Homologous subunits of 1,3-beta-glucan synthase are important for spore wall assembly in Saccharomyces cerevisiae
Homologous subunits of 1,3-beta-glucan synthase are important for spore wall assembly in Saccharomyces cerevisiae
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DOI：
10.1128/ec.00200-06
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发表时间：
2007-02-01
期刊：
影响因子：
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通讯作者：
Ohya, Yoshikazu
中科院分区：
文献类型：
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作者：
Ishihara, Satoru;Hirata, Aiko;Ohya, Yoshikazu
在酿酒酵母的孢子形成过程中，四个单倍体核被包裹在多层孢子壁内。葡聚糖是孢子壁的主要成分，由1,3- β -葡聚糖合成酶合成，该合成酶由FKS1和FKS2编码的催化亚基组成。虽然通过同源性搜索发现了另一个由FKS3编码的同源物，但其功能尚不清楚。在本报告中，我们发现FKS2和FKS3是孢子壁组装所必需的。fk2和fks3突变体的子囊孢子被异常孢子壁包裹，对乙醚、高温和乙醇的抗性降低。然而，FKS1基因的缺失不会导致孢子壁缺陷。FKS2启动子调控下表达Fks1p和Fks2p的融合基因的构建表明，Fks2p驱动的Fks1p和Fks2p转化的asci对高温具有抗性，这表明FKS2的表达在孢子壁组装中起重要作用。fks1p驱动的Fks3p在营养生长过程中的表达对体外1,3-葡聚糖合成酶活性没有影响，但通过稳定葡聚糖合成酶调控亚基Rho1p，有效抑制了温度敏感突变体fks1的生长缺陷。基于这些结果，我们提出FKS2编码孢子形成过程中的初级1,3- β -葡聚糖合成酶，并且FKS3是正常孢子壁形成所必需的，因为它影响1,3- β -葡聚糖合成酶的上游调控。
During sporulation in Saccharomyces cerevisiae, the four haploid nuclei are encapsulated within multillayered spore walls. Glucan, the major constituent of the spore wall, is synthesized by 1,3-beta-glucan synthase, which is composed of a putative catalytic subunit encoded by FKS1 and FKS2. Although another homollog, encoded by FKS3, was identified by homology searching, its function is unknown. In this report, we show that FKS2 and FKS3 are required for spore wall assembly. The ascospores of fk2 and fks3 mutants were enveloped by an abnormal spore wall with reduced resistance to diethyl ether, elevated temperatures, and ethanol. However, deletion of the FKS1 gene did not result in a defective spore wall. The construction of fusion genes that expressed Fks1p and Fks2p under the control of the FKS2 promoter revealed that asci transformed with FKS2p-driven Fks1p and Fks2p were resistant to elevated temperatures, which suggests that the expression of FKS2 plays an important role in spore wall assembly. The expression of FKS1p-driven Fks3p during vegetative growth did not affect 1,3-beta-glucan synthase activity in vitro but effectively suppressed the growth defect of the temperature-sensitive fks1 mutant by stabilizing Rho1p, which is a regulatory subunit of glucan synthase. Based on these results, we propose that FKS2 encodes the primary 1,3-beta-glucan synthase in sporulation and that FKS3 is required for normal spore wall formation because it affects the upstream regulation of 1,3-beta-glucan synthase.