Identification And Functional Characterization Of The Transcription Factor FgCrz1A In Fusarium Graminearum

The zinc finger transcription factor Crz1 is an important down-stream regulator of calcium-dependent signaling pathways in many organisms.Crz1 has a C2H2 zinc finger motif.When the cytoplasmic Ca²⁺concentration increases,Crz1p receives stimulation and binds to the promoter region of the downstream gene to regulate downstream gene transcription and respond to external environmental stimuli.At present,the function of Crz1 in Fusarium graminearum remains unclear.In this study,we used the method of homologous recombination to knock out FGSG₀1341,FGSG₀6311,FGSG₁0470,FGSG₁3711 and other genes of Fusarium graminearum and screened out the homologue of Crz1 in F.graminearum FgCrz1A by Ca²⁺stress,Southern blot confirmed positive monoclonal transformants.The deletion mutantΔFgCrz1A showed a decrease in mycelial growth rate on the PDA medium and increased mycelial branching on CM medium.ΔFgCrz1A could not produce conidia,qRT-PCR detected the transcription level ofΔFgCrz1A related asexual genes during asexual reproduction,and the transcription levels of abaA and wetA decreased to varying degrees.The sexual reproduction ofΔFgCrz1A is blocked and no ascostic shell can be generated.The transcription level of related sexual genes during sexual reproduction was detected by qRT-PCR and the transcription levels of MAT1-1-1,MAT1-1-2,MAT1-1-3,and MAT1-2-1 inΔFgCrz1A were induced after the black light lamp induction,it is hundreds of times different from PH-1.The sensitivity ofΔFgCrz1A to metal cations Ca²⁺,Mg²⁺,Mn²⁺,and Li⁺increases,but the sensitivity to Zn²⁺decreases.Surprisingly,we found that the deletion mutant of FgCrz1A was more tolerant to osmotic stress and cell wall disruptors than wild-type.Pathogenicity was measured by connecting PH-1 andΔFgCrz1A to maize ears in the field wheat and corn stalks,indicating that the invasiveness of the mutants was significantly reduced in flowering wheat heads and corn stalks,and the DON ofΔFgCrz1A was reduced,and the result should also be confirmed.qRT-PCR detected the transcription level of TRI in the process of inducing toxin production.It was found that the transcription level of many genes were decreased inΔFgCrz1A,except for the TRI7 and TRI12,TRI7required for the synthesis of NIV and TRI12 required for the transportion of toxin.Taken together,the results of this study indicate that FgCrz1A plays critical roles not only in regulation of fungal development,secondary metabolism and virulence but also in multiple stress responses in F.graminearum.