Maize 14-3-3 protein ZmGF14-6 interacts with sugarcane mosaic virus HC-Pro and inhibits virus infection.

Sugarcane mosaic virus, belonging to the genus Potyvirus of the family Potyviridae, is an economically important pathogen infecting maize (Zea mays). Helper component-proteinase (HC-Pro), the potyviral RNA silencing suppressor (RSS), plays crucial roles in countering plants' anti-viral RNA silencing defense mechanisms. 14-3-3 proteins serve as critical regulators in plant response to various stresses. Our previous study had shown that the maize 14-3-3 protein ZmGF14-6 was a potential binding partner of SCMV HC-Pro. In this study, we showed that ZmGF14-6 could interact with SCMV HC-Pro using bimolecular fluorescence complementation, co-immunoprecipitation and luciferase complementation imaging assays. SCMV infection induced ZmGF14-6 expression in maize plants. Knockdown of ZmGF14-6 expression increased susceptibility of maize plants to SCMV infection, while co-expression of ZmGF14-6 inhibited SCMV infection. Furthermore, we revealed that co-expression of ZmGF14-6 led to the degradation of SCMV HC-Pro through the 26S proteasome pathway, thereby diminishing HC-Pro RSS activity. The dimerization of ZmGF14-6 was associated with its binding to HC-Pro and the inhibition of HC-Pro accumulation and SCMV infection. In summary, our findings revealed that the maize 14-3-3 protein ZmGF14-6, which was up-regulated in response to SCMV infection, interacted with HC-Pro to reduce its accumulation, thereby negatively regulating the susceptibility of maize plants to SCMV infection.