Preliminary Study On The Mechanism Of Ningnanmycin Mediated-Resistance To Tobacco Mosaic Virus

Mosaic disease of tobacco has caused a great damage on agricultural production in China.Tobacco mosaic virus(TMV)is the main casual agent of mosaic disease of tobacco.It is one of the ten most important viruses in the world.Ningnanmycin(NNM)has obvious anti-TMV activity,and is an efficient,low-toxicity,environment-friendly antiviral pesticide.Some progress has been made on the mechanism of NNM against TMV.However,effect of NNM has on systemic infection of TMV,in Nicotiana tabacum,and influence of NNM on expression level of DNA methylation related genes is not clear.Half leaf method using Nicotiana glutinosa is commonly used to screen antiviral drug.In this study,the half leaf method was optimized and the curative,protective and inactivation efficacies of NNM against TMV were verified.Impact of NNM has on local infection and systemic infection of TMV on Nicotiana tabacum was further investigated.Moreover,impact of NNM on expression level of DNA methylation-related genes was analyzed for the first time.Here were the results in this paper:Half-leaf method was optimized from three aspects: culture temperature,TMV concentration and virus inoculation method.It is verified that curative,protective and inactivation efficacies of NNM against TMV,with inhibition rate of 71.26%,57.69%,51.22%,respectively.The earliest infection timepoints of TMV in inoculated and systemic leaves were 12 hpi(hours post inoculaton)and 3 dpi(days post inoculation),respectively.Accumulation of TMV in inoculated leaves of Nicotiana tabacum decreased significantly by treatment of NNM.Although NNM treatment did not significantly affect TMV accumulation on upper leaves,it delayed the disease symptom caused by TMV infection on upper leaves.Expression level of DNA methylation-related genes was analyzed through RT-qPCR in inoculated leaves of N.tabacum treated with sterilized water,NNM,TMV,NNM+TMV,respectively.The results showed that NNM treatment significantly reduced the expression level of DNA methyltransferase DRM2.Expression level of DNA methyltransferase MET1,DRM2 and DNA demethyltransferase ROS1 and DML2 was significantly down-regulated caused by NNM treatment in TMV-infected inoculated leaves.