Interactions Between Sugarcane Mosaic Virus P3N-PIPO And Other Viral Protein

Sugarcane is an important sugar and energy crop.Sugarcane mosaic disease is one of the important virus diseases that seriously harm the production of sugarcane.One of the pathogens of sugarcane mosaic disease is the Sugarcane mosaic virus(SCMV),and the SCMV belongs to the genus of Potyvirus in the family of Potyviridae.Its genome is a single-stranded RNA.Intercellular movement is an indispensable step for plant viruses to establish systemic infection.The intercellular movement of virus is determined by a number of proteins encoded by the virus or the host plants.For potyviruses,helper components-protease(HC-Pro),movement protein(P3N-PIPO),cylindrical protein(CI),terminal binding protein(VPg),and coat protein(CP)are reported to be involved in the cell-to-cell movement.In this study,the interactions between SCMV-P3N-PIPO and other virus-encoded proteins were studied to enrich the knowledge of the interaction network of potyvirus virus-encoded proteins,and to provide experimental SCMV movement complexes.Thus to investigate the molecular mechanism of the cell-to-cell movement of SCMV.The main results are as follows:1.Through yeast two-hybrid(Y2H)assays,P3N-PIPO was found to interact with CI and HC-Pro.CI could interact with P3N-PIPO by interacting with P3N or interacted PIPO.However,HC-Pro could only interact with the P3N.Bimolecular fluorescence complementation(BiFC)assays gained the same results as Y2H.P3N-PIPO interacts with CI on the plasm membrane.Whereas no obvious specific location for the interaction between P3N or PIPO and CI.P3N-PIPO and HC-Pro interact on the cytoplasm,and also P3N and HC-Pro interact on the cytoplasm.2.HC-Pro was the virus silent suppressor,which could depress the RNA silencing of host defense response.In order to explore the impact of the interaction between P3N-PIPO and HC-Pro on the inhibitory activity of HC-Pro,we performed the following experiments.We constructed the expression vectors of HC-Pro and P3N-PIPO,respectively.Then HC-Pro and P3N-PIPO were transiently co-expressed in the 16C tobacco plants with GFP,respectively.The bright fluorescence of GFP from the 16C tobacco plants transiently expressed the HC-Pro was observed under UV,compared with the tobacco plants transiently expressed GFP.It suggested that the HC-Pro cloned in study can conduct its biological function.While P3N-PIPO,HC-Pro,and GFP were transiently co-expressed in the 16C tobacco plants,the brightness of GFP was almost the same as that of the tobacco plants co-expressed HC-Pro and GFP.Western blot assays were performed to confirm the above results.These results indicated that the interaction between P3N-PIPO and HC-Pro did not impact the activity of the silencing suppressor of HC-Pro.We speculate that the cell-to-cell movement of SCMV-HC-Pro was mediated by the interaction with P3N-PIPO.Also,HC-Pro could be a component of the virus movement complex.