DdaCrz1, a C(2)H(2)-Type Transcription Factor, Regulates Growth, Conidiation, and Stress Resistance in the Nematode-Trapping Fungus Drechslerella dactyloides

The Ca(2+)/calmodulin-dependent signaling pathway regulates diverse cellular processes. Calcineurin is a calcium-dependent phosphatase acting in fungi mainly through Crz1, a zinc finger transcription factor. Although the likely involvement of Ca(2+) in fungal carnivorism has been documented, how Crz1 functions in nematode-trapping fungi remains unknown. Here, we identified the Crz1 gene (named as DdaCrz1) in Drechslerella dactyloides, a species that forms constricting rings to trap nematodes. The deletion of DdaCrz1 significantly reduced hyphal growth and conidiation, trap formation, and ring cell inflation. Moreover, the mutation increased sensitivity to Mn(2+) but decreased sensitivity to Ca(2+), Mg(2+), Zn(2+), and Li(+). Similarly, the mutant showed increased tolerance to osmotic stress but was more sensitive to Congo red, a cell wall-damaging agent. Our results confirmed the critical roles of the Ca(2+)/calmodulin-dependent signaling pathway in regulating growth, conidiation, and the stress response, and suggested its involvement in trapping nematodes.