Transcriptional analysis of the lichenase-like gene cel12A of the filamentous fungus Stachybotrys atra BP-A and its relevance for lignocellulose depolymerization

Abstract

To rationally optimize the production of industrial enzymes by molecular means requires previous knowledge of the regulatory circuits controlling the expression of the corresponding genes. The genus Stachybotrys is an outstanding producer of cellulosedegrading enzymes. Previous studies isolated and characterized the lichenase-like/non-typical cellulase Cel12A of S. atra (AKA S. chartarum) belonging to glycosyl hydrolase family 12 (GH12). In this study, we used RT-qPCR to determine the pattern of expression of cel12A under different carbon sources and initial ambient pH. Among the carbon sources examined, rice straw triggered a greater increase in the expression of cel12A than 1% lactose or 0.1% glucose, indicating specific induction by rice straw. In contrast, cel12A was repressed in the presence of glucose even when combined with this inducer. The proximity of 2 adjacent 5′-CTGGGGTCTGGGG-3′ CreA consensus target sites to the translational start site of cel12A strongly suggests that the carbon catabolite repression observed is directly mediated by CreA. Ambient pH did not have a significant effect on cel12A expression. These findings present new knowledge on transcriptional regulatory networks in Stachybotrys associated with cellulose/hemicellulose depolymerization. Rational engineering of CreA to remove CCR could constitute a novel strategy for improving the production of Cel12A.

Stachybotrys chartarum—A Hidden Treasure: Secondary Metabolites, Bioactivities, and Biotechnological Relevance

“…Lichenases are produced by various microorganisms, including fungi and bacteria, and have remarkable applications in detergent, food, feed, brewing, and wine industries as well as biodiesel and bioethanol production [ 51 ]. The expression of the gene Cel12A isolated from rotting cellulose rag-associated- S. chartarum by Picart et al was triggered by rice straw than 0.1% glucose or 1% lactose [ 52 , 53 ]. The resulting enzyme Cel12A (GH12 family) had a lichenase potential.…”

“…It also exhibited high potential towards barley mixed glucans and lichenan and low effectiveness on cellulose. Hence, Cel12A could have potential applications in various industries [ 53 ].…”