LINK BETWEEN DNA MISMATCH REPAIR SYSTEM AND IMMUNE RESPONSE IN Arabidopsis thaliana

RAMOS, ROCÍO SOLEDAD; CLAUDIA PATRICIA SPAMPINATO

Congreso; SAIB - SAMIGE Joint meeting 2021; 2021

SAIB

As sessile organisms, plants are continuously exposed to a variety of adverse environmental factors. These factors, both bioticand abiotic, can cause damage to several biomolecules, such as DNA. Fortunately, all living organisms including plants havemultiple mechanisms for detecting and repairing DNA damage in order to maintain the integrity of the genome. One of themis the DNA mismatch repair (MMR) system. MMR proteins are implicated in sensing and correcting DNA-replicationassociated errors and other nucleotide lesions induced by different stresses. Biotic stress and immune response in plants havebeen studied in depth and so have the responses to DNA damage, but whether and how they are connected are largely unknown.The aim of this work was to study the role of MMR proteins during the immune response of Arabidopsis thaliana plants. Ourprevious data indicate that plants lacking the MutS homolog 6 (MSH6) were less susceptible to the bacterial pathogenPseudomonas syringae pv. tomato strain DC3000 (Pst DC3000) than WT plants. In order to investigate the cause of thisphenotype, we assess Pathogen-Related Proteins (PRs) transcript levels, both after infection with Pst DC3000 and aftertreatment with salicylic acid (SA). Curiously, we found that msh6 plants show a lower expression of PR1 than WT plants bothafter infection and SA treatment. Since the main route of entry of these bacteria to the plant is through the stomata, we analyzedstomatal opening and found that it was reduced in msh6 compared with WT plants. Genetic complementation of msh6 mutantplants with MSH6pro:MSH6 restored the disease susceptible phenotype. Also, complemented plants showed a higher stomatalopening than msh6 mutant plants. These observations implicate a link between MSH6 and stomatal aperture that leads toenhanced pathogen resistance. Given that upon pathogen invasion, reactive oxygen species (ROS) are produced and that theseare known to damage DNA and regulate stomatal opening, further investigations are needed to examine whether theseresponses depend on ROS signalling.