination leads to the formation of an active GUS gene. We observed that Pst DC3000 infection led to an increase in the homeologous recombination rate in WT plants. This increase was not evident in msh6 mutant plants, which already show a high recombination rate under control conditions. These results suggest that MSH6 would have a role in the A. thaliana immune response to Pst DC3000 probably associated to programmed cell death.