Cellulase induction in Trichoderma reesei by cellulose requires its own basal expression
Cellulase induction in Trichoderma reesei by cellulose requires its own basal expression
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DOI：
10.1074/jbc.272.15.10169
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发表时间：
1997-04-11
影响因子：
4.8
通讯作者：
ElDorry, H
中科院分区：
文献类型：
--
作者：
CarleUrioste, JC;EscobarVera, J;ElDorry, H
在丝状真菌里氏木霉中，纤维素酶的诱导是令人费解的，我们以前提出的机制是基于未诱导的真菌中存在低水平的纤维素酶；这种基本的纤维素酶活性会消化释放纤维素的寡糖，这些寡糖可以进入细胞并触发纤维素酶的表达。我们现在提供的实验进一步支持这一模型，我们在这里表明，纤维素酶系统的两个成员cbh1和egl1的转录本存在于未诱导的里氏木霉细胞中，这些转录本在纤维素存在的情况下被诱导至少1100倍。我们还表明，由cbh1启动子驱动的含有潮霉素B抗性编码基因的构建体对在没有纤维素的情况下生长的里氏木霉细胞具有潮霉素B抗性。此外，当针对纤维素酶系统三个成员的反义RNA在体内表达时，纤维素诱导的cbh1转录本的产生被抑制。实验表明，胞外纤维素酶活性是纤维素诱导合成纤维素酶转录物的限速事件。结果表明，纤维素酶系统的基础表达是纤维素酶系统诱导自身转录物合成的关键条件。
The induction of cellulases by cellulose, an insoluble polymer, in the filamentous fungus Trichoderma reesei is puzzling, We previously proposed a mechanism that is based on the presence of low levels of cellulase in the uninduced fungus; this basal cellulase activity would digest cellulose-releasing oligosaccharides that could enter the cell and trigger expression of cellulases. We now present experiments that lend further support to this model, We show here that transcripts of two mem bers of the cellulase system, cbh1 and egl1, are present in uninduced T. reesei cells, These transcripts are induced at least 1100-fold in the presence of cellulose, We also show that a construct containing the hygromycin B resistance-encoding gene driven by the cbh1 promoter confers hygromycin B resistance to T. reesei cells grown in the absence of cellulose. Moreover, cellulose induced production of the cbh1 transcript was suppressed when antisense RNA against three members of the cellulase system was expressed in vivo. Experiments are presented indicating that extracellular cellulase activity is the rate-limiting event in induction of synthesis of the cellulase transcripts by cellulose, The results reveal a critical requirement for basal expression of the cellulase system for induction of synthesis of its own transcripts by cellulose.