Fig. 2

PHS1 phosphorylates α-tubulin in response to hyperosmotic stress. Immunoblots using an antibody specifically recognizing α-tubulin phosphorylated at Thr349 (pT349) or a general antibody for α-tubulin. Experiments were repeated at least once with similar results. (a) Cells were treated with sea water at the indicated levels for 10 min. (b) Cells were treated with 0.3 M sorbitol or 0.15 M NaCl for 10 min. (c) Gene structure of C. reinhardtii, PHS1. The boxes and connecting lines indicate exons and introns, respectively. Insertion site of the aphVIII gene is shown. The tubulin kinase and phosphatase domains are shown in blue and red boxes, respectively. (d) Sorbitol treatment at 0.2 M for 10 min triggered tubulin phosphorylation in wild-type and complemented cells, but not in phs1 mutant cells