Molecular Mechanism Of FolmiR1 Confers The Pathogenicity Of Fusarium Oxysporum In Tomato Wilt Disease

Tomato wilt caused by Fusarium oxysporum f.sp.lycopersici(Fol)is a soil-borne fungal disease.Tomato wilt disease is also called "tomato cancer",severely threats to tomato production.Therefore,the prevention and control of tomato wilt disease is always a problem for tomato production,and required to understand the molecular mechanism of growth,development and pathogeneis of Fol.Recently,the availability of the genome sequences of both tomato and the fungal pathogen have not only accelerated the discovery of pathogenesis related genes but also provided a new platform to understand molecular pathogenesis at the genome level.Our previous studies have shown that FolmiRl from Fol can be transported into tomato and regulate the host immunate system by silencing disease defense-related target genes in tomato.In this study,FolmiRl was cloned and knocked out to study its biological function Compared to the wild type,there was no significant difference in growth of mycelia and the tolerance to abiotic stress in the knockout mutants.Further,The deletion of FolmiRl resulted in reducing pathogenicity of Fol.Our results showed that FolmiRl played an important role in the pathogenicity of Fol.Target gene FolCTS2 of FolmiRl was predicted in Fol.Functional domain prediction and conservation analysis revealed that the FolCTS2 was related to chitinase.This study revealed that FolCTS2 was not necessary for the growth of mycelia and the tolerance to abiotic stress.In addition,FolCTS2 did not participate in the pathogenicity regulation of Fol Chitinase activity analysis results revealed that deletion of FolCTS2 had no significant effects on the activity of chitinase,while the chitinase activity was significantly increased in the overexpressing strain.We surmised that the FolCTSs presented functional redundancy in Fol.Wether FolmiRl directly regulates the target gene FolCTS2 to perform its pathogenic function need further study.We found the functional redundancy gene FolCTS3 in Fol.The results showed that the loss of either FolCTS2 or FolCTS3 did not impair the growth of mycelia and the tolerance to abiotic stress in Fol.FolCTS3 was essential to the pathogenicity of Fol.In addition,we also found that the chitinase activity of FolCTS3 mutants was significantly reduced.Similarly,the chitinase activity of the deletion of FolCTS2/3 was also significantly reduced.It indicated that FolCTS2 and FolCTS3 are cooperatively involved in the pathogenicity of Fol.FolCTS2 and FolCTS3 play an important role in chitinase activity together,and FolCTS3 performed main functionsIn conclusion,this study clarified that the FolmiRl played an important role in the pathogenicity.Our findings revealed that FolCTS3 was required,at least in part,for virulence in Fol,which provided an important theoretical basis for the effective control of tomato wilt disease.