Research Area of Gene Technology and Applied Biochemistry, Institute for Chemical Engineering, Vienna University of Technology, Vienna, Austria.
Appl Environ Microbiol. 2012 Apr;78(7):2168-78. doi: 10.1128/AEM.06959-11. Epub 2012 Jan 27.
The cyclic AMP (cAMP) pathway represents a central signaling cascade with crucial functions in all organisms. Previous studies of Trichoderma reesei (anamorph of Hypocrea jecorina) suggested a function of cAMP signaling in regulation of cellulase gene expression. We were therefore interested in how the crucial components of this pathway, adenylate cyclase (ACY1) and cAMP-dependent protein kinase A (PKA), would affect cellulase gene expression. We found that both ACY1 and PKA catalytic subunit 1 (PKAC1) are involved in regulation of vegetative growth but are not essential for sexual development. Interestingly, our results showed considerably increased transcript abundance of cellulase genes in darkness compared to light (light responsiveness) upon growth on lactose. This effect is strongly enhanced in mutant strains lacking PKAC1 or ACY1. Comparison to the wild type showed that ACY1 has a consistently positive effect on cellulase gene expression in light and darkness, while PKAC1 influences transcript levels of cellulase genes positively in light but negatively in darkness. A function of PKAC1 in light-modulated cellulase gene regulation is also reflected by altered complex formation within the cel6a/cbh2 promoter in light and darkness and in the absence of pkac1. Analysis of transcript levels of cellulase regulator genes indicates that the regulatory output of the cAMP pathway may be established via adjustment of XYR1 abundance. Consequently, both adenylate cyclase and protein kinase A are involved in light-modulated cellulase gene expression in T. reesei and have a dampening effect on the light responsiveness of this process.
环腺苷酸 (cAMP) 途径代表了一个中央信号级联，在所有生物中都具有至关重要的功能。先前对里氏木霉（Hypocrea jecorina 的无性型）的研究表明，cAMP 信号在调节纤维素酶基因表达中具有功能。因此，我们对该途径的关键组成部分，腺苷酸环化酶 (ACY1) 和 cAMP 依赖性蛋白激酶 A (PKA)，如何影响纤维素酶基因表达感兴趣。我们发现，ACY1 和 PKA 催化亚基 1 (PKAC1) 都参与了营养生长的调节，但对有性发育不是必需的。有趣的是，我们的结果表明，在以乳糖为碳源生长时，与光照相比，黑暗中纤维素酶基因的转录丰度明显增加（对光照的响应）。在缺乏 PKAC1 或 ACY1 的突变株中，这种效应得到了极大的增强。与野生型相比，ACY1 对光照和黑暗中纤维素酶基因的表达均具有一致的正效应，而 PKAC1 则在光照下正向影响纤维素酶基因的转录水平，而在黑暗中则负向影响。PKAC1 在光调节纤维素酶基因调控中的功能也反映在 cel6a/cbh2 启动子内的复合物形成在光照和黑暗中以及在没有 pkac1 的情况下发生了改变。纤维素酶调节基因转录水平的分析表明，cAMP 途径的调节输出可能是通过调整 XYR1 的丰度来建立的。因此，腺苷酸环化酶和蛋白激酶 A 都参与了里氏木霉的光调节纤维素酶基因表达，并对该过程的光照响应具有抑制作用。
