Gluconolactone induces cellulase gene expression in cellulolytic filamentous fungus Trichoderma reesei

Abstract

Filamentous fungus Trichoderma reesei is well known for its high capacity of producing cellulases for industrial application. Besides crystalline cellulose, several soluble sugars including cellobiose can effectively induce cellulase formation. In this study, gluconolactone, previously reported as a β-glucosidase inhibitor, was demonstrated to be capable of inducing cellulase gene expression at a level equivalent to that induced by cellobiose. Gluconolactone-induced formation of cellulase was abolished in T. reesei strain lacking Xyr1 or Crt1, two key regulators for cellulase gene expression. The induced expression of cellulase gene cbh1 was eliminated in the absence of intracellular β-glucosidase Cel1a on gluconolactone while it was hardly affected by the absence of extracellular β-glucosidase Bgl1. We further found that the absence of a cellobiose/glucose transporter Stp1 compromised cellulase production and led to a lower consumption of extracellular gluconolactone. These results suggest that the gluconolactone-derived inducing signal involves both its sensing at the membrane and its intracellular delivery for further processing to initiate cellulase formation.