Trehalose is required for the acquisition of tolerance to a variety of stresses in the filamentous fungus Aspergillus nidulans
Trehalose is required for the acquisition of tolerance to a variety of stresses in the filamentous fungus Aspergillus nidulans
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DOI：
10.1099/00221287-147-7-1851
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发表时间：
2001-07-01
期刊：
影响因子：
2.8
通讯作者：
d'Enfert, C
中科院分区：
文献类型：
--
作者：
Fillinger, S;Chaveroche, MK;d'Enfert, C
海藻糖是一种非还原性二糖，在构巢曲霉的分生孢子中含量较高，在诱导分生孢子萌发时会迅速降解。此外，海藻糖会因热激或氧化应激而积累。作者对构巢曲霉编码海藻糖 - 6 - 磷酸合酶的tpsA基因进行了特性分析，该酶催化海藻糖生物合成的第一步。tpsA在酿酒酵母tps1突变体中的表达表明，tpsA基因产物与酵母Tps1海藻糖 - 6 - 磷酸合酶功能相当。构巢曲霉tpsA缺失突变体在分生孢子形成过程中或对各种应激条件都不产生海藻糖。tpsA突变体的白色萌发菌丝对中等应激条件（在45℃下生长或存在2 mM H₂O₂）的敏感性增加，它们对严重应激（在50℃下60分钟或存在100 mM H₂O₂）的反应与野生型萌发菌丝相似。此外，tpsA突变体的分生孢子在储存时活力迅速丧失。这些结果与海藻糖在获得应激耐受性中的作用一致。tpsA基因的失活还导致糖磷酸的稳态水平升高，但并不像在酿酒酵母中那样阻止在可快速代谢的碳源（葡萄糖、果糖）上的生长。这表明海藻糖6 - 磷酸是己糖激酶的一种生理抑制剂，但这种调控对于构巢曲霉中适当的糖酵解通量并非必需。有趣的是，tpsA转录不会因热激或在分生孢子形成过程中被诱导，这表明海藻糖的积累可能是由于海藻糖6 - 磷酸合酶的翻译后激活过程。
Trehalose is a non-reducing disaccharide found at high concentrations in Aspergillus nidulans conidia and rapidly degraded upon induction of conidial germination. Furthermore, trehalose is accumulated in response to a heat shock or to an oxidative shock. The authors have characterized the A. nidulans tpsA gene encoding trehalose-6-phosphate synthase, which catalyses the first step in trehalose biosynthesis. Expression of tpsA in a Saccharomyces cerevisiae tps1 mutant revealed that the tpsA gene product is a functional equivalent of the yeast Tps1 trehalose-6-phosphate synthase. The A. nidulans tpsA-null mutant does not produce trehalose during conidiation or in response to various stress conditions. White germlings of the tpsA mutant show an increased sensitivity to moderate stress conditions (growth at 45 degreesC or in the presence of 2 mM H2O2), they display a response to severe stress (60 min at 50 degreesC or in the presence of 100 mM H2O2) similar to that of wild-type germlings. Furthermore, conidia of the tpsA mutant show a rapid loss of viability upon storage. These results are consistent with a role of trehalose in the acquisition of stress tolerance. Inactivation of the tpsA gene also results in increased steady-state levels of sugar phosphates but does not prevent growth on rapidly metabolizable carbon sources (glucose, fructose) as seen in Saccharomyces cerevisiae. This suggests that trehalose 6-phosphate is a physiological inhibitor of hexokinase but that this control is not essential for proper glycolytic flux in A. nidulans. Interestingly, tpsA transcription is not induced in response to heat shock or during conidiation, indicating that trehalose accumulation is probably due to a post-translational activation process of the trehalose 6-phosphate synthase.