MMR SYSTEM IN THE CROSSTALK BETWEEN DNA DAMAGE RESPONSE AND IMMUNE RESPONSE IN ARABIDOPSIS THALIANA

RAMOS, ROCÍO S.; SPAMPINATO, CLAUDIA P.

Mendoza

Congreso; LVIII Reunión Anual SAIB; 2022

As sessile organisms, plants are continuously exposed to a variety of adverse environmental factors. These factors, both biotic and abiotic, can cause damage to several biomolecules, such as DNA. Fortunately, all living organisms including plants have multiple mechanisms for detecting and repairing DNA damage in order to maintain the integrity of the genome. One of them is the DNA mismatch repair (MMR) system. MMR proteins are implicated in sensing and correcting DNA-replication associated errors and other nucleotide lesions induced by different stresses. Biotic stress and immune response in plants have been studied in depth and so have the responses to DNA damage. However, little information is available on the signaling crosstalk that occurs between DNA damage and biotic stress. The aim of this work was to study the role of MMR proteins during the immune response of Arabidopsis thaliana plants. Our previous data indicate that plants lacking the MutS homolog 6 (MSH6) were less susceptible to the bacterial pathogen Pseudomonas syringae pv. tomato strain DC3000 (Pst DC3000) than WT plants, probably due to the reduced stomatal opening observed in msh6 mutant plants. Here, we extended our research and observed bacteria-induced host DNA damage, but also found that msh6 mutant plants have increased levels of DNA double-strand breaks (DSBs) than WT plants under control conditions. Taking into account these observations, we measured the transcript levels of genes involved in both DNA DSB damage responses (RAD51D and SOG1 ) and immune responses (NPR1 and ICS ) and found that msh6 mutant plants have higher levels of these transcripts compared with WT plants. Since reactive oxygen species (ROS) are produced as a defense mechanism against pathogens and that these are known to damage DNA and regulate stomatal opening, we also investigated the response of msh6 mutant plants to hydrogen peroxide (H2O2) treatment and found that they were more affected than WT plants by this treatment. Moreover, we observed higher levels of H2O2 accumulation in msh6 mutant leaves compared with WT after staining with 3,3'-diaminobenzidine (DAB). Taken together, these results suggest that MSH6 could play a role in DSB response and in ROS homeostasis regulation in A. thaliana and highlight the high level of functional redundancy among DNA repair pathways. Future experiments will allow us to test this hypothesis.