| Transcription factors（TFs）are DNA-binding proteins that regulate and activate the expression of downstream target genes by responding to upstream signal transduction pathways.A variety of transcription factors have been found in phytopathogenic fungi,which are involved in processes such as fungal growth and development,sporulation,secondary metabolism,and pathogenicity.It has been reported that multiple transcription factors play an important role in the growth,development and pathogenesis of Cochliobolus heterostrophus.Studies have shown that the b ZIP transcription factor Ada1（all development altered-1）in the model fungus Neurospora crassa regulates its growth and development and affects sexual reproduction,but the function of this transcription factor has not been reported in Corn southern leaf blight.Therefore,in this study,split-marker technology was used to construct a knockout mutant of the transcription factor ChAda1 of Cochliobolus heterostrophus.The main findings are as follows:（1）In terms of growth and development,the growth rate of theΔChada1 mutant decreased significantly,and the colony color changed from dark green to snow white.No conidia were produced.Analysis of the expression patterns of sporulation-related genes showed that the expressions of CON1,CON2,CON7,HTF1 and COS1 in theΔChada1 mutant were lower than those in the wild-type strain.The results indicated that the transcription factor ChAda1 may be involved in the regulation process of asexual reproduction in Cochliobolus heterostrophus.In addition,after sexual hybridization,it was found that compared with the wild-type strain,the number of black and white ascospores produced by theΔChada1 and the morphology of ascospores under microscopic observation did not change significantly.（2）In terms of resistance to oxygen stress,theΔChada1 showed lower tolerance to H2O2compared with the wild-type strain.The expression patterns of genes related to resistance to oxidative stress and regulation of redox balance were analyzed,and the expressions of CAT3,NOX1,NOX2,NOXD and NOXR were significantly decreased inΔChada1,indicating that the transcription factor ChAda1 may be involved in the response to oxidative stress.（3）In terms of secondary metabolites,the color of the liquid medium of theΔChada1changed from black to light milky white,the plate was more transparent,and the medium under the colony had no black precipitate,and the mycelium was white.The expression patterns of1,8-DHN melanin synthesis-related genes CMR1,PKS18,BRN1 and SCD1 were analyzed,and it was found that the expression of these genes in theΔChada1 mutant was significantly lower than that in the wild-type strain.The results indicated that the transcription factor ChAda1 may be involved in 1,8-DHN melanin synthesis.However,deletion of ChADA1 did not affect T-toxin production in Cochliobolus heterostrophus.（4）In terms of pathogenicity,in vitro maize leaf inoculation experiments showed that the lesions produced by theΔChada1 were five times smaller than those of the wild type,the leaves turned slightly yellow,and the pathogenicity was significantly reduced.Cellophane penetration experiments showed thatΔChada1 could form infected hyphae but the number and penetration ability were lower than wild-type strain.The results showed that the deletion of the transcription factor ChAda1 affects the regulation process of pathogenicity,as well as the number and penetration of infected hyphae.In conclusion,the transcription factor ChAda1 plays an important role in the growth,development and asexual reproduction of Cochliobolus heterostrophus,and is closely related to the resistance to oxygen stress and the production of 1,8-DHN melanin in Cochliobolus heterostrophus.In addition,ChAda1 is involved in the pathogenic process of Cochliobolus heterostrophus.This study preliminarily revealed the function of the transcription factor ChAda1 in Cochliobolus heterostrophus,which may provide a new target for the prevention and control of Cochliobolus heterostrophus. |
