Saucedo-García, MarianaGonzález-Córdova, Carla D.Ponce-Pineda, I. GiordanoCano-Ramírez, DoraRomero-Colín, Fernanda M.Arroyo-Pérez, Erik E.King-Díaz, BeatrizZavaleta Fernandez de Cordova, AlonsoGavilanes-Ruíz, Marina2023-04-110166-8595http://hdl.handle.net/1885/288218Exposure to low, non-freezing temperatures develops freezing tolerance in many plant species. Such process is called cold acclimation. Molecular changes undergone during cold acclimation are orchestrated by signalling networks including MAP kinases. Structure and function of chloroplasts are affected by low temperatures. The aim of this work was to study how the MAP kinases MPK3 and MPK6 are involved in the chloroplast performance upon a long period of cold acclimation. We used Arabidopsis thaliana wild type and mpk3 and mpk6 mutants. Adult plants were acclimated during 7 days at 4 °C and then measurements of PSII performance and chloroplast ultrastructure were carried out. Only the mpk6 acclimated plants showed a high freezing sensitivity. No differences in the PSII function were observed in the plants from the three genotypes exposed to non-acclimated or acclimated conditions. The acclimation of wild-type plants produced severe alterations in the ultrastructure of chloroplast and thylakoids, which was more accentuated in the mpk plants. However, only the mpk6 mutant was unable to internalize the damaged chloroplasts into the vacuole. These results indicate that cold acclimation induces alterations in the chloroplast architecture leading to preserve an optimal performance of PSII. MPK3 and MPK6 are necessary to regulate these morphological changes, but besides, MPK6 is needed to the vacuolization of the damaged chloroplasts, suggesting a role in the chloroplast recycling during cold acclimation. The latter could be quite relevant, since it could explain why this mutant is the only one showing an extremely low freezing tolerance.This work was fnanced by Dirección General de Asuntos del Personal Académico (DGAPA), UNAM (grants: PAPIIT IN222815 and IN220618), Consejo Nacional de Ciencia y Tecnología (CONACYT) (CB-2015 and 255265 to M.S.-G; CB-2014-01 and 238368 to M.G.-R) and Facultad de Química, UNAM (5000 9115).application/pdfen-AU© The Author(s), under exclusive licence to Springer Nature B.V. 2021Chl a fuorescenceChlorophagyCold acclimationFreezing toleranceMPK3MPK6202110.1007/s11120-021-00852-02022-01-23