Potential Involvement of KIN10 and KIN11 Catalytic Subunits of the SnRK1 Protein Kinase Complexes in the Regulation of Arabidopsis γ-Tubulin

SnRK1 protein kinases are integral components of cell signaling involved in stress response, regulation of energy metabolism, seed germination and maturation, autophagy, and other processes. Nevertheless, many functions of these protein kinases remain unknown. In order to study the intracellular localization of KIN10 (catalytic subunit of the SnRK1 protein kinase complexes), protoplasts of the wild A. thaliana ecotype (Col-0) were transformed with a construct that included the KIN10-RFP fusion gene. It was established that the chimeric KIN10-RFP protein was diffusely distributed in the cytoplasm; however, it was mainly localized on the cell periphery, in the region adjacent to the plasma membrane. The diffuse distribution of KIN10 and γ-tubulin in the cytoplasm of A. thaliana root cells was demonstrated by immunofluorescence microscopy. The patterns of γ-tubulin intracellular localization in the root cells of the kin10 and kin11 knockout mutants and wild type A. thaliana were shown to be different. The intensity of γ-tubulin fluorescence in both mutants was lower than in the wild type-plants: this may be indicative of certain impairments in the formation of γ-tubulin complexes in the mutants. A lower intensity of γ-tubulin fluorescence was also recorded in cells of all lines cultivated under the conditions of energy shortage. In particular, the lowest level of fluorescence was recorded in the kin10 and kin11 mutants exposed to this type of stress, and this may be indicative of the synergistic influence of simultaneous dysfunction of one of these genes and energy deficiency on the formation of γ-tubulin complexes (γTuSC and γTuRC). The results obtained demonstrate the possible involvement of SnRK1 (KIN10 and KIN11) in the physiological response of plants to energy stress. With the data on the possible phosphorylation of the Ser131 residue in plant γ-tubulin by KIN10 taken into account, it can be assumed that SnRK1 protein kinases are involved in the regulation of microtubule polymerization in plants.