Studies On The Functions Of FoCdk7,FoCdk9, FoCdk10 And FoNot2 Gene In Pathogenicitv Of Fusarium Oxysporum F. Sp. Niveum

Watermelon wilt disease, caused by Fusarium oxysporum f.sp. niveum (Fon), is a devastating fungal disease of watermelon, which seriously threatens to the development of watermelon industry. However, the molecular mechanim of the pathogenicity in Fon is relatively lagging. The represent study focused on the functions of FoCdk7, FoCdk9 and FoCdk10 in the CDKs (Cyclin-dependent Kinases) family and FoNot2 gene of the CCR4-NOT2 (Carbon catabolite repressor 4, negative on TATA-less complex) in Fon pathogenicity and their possible mechanisms.Three genes from CDKs family, FoCdk7, FoCdk9 and FoCdk10, and one gene from CCR4-NOT complex, FoNot2, were identified and cloned from Fon. Targeted deletion mutants AFoCdk7, AFoCdk9, ΔFoCdk10 and AFoNot2 and their cooresponding complement transfromants AFoCdk7-C, AFoCdk9-C, AFoCdk10-C and AFoNot2-C were constructed. Mycelial growth phenotype, pathogenicity, stress response and fusaric acid (FA) content were analyzed by comparing between the wild type, the targeted deletion mutants and complement transfromants. Main results are as follows:(1) FoCdk7, FoCdk9, FoCdk10 and FoNot2 regulated fungal development, pigment biosynthesis, conidial development and pathogenicity in F. oxysporum f.sp. nievum by phenotype analysis and inoculation experiments, meanwhile they dramatically affected the penetration and perhaps been the leading reason to regulate pathogenicity.(2) Cell wall-damaging sensitivity analysis showed the deletion mutants AFoCdk7, AFoCdk9, AFoCdk10 and AFoNot2 affected the cell wall integrity, and six cell wall biosynthesis-related genes were exhibited regulated in the mutants. These results indicated FoCdk7, FoCdk9, FoCdk10 and FoNot2 directly or indirectly regulated the cell wall integrity pathway in F. oxysporum f.sp. nievum.(3) FoCdk7, FoCdk9, FoCdk10 and FoNot2 were required for response to oxidative stresses. All mutants exhibited decreased tolerance to oxidative stresses agents, and five peroxidase synthase related genes were down-regulated in the four mutants compared with wildtype. These results indicated FoCdk7, FoCdk9, FoCdk10 and FoNot2 regulated the oxidative stress resistance in F. oxysporum f.sp. nievum.(4) HPLC (High Performance Liquid Chromatography) analysis showed the FA (Fusaric acid) biosynthesis dramatically decreased in all deletion mutants. Simultaneously, the expression levels of six genes involved in FA biosynthesis were significantly reduced in mutants. These results indicated that FoCdk7, FoCdk9, FoCdk10 and FoNot2 played vital roles in involvement of FA production, which could be a critical factor in regulation of pathogenicity in F. oxysporum f.sp. nievum.Results of our study revealed that FoCdk7, FoCdk9, FoCdk10 and FoNot2 are important for various life processes of growth and development, environmental adaptability, pathogenicity and FA biosynthesis in F. oxysporum f.sp. nievum.