Originally published as Genetics Published Articles Ahead of Print on December 1, 2005.

Genetics, Vol. 172, 811-825, February 2006, Copyright © 2006
doi:10.1534/genetics.105.050906

zds1, a Novel Gene Encoding an Ortholog of Zds1 and Zds2, Controls Sexual Differentiation, Cell Wall Integrity and Cell Morphology in Fission Yeast

Miyo Yakura^*, Fumiyo Ozoe^*, Hideki Ishida, Tsuyoshi Nakagawa, Katsunori Tanaka^*, Hideyuki Matsuda^* and Makoto Kawamukai^*,1

^* Department of Life Science and Biotechnology, Department of Biological Science, Faculty of Life and Environmental Science and Center for Integrated Research in Science, Shimane University, Matsue 690-8504, Japan

¹ Corresponding author: Department of Life Science and Biotechnology, Faculty of Life and Environmental Science, Shimane University, 1060 Nishikawatsu, Matsue 690-8504, Japan.
E-mail: kawamuka{at}life.shimane-u.ac.jp

While screening for genes that reverse the sporulation-deficient phenotype of the ras1 diploid Schizosaccharomyces pombe strain, we identified zds1. This gene shares sequence homology with the ZDS1 and ZDS2 genes from Saccharomyces cerevisiae, which appear to be involved in multiple cellular events. Expression of Zds1 in ras1 diploid cells elevated their sporulation rate from 0.3 to 11.2%. Expression of the Zds1 C-terminal region increased the sporulation rate further (to 21.9%) while introduction of the Zds1 N-terminal region had no effect. zds1 expression did not induce sporulation in strains with mutations in genes participating in the downstream MAP kinase cascade. The zds1-disrupted strain is sensitive to CaCl₂, and this effect is suppressed by the C-terminal region of Zds1. The growth of the zds1 strain is markedly inhibited by cold temperatures, while its viability decreased in the stationary phase. Moreover, the zds1 strain is round in shape and very sensitive to zymolyase, and its cell wall becomes thicker than that of wild type. Thus, zds1 must be required to maintain cell wall integrity. The Zds1–GFP fusion protein localized to the cytosol, the septum, and the cell cortex. Its localization in the septum was dependent on its C-terminal region. Overexpression of the C-terminal region of Zds1 induced multi-septa and abnormal zygotes. We propose that the C-terminal region is the functional domain of Zds1 while the N-terminal region is a negative regulatory region. Thus, Zds1 is involved in multiple cellular events in fission yeast, including sexual differentiation, Ca²⁺ tolerance, cell wall integrity, viability in the stationary phase, and cell morphology.

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