Effects Of Sclerotinia Sclerotiorum Nitrogen Metabolism Related Genes On Virulence

Sclerotinia sclerotiorum（Lib.）de Bary is a typical necrotrophic fungal pathogen,which is distributed worldwide and has a wide range of hosts.It can successfully infect 729species of plants in 75 families.As one of the important oil crops in China,Brassica napus has a large planting area.Sclerotinia disease caused by S.sclerotiorum infection greatly affect yield and causes huge economic losses.By analyzing the function and mechanism of pathogenic genes of S.sclerotiorum,we can provide a richer theoretical basis for the prevention and control of S.sclerotiorum.Exogenous application of nitrogen fertilizer is needed during the growth of B.napus.It is unclear whether exogenous application of nitrogen fertilizer will affect the virulence of S.sclerotiorum during the growth of B.napus.After spraying 5 mmol/L and 50mmol/L NH₄Cl on the leaves of field B.napus,S.sclerotiorum was inoculated.The results showed that the lesions expanded faster under the treatment of 50 mmol/L NH₄Cl,indicating that the existence of high concentration NH₄Cl on the leaves facilitate to the infection of S.sclerotiorum.Whole gene transcriptome data of S.sclerotiorum at virulence stage and q RT-PCR results showed that the expression of the gene encoding typeⅠglutamine aminotransferase（SS1G＿09620）and gene encoding isopenicillin N synthetase（SS1G＿07964）was increased significantly during infection.In order to clarify the role of these two genes in S.sclerotiorum,SS1G＿09620 and SS1G＿07964 knockout mutants were obtained by homologous recombination.The gene knockout mutants of SS1G＿09620 or SS1G＿07964 did not affect the mycelial growth rate,colony morphology,oxalic acid production ability and sclerotia formation ability of S.sclerotiorum.Furthermore,the virulence of these gene knockout mutants was not different from that of the wild type.However,under the treatment condition of 50 mmol/L NH₄Cl,The virulence of the knockout mutant of SS1G＿07964 was lower than that of the wild type strain 1980.The virulence of the knockout mutant of SS1G＿09620 is lower than that of the wild type 1980 under the treatment condition of 5 mmol/L NH₄Cl,indicating that the two genes may have different responses to different levels of NH₄Cl,thus affecting the virulence of S.sclerotiorum.In conclusion,we found that high concentration of NH₄Cl affect the infection of S.sclerotiorum,and although the knockout of SS1G＿09620 and SS1G＿07964 do not affect the virulence of S.sclerotiorum,NH₄Cl treatment has different effects on the virulence of different knockout transformants,and the specific mechanism needs to be further studied.