Trichoderma reesei is an ascomycete fungus that has a tremendous capability of secreting extracellular proteins, mostly lignocellulose-degrading enzymes. Although many aspects of the biology of this organism have been unfolded, the roles of the many sugar transporters coded in its genome are still a mystery with a few exceptions. One of the most interesting sugar transporters that has thus far been discovered is the cellulose response transporter 1 (CRT1), which has been suggested to be either a sugar transporter or a sensor due to its seemingly important role in cellulase induction. Here we show that CRT1 is a high-affinity cellobiose transporter, whose function can be complemented by the expression of other known cellobiose transporters. Expression of two sequence variants of the crt1 gene in Saccharomyces cerevisiae revealed that only the variant listed in the RUT-C30 genome annotation has the capability to transport cellobiose and lactose. When expressed in the $$\Delta$$ crt1 strain, the variant listed in the QM6a genome annotation offers partial complementation of the cellulase induction, while the expression of the RUT-C30 variant or cellobiose transporters from two other fungal species fully restore the cellulase induction. These results add to our knowledge about the fungal metabolism of cellulose-derived oligosaccharides, which have the capability of inducing the cellulase production in many species. They also help us to deepen our understanding of the T. reesei lactose metabolism, which can have important consequences as this sugar is used as the inducer of protein secretion in many industrial processes which employ this species.

中文翻译：

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对糖转运蛋白 CRT1 的研究揭示了对里氏木霉中纤维素酶诱导至关重要的新特征。

里氏木霉是一种子囊菌真菌，具有分泌细胞外蛋白质（主要是木质纤维素降解酶）的巨大能力。尽管这种生物体生物学的许多方面已经展开，但其基因组中编码的许多糖转运蛋白的作用仍然是一个谜，只有少数例外。迄今为止发现的最有趣的糖转运蛋白之一是纤维素反应转运蛋白 1 (CRT1)，由于其在纤维素酶诱导中的重要作用，它被认为是糖转运蛋白或传感器。在这里，我们表明 CRT1 是一种高亲和力的纤维二糖转运蛋白，其功能可以通过其他已知纤维二糖转运蛋白的表达来补充。crt1 基因在酿酒酵母中的两个序列变体的表达表明，只有 RUT-C30 基因组注释中列出的变体具有运输纤维二糖和乳糖的能力。当在 $$\Delta$$ crt1 菌株中表达时，QM6a 基因组注释中列出的变体提供了纤维素酶诱导的部分互补，而来自其他两种真菌物种的 RUT-C30 变体或纤维二糖转运蛋白的表达完全恢复了纤维素酶就职。这些结果增加了我们对纤维素衍生的寡糖的真菌代谢的认识，这些寡糖具有在许多物种中诱导纤维素酶产生的能力。它们还帮助我们加深对里氏木霉乳糖代谢的理解，