Mechanism of Zn2+ regulation of cellulase production in Trichoderma reesei Rut-C30
Li Ni, Jing Li, Yumeng Chen, Yaling Shen, Dongzhi Wei, Wei Wang
Abstract
Abstract Background Trichoderma reesei Rut-C30 is a hypercellulolytic mutant strain that degrades abundant sources of lignocellulosic plant biomass, yielding renewable biofuels. Although Zn 2+ is an activator of enzymes in almost all organisms, its effects on cellulase activity in T. reesei have yet to be reported. Results Although high concentrations of Zn 2+ severely suppressed the extension of T. reesei mycelia, the application of 1–4 mM Zn 2+ enhanced cellulase and xylanase production in the high-yielding cellulase-producing Rut-C30 strain of T. reesei . Expression of the major cellulase, xylanase, and two essential transcription activator genes ( xyr1 and ace3 ) increased in response to Zn 2+ stimulation. Transcriptome analysis revealed that the mRNA levels of plc-e encoding phospholipase C, which is involved in the calcium signaling pathway, were enhanced by Zn 2+ application. The disruption of plc-e abolished the cellulase-positive influence of Zn 2+ in the early phase of induction, indicating that plc-e is involved in Zn 2+ -induced cellulase production. Furthermore, treatment with LaCl 3 (a plasma membrane Ca 2+ channel blocker) and deletion of crz1 (calcineurin-responsive zinc finger transcription factor 1) indicated that calcium signaling is partially involved in this process. Moreover, we identified the zinc-responsive transcription factor zafA , the transcriptional levels of which declined in response to Zn 2+ stress. Deletion of zafA indicates that this factor plays a prominent role in mediating the Zn 2+ -induced excessive production of cellulase. Conclusions For the first time, we have demonstrated that Zn 2+ is toxic to T. reesei , although promotes a marked increase in cellulase production. This positive influence of Zn 2+ is facilitated by the plc-e gene and zafA transcription factor. These findings provide insights into the role of Zn 2+ in T. reesei and the mechanisms underlying signal transduction in cellulase synthesis.