Expression of Arabidopsis gamma-tubulin in fission yeast reveals conserved and novel functions of gamma-tubulin.

gamma-Tubulin localizes to microtubule-organizing centers in animal and fungal cells where it is important for microtubule nucleation. Plant cells do not have morphologically defined microtubule organizing centers, however, and gamma-tubulin is distributed in small, discrete structures along microtubules. The great difference in distribution has prompted speculation that plant gamma-tubulins function differently from animal and fungal gamma-tubulins. We tested this possibility by expressing Arabidopsis gamma-tubulin in the fission yeast Schizosaccharomyces pombe. At high temperatures, the plant gamma-tubulin was able to bind to microtubule-organizing centers, nucleate microtubule assembly, and support the growth and replication of S. pombe cells lacking endogenous gamma-tubulin. However, the distribution of microtubules was abnormal as was cell morphology, and at low temperatures, cells were arrested in mitosis. These results reveal that Arabidopsis gamma-tubulin can carry out essential functions in S. pombe and is, thus, functionally conserved. The morphological abnormalities reveal that it cannot carry out some nonessential functions, however, and they underscore the importance of gamma-tubulin in morphogenesis of fission yeast cells and in maintaining normal interphase microtubule arrays.