Intracellular β-Glucosidases CEL1a and CEL1b Are Essential for Cellulase Induction on Lactose in Trichoderma reesei
Intracellular β-Glucosidases CEL1a and CEL1b Are Essential for Cellulase Induction on Lactose in Trichoderma reesei
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DOI：
10.1128/ec.00100-14
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发表时间：
2014-08-01
期刊：
影响因子：
--
通讯作者：
Liu, Weifeng
中科院分区：
文献类型：
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作者：
Xu, Jintao;Zhao, Guolei;Liu, Weifeng
乳糖（1，4 - 0-β-D-半乳糖-吡喃糖基-D-葡萄糖）诱导里氏木霉中的纤维素分解酶，并且实际上是用于在工业水平上生产纤维素酶的最重要的可溶性碳源之一。然而，诱导的机制尚未完全理解。在本研究中，我们研究了细胞内β-葡萄糖氧化酶CEL 1a和CEL 1b在乳糖诱导T. reesei。我们证明，虽然CEL 1a和CEL 1b在介导诱导的功能上是等同的，但同时缺乏这些细胞内β-葡糖苷酶会废除乳糖上的cbh 1基因表达。D-半乳糖恢复有效的纤维素酶基因诱导在Delta cel 1a菌株独立的还原代谢，但不是在Delta cel 1a Delta cel 1b菌株。进一步比较补充野生型CEL 1a或无催化活性的CEL 1a版本的Delta cel 1a Delta cel 1b菌株和组成型表达CEL 1a或乳酸克鲁维酵母β-半乳糖苷酶LAC 4的Delta cel 1a菌株的转录反应，表明CEL 1a蛋白及其糖苷水解活性对于乳糖诱导纤维素酶是必不可少的。我们还提出了证据表明，细胞内β-葡萄糖苷酶介导的乳糖诱导进一步传达到XYR 1，以确保纤维素酶基因的有效诱导表达。
Lactose (1,4-O-beta-D-galacto-pyranosyl-D-glucose) induces cellulolytic enzymes in Trichoderma reesei and is in fact one of the most important soluble carbon sources used to produce cellulases on an industrial level. The mechanism underlying the induction is, however, not fully understood. In this study, we investigated the cellular functions of the intracellular beta-glucosidases CEL1a and CEL1b in the induction of cellulase genes by lactose in T. reesei. We demonstrated that while CEL1a and CEL1b were functionally equivalent in mediating the induction, the simultaneous absence of these intracellular beta-glucosidases abolished cbh1 gene expression on lactose. D-Galactose restored the efficient cellulase gene induction in the Delta cel1a strain independently of its reductive metabolism, but not in the Delta cel1a Delta cel1b strain. A further comparison of the transcriptional responses of the Delta cel1a Delta cel1b strain complemented with wild-type CEL1a or a catalytically inactive CEL1a version and the Delta cel1a strain constitutively expressing CEL1a or the Kluyveromyces lactis beta-galactosidase LAC4 showed that both the CEL1a protein and its glycoside hydrolytic activity were indispensable for cellulase induction by lactose. We also present evidence that intracellular beta-glucosidase-mediated lactose induction is further conveyed to XYR1 to ensure the efficiently induced expression of cellulase genes.