AUTHOR=Xu Wenqiang , Fang Yu , Ding Mingyang , Ren Yajing , Meng Xiangfeng , Chen Guanjun , Zhang Weixin , Liu Weifeng 

TITLE=Elimination of the Sugar Transporter GAT1 Increased Xylanase I Production in Trichoderma reesei

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.810066

DOI=10.3389/fmicb.2022.810066

ISSN=1664-302X

ABSTRACT=<p>The filamentous fungus <italic>Trichoderma reesei</italic> secretes large quantities of cellulases and hemicellulases that have found wide applications in industry. Compared with extensive studies on the mechanism controlling cellulase gene expression, less is known about the regulatory mechanism behind xylanase gene expression. Herein, several putative sugar transporter encoding genes that showed significant upregulation on xylan were identified in <italic>T</italic>. <italic>reesei</italic>. Deletion of one such gene, <italic>gat1</italic>, resulted in increased xylanase production but hardly affected cellulase induction. Further analyses demonstrated that deletion of <italic>gat1</italic> markedly increased XYNI production at the transcriptional level and only exerted a minor effect on XYNII synthesis. In contrast, overexpressing <italic>gat1</italic> caused a continuous decrease in <italic>xyn1</italic> expression. Deletion of <italic>gat1</italic> also affected the expression of <italic>xyn1</italic> and pectinase genes when <italic>T</italic>. <italic>reesei</italic> was cultivated with galacturonic acid as the sole carbon source. Transcriptome analyses of Δ<italic>gat1</italic> and its parental strain identified 255 differentially expressed genes that are enriched in categories of glycoside hydrolases, lipid metabolism, transporters, and transcriptional factors. The results thus implicate a repressive role of the sugar transporter GAT1 in <italic>xyn1</italic> expression and reveal that distinct regulatory mechanisms may exist in controlling the expression of different xylanase genes in <italic>T</italic>. <italic>reesei</italic>.</p>