Abstract

Abstract This thesis investigates the role of an Armadillo repeat-containing (ARM) protein in Arabidopsis thaliana, focusing on its involvement in light signaling and abiotic stress responses. Although ARM proteins are recognized as integrators of environmental signals, their specific roles in coordinating light and stress responses remain poorly understood. To address this, phenotypic analyses were performed using Col-0 wild type, arm-1, hy5-2, phyB single mutants and hy5-2 arm, phyB arm double mutants under salinity (NaCl), osmotic (mannitol), varying light and temperature regimes, and heat stress (38–45°C). Seed germination assays demonstrated that both salinity and osmotic stress progressively inhibited germination in Col-0 and arm-1 seedlings, with stronger suppression under dark conditions. Under salinity stress in darkness, Col-0 consistently exhibited lower germination rates than arm-1, whereas no genotype-dependent differences were observed under control or osmotic stress conditions. Notably, salt stress exerted a more pronounced inhibitory effect on germination in the dark than mannitol treatment, suggesting a light-dependent role for ARM in early stress responses. Hypocotyl elongation analyses of Col-0 and arm-1 revealed light and temperature-dependent growth responses across the genotypes, with longer hypocotyls being recorded at elevated temperature (28°C). Heat stress inhibited hypocotyl elongation in both Col-0 and arm-1 seedlings, with longer hypocotyls observed in Col-0 at 38°C when compared with arm-1, while severe stress at 45°C resulted in comparable hypocotyl inhibition in both genotypes. Collectively, these findings suggest that ARM may contribute to the regulation of growth and stress adaptation under moderate environmental conditions, but its protective function may be diminished under severe stress. …víceméně