CLR-4, a novel conserved transcription factor for cellulase gene expression in ascomycete fungi
CLR-4, a novel conserved transcription factor for cellulase gene expression in ascomycete fungi
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clr-4，子囊菌真菌纤维素酶基因表达的新型保守转录因子
DOI：
10.1111/mmi.14160
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发表时间：
2019-02-01
影响因子：
3.6
通讯作者：
Tian, Chaoguang
中科院分区：
文献类型：
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作者：
Liu, Qian;Li, Jingen;Tian, Chaoguang
木质纤维素生物质的真菌降解需要各种（半）纤维素酶，并且是天然碳循环的重要部分。虽然纤维素酶的诱导已被描述为一些腐殖丝状真菌，纤维素酶的转录调控是复杂的，许多方面仍然知之甚少。在这里，我们确定了新的纤维素酶调节因子NcR-4的粗糙脉孢菌和它的直系同源物MtR-4的嗜热毁丝霉的特点。缺失β-4导致类似缺陷的纤维素分解酶的生产和活动。Delta Ncclr-4/Delta Mtclr-4的转录组分析揭示了编码（半）纤维素酶和关键调节因子（clr-1、clr-2和xyr-1）的基因以及cAMP信号传导途径中的关键基因（如腺苷酸环化酶Nccr-1）的下调。在纤维素利用过程中，Delta Ncclr-4/Delta Mtclr-4的细胞内cAMP水平显著低于野生型。在电泳迁移率变动（EMSA）和DNA酶I足迹分析中，Nccr-4/Mtcr-4可直接与Nccr-1/Mtcr-1（编码腺苷酸环化酶）的启动子结合。EMSA还证明Ncx 4/Mtx 4可以直接结合clr-1（编码关键的纤维素酶调节剂）、Mtclr-2和Mtxyr-1（编码生物量解构调节剂）。这些关于新型纤维素酶表达调节剂Ncirp-4和Mtirp-4的发现丰富了我们对纤维素降解是如何调节的理解，并为工程真菌在生物炼制中解构植物生物质提供了新的靶点。
Fungal degradation of lignocellulosic biomass requires various (hemi-)cellulases and is an important part of the natural carbon cycle. Although induction of cellulases has been described for some saprobic filamentous fungi, the regulation of cellulase transcription is complex and many aspects are still poorly understood. Here, we identified and characterized the novel cellulase regulation factor NcCLR-4 in Neurospora crassa and its ortholog MtCLR-4 in Myceliophthora thermophila. Deletion of CLR-4 resulted in similarly defective cellulolytic enzyme production and activities. Transcriptome analyses of Delta Ncclr-4/Delta Mtclr-4 revealed the down-regulation of genes encoding (hemi-)cellulases and pivotal regulators (clr-1, clr-2 and xyr-1) and key genes in the cAMP signaling pathway such as adenylate cyclase Nccr-1. Intracellular cAMP levels were markedly lower in Delta Ncclr-4/Delta Mtclr-4 than in wild-type during cellulose utilization. In electrophoretic mobility shift (EMSA) and DNase I footprinting assays, NcCLR-4/MtCLR-4 can directly bound to the promoters of Nccr-1/Mtcr-1 (encoding adenylyl cyclase). EMSAs also demonstrated that NcCLR-4/MtCLR-4 could directly bound to clr-1 (encoding a key cellulase regulator), Mtclr-2 and Mtxyr-1 (encoding biomass deconstruction regulators). These findings about the novel cellulase expression regulators NcCLR-4 and MtCLR-4 enrich our understanding of how cellulose degradation is regulated and provide new targets for engineering fungi to deconstruct plant biomass in biorefineries.