LINK BETWEEN DNA MISMATCH REPAIR SYSTEM AND IMMUNE RESPONSE IN ARABIDOPSIS THALIANA

RAMOS, ROCÍO S.; SPAMPINATO, CLAUDIA P.

Virtual

Congreso; Reunión conjunta SAIB SAMIGE; 2021

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, 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. Upon pathogen invasion, reactive oxygen species (ROS) are produced. ROS levels are known to damage DNA and regulate stomatal opening. 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. In order to investigate the cause of this phenotype, we assess Pathogen-Related Proteins (PRs) transcript levels, both after infection with Pst DC3000 and after treatment with 500 μM salicylic acid (SA). Curiously, we found that msh6 plants show a lower expression of PR1 than WT plants both after infection and SA treatment. Since the main route of entry of these bacteria to the plant is through the stomata, we analyzed stomatal opening and found that it was reduced in msh6 compared with WT plants. Genetic complementation of msh6 mutant plants with MSH6pro:MSH6 restored the disease susceptible phenotype. Also, complemented plants showed a higher stomatal opening than msh6 mutant plants. These observations implicate a link between MSH6 and stomatal aperture that leads to enhanced pathogen resistance. Further investigations are needed to examine whether these responses solely depend on ROS signalling.