Crude peptides extracted from dry mycelium of Penicillium chrysogenum serve as a micro-associated molecular pattern to induce systemic resistance against tobacco mosaic virus in tobacco

Abstract

Control of viral diseases using systemic resistance-inducing microbes and microbial metabolites/molecules is an established alternative strategy for inhibiting plant viruses. However, the mechanisms whereby virus infection is inhibited and restricted in plants expressing systemic resistance remains poorly understood. We have previously reported that an aqueous extract of the dry mycelium of Penicillium chrysogenum (DMP) can be used to protect tobacco plants against Tobacco mosaic virus (TMV). In this study, we investigated the effect of crude peptides derived from DMP (PDMP) in protecting Nicotiana glutinosa against TMV. The number and diameter of TMV lesions in plants pre-treated with PDMP were fewer and smaller, respectively, than those in control plants. The elevated expressions of PAL, PTI5, PR-1a, NPR1, PR-1b, and PDF1.2 detected in the induced and systemic leaves following PDMP treatment indicated that the PDMP induced basal and systemic resistance in N. glutinosa. Callose deposition and TMV-N gene-triggered hypersensitive response (HR) at the site of the TMV infection were identified as key factors restricting the movement of viruses. The levels of N gene transcripts, as well as those of the TMV-N gene-triggered HR-related genes HSR203J, AOXa, SIPK, and ZFT1 increased more rapidly after being challenged with TMV in N. glutinosa plants pre-treated with PDMP compared with the control plants. However, we detected no significant difference between PDMP-treated and control plants with respect to TMV-induced callose deposition, indicating that PDMP enhances the resistance of N. glutinosa against TMV by accelerating TMV-N gene-triggered-HR rather than by priming callose deposition.