Functional Analysis Of Genes MfCdtf1,MfHMG5 And MfHMG6 In Monilinia Fructicola

As a serious fungal fruit disease,peach brown rot is widely distributed in China.It occurs in the main peach producing areas and seriously threats the peach industry.The causal agents of brown rot disease can be found in 22 provincial administrative regions.Among them,Monilinia fructicola is the predominant species.At present,the research about mechanisms of pathogenicity of M.fructicola is still very limited.Based on genomic and transcriptomic analysis during early stage of infection,MfCdtf1,MfHMG5 and MfHMG6 were selected as target genes to analyze their biological functions.Transcriptomic data showed that the expression of MfCdtf1 varied irregularly during the early stages of infection,e.g.,significantly increased at 1 h and 24 h,significantly decreased at spore germination stage,indicating that MfCdtf1 was most likely involved in the infection and spore germination.Three MfCdtf1 knockout transformants and three complemented transformants were obtained by split-marker method.Phenotypic investigation found that the knockout of MfCdtf1 gene reduced the growth rate and virulence of M.fructicola,decreased sporulation and pigment synthesis abilities.Stress tests showed that the growth rate of ΔMfCdtf1 was lower than that of wild-type strain Bmpc7,and the absence of MfCdtf1 reduced the sensitivity to exogenous stresses.Interestingly,two oxalic acid synthesis-related genes Mfsod1,Mfoah and three melanin synthesis-related genes Mf4 HNR,MfALB1 and MfBUF1 were downregulated in ΔMfCdtf1.Besides two genes involved in sporulation,MfHMG5 was significantly down-regulated,while MfHMG6 was up-regulated in ΔMfCdtf1.Nevertheless,the expression of MfHMG5 and MfHMG6 in the early stages of infection was similar,and both down-regulated significantly after 1 h.However,it was upregulated significantly at spore germination.The knockout and overexpression transformants of MfHMG5,and knockout and complemented transformants of MfHMG6 were obtained.It was found that the knockout and overexpression of MfHMG5 gene decreased the growth rate and sporulation ability,but did not affect the pathogenicity of M.fructicola.Knock out of MfHMG6 gene reduced the growth rate,virulence and sporulation ability of M.fructicola,and increased the expression of MfHMG5 gene.This study explored the functions of MfCdtf1,MfHMG5 and MfHMG6 genes in the growth and development of M.fructicola,as well as during the infection,which provided certain theoretical basis for management of peach brown rot disease.