The ADH7 Promoter of Saccharomyces cerevisiae is Vanillin-Inducible and Enables mRNA Translation Under Severe Vanillin Stress.

Vanillin is one of the major phenolic aldehyde compounds derived from lignocellulosic biomass and acts as a potent fermentation inhibitor to repress the growth and fermentative ability of yeast. Vanillin can be reduced to its less toxic form, vanillyl alcohol, by the yeast NADPH-dependent medium chain alcohol dehydrogenases, Adh6 and Adh7. However, there is little information available regarding the regulation of their gene expression upon severe vanillin stress, which has been shown to repress the bulk translation activity in yeast cells. Therefore, in this study, we investigated expression patterns of the ADH6 and ADH7 genes in the presence of high concentrations of vanillin. We found that although both genes were transcriptionally upregulated by vanillin stress, they showed different protein expression patterns in response to vanillin. Expression of Adh6 was constitutive and gradually decreased under vanillin stress, whereas expression of Adh7 was inducible, and, importantly, occurred under severe vanillin stress. The null mutants of ADH6 or ADH7 genes were hypersensitive to vanillin and reduced vanillin less efficiently than the wild type, confirming the importance of Adh6 and Adh7 in vanillin detoxification. Additionally, we demonstrate that the ADH7 promoter is vanillin-inducible and enables effective protein synthesis even under severe vanillin stress, and it may be useful for the improvement of vanillin-tolerance and biofuel production efficiency via modification of yeast gene expression in the presence of high concentrations of vanillin.

香草醛是源自木质纤维素生物质的主要酚醛化合物之一，是一种强效的发酵抑制剂，可抑制酵母的生长和发酵能力。香草醛可通过酵母中依赖NADPH的中链醇脱氢酶Adh6和Adh7还原为毒性较低的形式——香草醇。然而，关于在严重香草醛胁迫下它们基因表达的调控信息却很少，而这种胁迫已被证明会抑制酵母细胞中的大量翻译活动。因此，在本研究中，我们研究了在高浓度香草醛存在下ADH6和ADH7基因的表达模式。我们发现，尽管这两个基因在转录水平上都受到香草醛胁迫的上调，但它们在响应香草醛时表现出不同的蛋白质表达模式。Adh6的表达是组成型的，在香草醛胁迫下逐渐降低，而Adh7的表达是可诱导的，且重要的是，在严重香草醛胁迫下发生。ADH6或ADH7基因的缺失突变体对香草醛高度敏感，并且比野生型更低效地还原香草醛，这证实了Adh6和Adh7在香草醛解毒中的重要性。此外，我们证明ADH7启动子是香草醛诱导型的，即使在严重香草醛胁迫下也能实现有效的蛋白质合成，并且它可能有助于通过在高浓度香草醛存在下修饰酵母基因表达来提高香草醛耐受性和生物燃料生产效率。