Fig. 8

A mechanistic model of the Mn²⁺ stimulation of cellulase production in T. reesei. After addition of 10 mM MnCl₂, the intracellular Mn²⁺ content increases via Mn²⁺ transport proteins Tpho84-1 and Tpho84-2. Intracellular Mn²⁺ promotes a cytosolic Ca²⁺ burst that is required for cellulase gene transcription via Ca²⁺ signaling. After using LaCl₃ (plasma membrane Ca²⁺ channels blocker), we suggest that Ca²⁺ channels are responsible for the cytosolic Ca²⁺ burst and cellulase production induced by Mn²⁺. Furthermore, TPMR1 is one of the links between the channels of Mn²⁺ and Ca²⁺, which may function as a Mn²⁺/Ca²⁺ exchanger to regulate Mn²⁺ and Ca²⁺ homeostasis under Mn²⁺ stress. Mn²⁺ could also employ other as-yet-unidentified pathways to regulate cellulase production. The solid arrows indicate data supported by our own experiments; dashed arrows indicate undefined regulation