For integrated and durable control of apple Valsa canker,the amino acid sequence characteris-tics of three MFS-coding genes of pathogen V.mali were analyzed.Quantitative real-time PCR(RT-qPCR)technology was used to analyze the expression levels of these three genes during the infection of V mali.Additionally,the function of these three MFS genes in vegetative growth,pathogenicity,and abiotic stress responses was analyzed using gene knockout and complementation approaches.The re-sults showed that the deduced amino acid sequences of polyproteins encoded by all the three genes pos-sess a conserved MFS domain,named as VmMFS1-VmMFS3.VmMFS1 and VmMFS2 are closely re-lated in evolution,whereas they are distant from VmMFS3 based on the phylogenetic analysis.The ex-pression of VmMFS1-VmMFS3 during V.mali infection was further determined and all were upregu-lated significantly.Compared with that of wild-type strain 03-8,the deletion mutants of VmMFS1-VmMFS3 show no noticeable difference in colony morphology,while the growth rate of deletion mu-tants was reduced to some extent.Importantly,the pathogenicity of VmMFS1-VmMFS3 deletion mu-tants was significantly reduced.In addition,VmMFS1-VmMFS3 deletion mutants exhibited no signifi-cant variation in their tolerance to H2O2 stress;however,they were more susceptible to NaCl stress.The gene complementation test showed that the complemented strains could restore the phenotypic defect of the gene deletion mutants to the level of the wild-type strain 03-8.
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