Department of Biotechnology, Faculty of Bioresource Science, Akita Prefectural University, 241-438 Kaidoubata-Nishi, Shimoshinjyo-Nakano, Akita-shi, Akita Prefecture 010-0195, Japan.
J Biosci Bioeng. 2010 Jul;110(1):1-7. doi: 10.1016/j.jbiosc.2010.01.006. Epub 2010 Feb 8.
Industrial yeasts, including a sake yeast Kyokai no. 7 (K7), are generally unable to sporulate. In K7 (Saccharomyces cerevisiae) cells, IME1 transcription was not induced under sporulation conditions, and K7 cells partially restored sporulation ability when transformed with a multicopy plasmid bearing IME1. However, the mechanisms of sporulation incompetence in industrial yeasts are poorly understood. We demonstrated that the deletion of the G1 cyclin CLN3, a key activator of the cell cycle, allows K7 cells to induce IME1 transcription and sporulate under sporulation conditions. In K7 cells, CLN3 mRNA and protein were not down-regulated despite sporulation conditions. Moreover, using a two-hybrid assay, we found that Ime1-Ume6 interaction was promoted in Cln3-deficient K7 cells. Thus, Cln3 is involved in the mechanism underlying sporulation incompetence by inhibiting IME1 transcription and the Ime1-Ume6 interaction. Based on these findings, we hypothesize that the absence of transmission of nutrient starvation signals to CLN3 leads to sporulation incompetence in K7 cells.
工业酵母，包括清酒酵母 Kyokai no. 7（K7），通常不能形成孢子。在 K7（酿酒酵母）细胞中，IME1 转录在孢子形成条件下未被诱导，而当 K7 细胞被携带 IME1 的多拷贝质粒转化时，部分恢复了孢子形成能力。然而，工业酵母孢子形成能力不足的机制还知之甚少。我们证明，删除细胞周期的关键激活物 G1 周期蛋白 CLN3，允许 K7 细胞在孢子形成条件下诱导 IME1 转录和形成孢子。在 K7 细胞中，尽管存在孢子形成条件，CLN3 mRNA 和蛋白质并未下调。此外，通过双杂交测定，我们发现 Ime1-Ume6 相互作用在 Cln3 缺失的 K7 细胞中得到促进。因此，Cln3 通过抑制 IME1 转录和 Ime1-Ume6 相互作用参与了孢子形成能力不足的机制。基于这些发现，我们假设缺乏将营养饥饿信号传递到 CLN3 的机制导致了 K7 细胞的孢子形成能力不足。
