Ando Akira, Nakamura Toshihide, Murata Yoshinori, Takagi Hiroshi, Shima Jun
National Food Research Institute, Tsukuba, Ibaraki, Japan.
FEMS Yeast Res. 2007 Mar;7(2):244-53. doi: 10.1111/j.1567-1364.2006.00162.x. Epub 2006 Sep 21.
Yeasts used in bread making are exposed to freeze-thaw stress during frozen-dough baking. To clarify the genes required for freeze-thaw tolerance, genome-wide screening was performed using the complete deletion strain collection of diploid Saccharomyces cerevisiae. The screening identified 58 gene deletions that conferred freeze-thaw sensitivity. These genes were then classified based on their cellular function and on the localization of their products. The results showed that the genes required for freeze-thaw tolerance were frequently involved in vacuole functions and cell wall biogenesis. The highest numbers of gene products were components of vacuolar H(+)-ATPase. Next, the cross-sensitivity of the freeze-thaw-sensitive mutants to oxidative stress and to cell wall stress was studied; both of these are environmental stresses closely related to freeze-thaw stress. The results showed that defects in the functions of vacuolar H(+)-ATPase conferred sensitivity to oxidative stress and to cell wall stress. In contrast, defects in gene products involved in cell wall assembly conferred sensitivity to cell wall stress but not to oxidative stress. Our results suggest the presence of at least two different mechanisms of freeze-thaw injury: oxidative stress generated during the freeze-thaw process, and defects in cell wall assembly.
用于面包制作的酵母在冷冻面团烘焙过程中会受到冻融胁迫。为了阐明耐冻融所需的基因，利用二倍体酿酒酵母的完全缺失菌株库进行了全基因组筛选。筛选鉴定出58个导致冻融敏感性的基因缺失。然后根据这些基因的细胞功能及其产物的定位进行分类。结果表明，耐冻融所需的基因经常参与液泡功能和细胞壁生物合成。基因产物数量最多的是液泡H(+) -ATP酶的组成部分。接下来，研究了冻融敏感突变体对氧化应激和细胞壁应激的交叉敏感性；这两种都是与冻融应激密切相关的环境应激。结果表明，液泡H(+) -ATP酶功能缺陷导致对氧化应激和细胞壁应激敏感。相反，参与细胞壁组装的基因产物缺陷导致对细胞壁应激敏感，但对氧化应激不敏感。我们的结果表明至少存在两种不同的冻融损伤机制：冻融过程中产生的氧化应激，以及细胞壁组装缺陷。
