Identification of vanillic acid and its new amide derivative from Hyoscyamus niger and their modes of action in controlling tobacco mosaic virus

Abstract

Plant viruses represented by tobacco mosaic virus (TMV) are hard to control due to the characteristics of wide hosts and difficulties to be inactivated in vitro . The discovery of candidates to damage the virus directly, and elicitors to induce plant resistances are important strategies against TMV. This study aims to identify new candidates from the title plants as biopesticides in controlling TMV. Herein, vanillic acid ( 6 ) and its new amide derivative, nigeroate ( 1 ), and seven known ones were discovered from the seeds of Hyoscyamus niger L. Compound 1 , elucidated by spectral methods, was synthesized by two steps for industrial application in agriculture as a new elicitor. Compared with ningnanmycin, compound 1 appeared higher curative efficacies against TMV with the inhibitory rates of 58.00% and 69.14% at 250 and 500 μg/mL, respectively, while compound 6 displayed higher inactivation and protective efficacies with the inhibitory rates of 47.30–79.71% and 43.28–63.87% at 125–500 μg/mL, respectively. Compound 6 could destroy TMV particles into small fragments dramatically by decreasing the transcription level of TMV-CP gene, while compound 1 just broke the TMV particles slightly, and was no influence on TMV-CP gene. Interestingly, compound 1 induced potent hypersensitive response (HR), and systemic acquired resistance (SAR) activities (53.82% at 500 μg/mL) in tobaccos. The accumulation of H 2 O 2 by activating SOD (superoxide dismutase), CAT (catalase), as well as POD (peroxidase) was the mechanism of compound 1 induced HR. The SAR induced by compound 1 was referred to upregulate SA (salicylic acid) by activating PAL (phenylalanine ammonia-lyase) pathway, ICS (isochorismate synthase) pathway, as well as PR (pathogenesis-related) proteins due to the increasement of PAL enzyme, and PAL , ICS1 , NPR1 , PR1 , and PR2 transcription levels. Thus, vanillic acid ( 6 ) and its new amide derivative ( 1 ) could be developed as antiviral agents and plant immune elicitors for biopesticides in controlling TMV, respectively. • Vanillic acid and its new amide derivative, nigeroate, were identified from Hyoscyamus niger . • Tobacco mosaic virus coat protein is the target for vanillic acid exerting antiviral activity. • Nigeroate was synthesized by two steps for industrial application as an elicitor. • Accumulation of H 2 O 2 and salicylic acid contributed to nigeroate’s systemic resistance. • Defense enzymes, pathogenesis-related, and salicylic acid biosynthesis-related genes manipulated nigeroate’s resistance.