Early plant defense-related responses triggered by a novel glycoprotein from Streptomycin

Abstract Background A novel glycoprotein from Streptomyces sp. ZX01, GP-1, has high activity against tobacco mosaic virus (TMV). With small molecular weight and water-soluble characteristics, GP-1 has tremendous commercial value. Though previous study indicated a plant immunity-inducing effect, the antiviral mechanism of GP-1 is still unclear. Results In this study, early plant defense-related responses, such as Ca2+ transient peak, callose apposition, oxidative burst, hypersensitive response (HR), programmed cell death (PCD), NO rising and stomatal closure, were thoroughly investigated and we studied the mechanism of how GP-1 can induce virus resistance in Nicotiana benthamiana in additional detail. Results showed that GP-1 could induce [Ca2+]cyt rapidly both in tobacco leaves and suspension cells, followed by ROS and NO elevation. Similar with typical pathogen-associated molecular patterns (PAMPs), GP-1 induces callose deposition and stomatal closure to form defense barriers for pathogen invasion. The expression of defense-related genes further supported these phenomena. The gene with CAM5 was obtained by RNA sequencing in Nicotiana benthamiana. Conclusions Through analyses of expression of SA, JA and CAM5, it was shown that GP-1 enhanced the virus resistance of tobacco by improving expression of CAM5 and the SA and JA content.