National Research Institute of Brewing, 3-7-1 Kagamiyama, Higashi-Hiroshima 739-0046, Japan; Graduate School of Integrated Sciences for Life, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8530, Japan; Food Technology Research Center, Hiroshima Prefectural Technology Research Institute, 12-70 Hijiyamahonmachi, Minami-Ku, Hiroshima 732-0816, Japan.
National Research Institute of Brewing, 3-7-1 Kagamiyama, Higashi-Hiroshima 739-0046, Japan.
J Biosci Bioeng. 2020 Jun;129(6):706-714. doi: 10.1016/j.jbiosc.2020.01.005. Epub 2020 Feb 19.
Among sake yeast strains, Kyokai no. 7 (K7) and its closely related strains (K7 group) are predominantly used because of their excellent brewing properties. In the sake industrial sector, the need for various types of yeast strains is high. Although crossbreeding is an effective method for generating genetic diversity that should result in diverse characteristics, most K7 group strains lack normal sporulation ability, including the ability to undergo meiotic chromosomal recombination, which leads to difficulties in crossbreeding. Accordingly, the improvement of sake yeast strains primarily depends on mutagenesis and suitable selection in a stepwise manner. Our recent study revealed that the long-preserved sake yeast strain Hiroshima no. 6 (H6) does not belong to the K7 group despite genetically being extremely similar. In addition, H6 exhibited normal sporulation. Thus, we isolated haploid cells from H6 and mated them with previously isolated haploid cells of K7 group strains. The crossbred diploid strains had normal sporulation ability; hence, we performed tetrad analysis. The brewing characteristics of the obtained haploid set were extremely diverse. Principal component analysis based on the volatile and organic acid components measured using small-scale sake brewing tests revealed that the haploid strains derived from each diploid strain displayed a characteristic distribution. Thus, we demonstrated the availability of genetic crossbreeding using H6 with sporulation ability to facilitate both the development of novel sake yeast strains with many desirable characteristics and analyses of the function of sake yeast.
在清酒酵母菌株中，由于其出色的酿造特性，常使用清酒酵母 7 号（K7）及其密切相关的菌株（K7 群）。在清酒工业领域，对各种酵母菌株的需求很高。虽然杂交是产生遗传多样性的有效方法，应该会产生多样化的特性，但大多数 K7 群菌株缺乏正常的孢子形成能力，包括进行减数分裂染色体重组的能力，这导致杂交困难。因此，清酒酵母菌株的改良主要取决于逐步诱变和适当选择。我们最近的研究表明，尽管在遗传上极其相似，但长期保存的清酒酵母菌株广岛 6 号（H6）不属于 K7 群。此外，H6 表现出正常的孢子形成。因此，我们从 H6 中分离出单倍体细胞，并将其与先前分离的 K7 群菌株的单倍体细胞进行交配。杂交的二倍体菌株具有正常的孢子形成能力；因此，我们进行了四分体分析。从小规模清酒酿造试验中测量的挥发性和有机酸成分的角度进行主成分分析表明，从每个二倍体菌株获得的单倍体集具有极其多样化的酿造特性。因此，我们证明了使用具有孢子形成能力的 H6 进行遗传杂交的有效性，这有助于开发具有许多理想特性的新型清酒酵母菌株，并分析清酒酵母的功能。
