Fig. 4. Actin organization in cdk5^ts cells. (A) U. maydis contains a fimbrin-like gene, which is predicted to encode a protein of 615 amino acids that shares a similar domain structure with S. pombe Fim1 (SpFim1) and S. cerevisiae Sac6 (ScSac6). The P-values of the predicted Calponin-homology domains are given in the open boxes. (B) A Fim1-GFP fusion protein localizes to patches within the growing bud of many cells. This localization disappears after treatment with Latrunculin A, indicating that the patches are composed of F-actin. Bar, 3 µm. (C) Fim1-GFP containing actin patches are highly dynamic and move over short distances at the growth region (arrow). Elapsed time is given in seconds. Bar, 2 µm. (D) In temperature-sensitive cdk5^ts mutants at the permissive temperature (22°C) Fim1-GFP locates in the bud. Bar, 3 µm. (E) After 4-5 hours at the restrictive temperature (34°C) patches appear at the mother cell and the bud. Bar, 5 µm. (F) Statistics of E. In budding cdk5^ts mutant cells at the permissive temperature, most patches are located in the bud (22°C, gray bars), whereas are almost equally distributed between the mother cell and the bud at the restrictive temperature (34°C, black bars).