Functional conservation of MoCRZ1 in Magnaporthe oryzae and its orthologs in Fusarium graminearum and Neurospora crassa

Abstract

Calcium signaling is one of the most common and important signal transduction cascades present in any living organism and is said to be highly conserved in throughout evolution. In Magnaporthe oryzae, a rice blast pathogen, calcium signaling pathway is required for conidiation and infection-related development, which contributes to the pathogenicity of the fungus. M. oryzae calcineurin-responsive zinc finger 1 (MoCRZ1) is involved in the calcium-dependent signaling pathway of M. oryzae, which acts as a transcription factor. Deletion mutants of MoCRZ1 (∆Mocrz1) showed drastic reduction in conidiation, hypersensitivity to calcium and cell membrane destabilizing agents as well as dramatic reduction in virulence. In this study, the orthologs of MoCRZ1 in Fusarium graminearum (FgCRZ1) and Neurospora crassa (NcCRZ1) were identified using BLASTP. Domain analyses showed that FgCRZ1 and NcCRZ1, possess one calcineurin-docking domain and two C2H2 zinc finger domains, similar to MoCRZ1, suggesting that the orthologs interact with calcineurin and that they are transcription factors involved in calcium signaling. Transformations of FgCRZ1 or NcCRZ1 into ∆Mocrz1 complemented ∆Mocrz1 defects in conidiation, appresorial turgor generation and eventually restored the virulence of nearly non-pathogenic ∆Mocrz1. Both FgCRZ1 and NcCRZ1 were able to suppress the calcium sensitivity of ∆Mocrz1, however, only ΔMocrz1::NcCRZ1 was able to resist the cell wall disturbing agent (Congo red) and only ΔMocrz1::FgCRZ1 was tolerant to cell membrane destabilizing agent (SDS), showing selective complementation of cell wall and membrane stress intolerant phenotype of ∆Mocrz1. Taken altogether, these results suggest that FgCRZ1 and NcCRZ1 are calcineurin-responsive zinc finger transcription factors in F. graminearum and N. crassa, respectively, which are highly conserved despite of the differences of in lifestyle from which they belong, and could substitute the major roles of MoCRZ1 in conidiation, calcium sensitivity and virulence.