Role of the Nitrogen Metabolism Regulator TAM1 in Regulation of Cellulase Gene Expression in Trichoderma reesei
Role of the Nitrogen Metabolism Regulator TAM1 in Regulation of Cellulase Gene Expression in Trichoderma reesei
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DOI：
10.1128/aem.01421-22
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发表时间：
2023-01-05
影响因子：
4.4
通讯作者：
Liu, Weifeng
中科院分区：
文献类型：
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作者：
Yang, Renfei;Wang, Zhixing;Liu, Weifeng
转录调控因子能够整合细胞外营养信号并对各种代谢基因施加组合控制。因此，过多的这些因子构成了一个复杂的调控网络，确保快速和准确的细胞反应，以获取和利用nutrients. Trichoderma reesei丝状真菌是最多产的纤维素酶的生产者之一，并已被确立为研究调控真核基因表达机制的模式微生物。然而，参与纤维素酶基因复杂和严格调控的转录调控因子的鉴定和功能表征尚未完成。在此，发现Zn（II）（2）Cys（6）-型转录因子TAM 1与构巢曲霉TamA同源，参与氮代谢，不仅调节铵的利用，而且控制T. reesei。而三角洲tam 1与蛋白胨作为氮源培养没有表现出生长缺陷，观察到铵，它仍然是显着损害纤维素酶的生物合成。TAM 1的缺乏几乎完全废除了快速纤维素酶基因诱导在静息细胞诱导系统。过量表达的gdh 1编码的关键铵同化酶在三角洲tam 1拯救生长缺陷铵，但不是纤维素酶基因表达的缺陷。值得注意的是，TAM 1的Zn（II）（2）Cys（6）DNA结合基序的突变几乎不影响纤维素酶基因的表达，而缺少与TAM 1相互作用所需的C-末端12个氨基酸的截短的ARE 1突变体干扰纤维素酶的生物合成。Delta tam 1的纤维素酶诱导缺陷通过纤维素酶基因的关键反式激活因子XYR 1的过表达而被拯救。因此，我们的研究结果确定了氮代谢调节剂作为一个新的调制器参与诱导纤维素酶基因expression.IMPORTANCE转录调控能够整合细胞外营养信号，并施加各种代谢基因的组合控制。因此，过多的这些因子构成了复杂的调节网络，确保快速和准确的细胞反应，以获得和利用营养物质。尽管对Zn（II）（2）Cys（6）型转录调节因子TamA及其同源物在氮利用中的功能进行了深入的机制研究，但它们参与其他生理过程仍然是未知的。在这项研究中，我们证明了TAM 1在介导铵利用和诱导纤维素酶生产中发挥双重调节作用，这表明氮利用和纤维素酶生物合成之间存在潜在的收敛调节节点。这项研究不仅有助于揭示纤维素分解真菌中纤维素酶基因表达的复杂调控网络，而且有助于扩大我们对真菌策略的了解，以实现快速繁殖的高效和协调的营养获取。
Transcriptional regulators are able to integrate extracellular nutrient signals and exert a combinatorial control over various metabolic genes. A plethora of such factors therefore constitute a complex regulatory network ensuring rapid and accurate cellular response to acquire and utilize nutrients.The filamentous fungus Trichoderma reesei is one of the most prolific cellulase producers and has been established as a model microorganism for investigating mechanisms modulating eukaryotic gene expression. Identification and functional characterization of transcriptional regulators involved in complex and stringent regulation of cellulase genes are, however, not yet complete. Here, a Zn(II)(2)Cys(6)-type transcriptional factor TAM1 that is homologous to Aspergillus nidulans TamA involved in nitrogen metabolism, was found not only to regulate ammonium utilization but also to control cellulase gene expression in T. reesei. Whereas Delta tam1 cultivated with peptone as a nitrogen source did not exhibit a growth defect that was observed on ammonium, it was still significantly compromised in cellulase biosynthesis. The absence of TAM1 almost fully abrogated the rapid cellulase gene induction in a resting-cell-inducing system. Overexpression of gdh1 encoding the key ammonium assimilatory enzyme in Delta tam1 rescued the growth defect on ammonium but not the defect in cellulase gene expression. Of note, mutation of the Zn(II)(2)Cys(6) DNA-binding motif of TAM1 hardly affected cellulase gene expression, while a truncated ARE1 mutant lacking the C-terminal 12 amino acids that are required for the interaction with TAM1 interfered with cellulase biosynthesis. The defect in cellulase induction of Delta tam1 was rescued by overexpression of the key transactivator for cellulase gene, XYR1. Our results thus identify a nitrogen metabolism regulator as a new modulator participating in the regulation of induced cellulase gene expression.IMPORTANCE Transcriptional regulators are able to integrate extracellular nutrient signals and exert a combinatorial control over various metabolic genes. A plethora of such factors therefore constitute a complex regulatory network ensuring rapid and accurate cellular response to acquire and utilize nutrients. Despite the in-depth mechanistic studies of functions of the Zn(II)(2)Cys(6)-type transcriptional regulator TamA and its orthologues in nitrogen utilization, their involvement in additional physiological processes remains unknown. In this study, we demonstrated that TAM1 exerts a dual regulatory role in mediating ammonium utilization and induced cellulase production in the well known cellulolytic fungus Trichoderma reesei, suggesting a potentially converged regulatory node between nitrogen utilization and cellulase biosynthesis. This study not only contributes to unveiling the intricate regulatory network underlying cellulase gene expression in cellulolytic fungus but also helps expand our knowledge of fungal strategies to achieve efficient and coordinated nutrient acquisition for rapid propagation.