The Role of SnRK1 Kinase in the Response of the Photosynthetic Machinery to Salinity Stress

In plants, SnRK1 (Sucrose non-fermenting-Related protein Kinase 1) is one of the major activators of catabolic processes, including autophagy, during stress responses. SnRK1 generally acts as a sensor of the energy status of the cell. Photosynthesis is by far the largest energy-supplying process in green plant cells exposed to light; thus, SnRK1 might participate in its regulation. In leaves of Arabidopsis lines with different levels of the catalytic subunit of SnRK1, KIN10, quantum yields of photosystems and of non-photochemical quenching, formation of the transthylakoid proton motive force, and contents of ATP in seedlings were compared under optimal conditions and under salinity stress. We detected specific changes in the photochemical activity of the chloroplasts that were assigned to constant activation of SnRK1 in two lines with constitutive overexpression of KIN10, both under control conditions and under salinity stress. Furthermore, the inhibition of the SnRK1 activity by means of RNA interference in Arabidopsis led to a lack of response to salinity at the level of chloroplast photochemistry.