Abstract
Our previous works have shown the involvement of protein phosphorylation in the early steps of hyperosmotic stress signaling. We performed phosphoproteomic analysis in search of proteins that are rapidly phosphorylated after the stress hyperosmotic treatment using rice cultured cell. alpha-Tubulin was among those which were suggested to be such proteins by this analysis. We confirmed the stress-induced rapid (within 5 minutes) phosphorylation of alpha-tubulin by the use of Phos-Tag SDS-PAGE. Further analysis revealed: (i) the phosphorylation is conserved in Arabidopsis; (ii) removal of stress leads to the dephosphorylation of alpha-tubulin; (iii) the phosphorylation site is Thr349, which is conserved residue in alpha-tubulins and is located on the interaction surface of alpha/beta-tubulin heterodimers in the microtubule; (iv) the phosphorylated alpha-tubulin can be incorporated into microtubule. Based on these and other results, we will discuss the physiological significance of the alpha-tubulin phosphorylation in stress responses in plants.
