Abstract
Small heat shock proteins (sHSPs) perform a fundamental role in protecting cells against a wide array of stresses but their biological function during viral infection remains unknown. Rice stripe virus (RSV) causes a severe disease of rice in Eastern Asia. OsHSP20 and its homologue (NbHSP20) were used as baits in yeast two-hybrid (YTH) assays to screen an RSV cDNA library and were found to interact with the viral RNA-dependent RNA polymerase (RdRp) of RSV. Interactions were confirmed by pull-down and BiFC assays. Further analysis showed that the N-terminus (residues 1–296) of the RdRp was crucial for the interaction between the HSP20s and viral RdRp and responsible for the alteration of the sub-cellular localization and distribution pattern of HSP20s in protoplasts of rice and epidermal cells of Nicotiana benthamiana. This is the first report that a plant virus or a viral protein alters the expression pattern or sub-cellular distribution of sHSPs.
Highlights
Plant heat shock proteins (HSPs) are stimulated in response to a wide array of stress conditions and perform a fundamental role in protecting plants against abiotic stresses[1,2,3]
Two published data sets with both Agilent and Affymetrix rice genome microarrays consistently showed that OsHSP20 accumulated in rice plants after Rice stripe virus (RSV) infection[20,39], suggesting that OsHSP20 might be involved in the host response to RSV infection
Organelle-targeted small heat shock protein (sHSP) are unique to plants and their diverse functions are thought to be associated with their sub-cellular localization[43] little is known about their distinct functions[41]
Summary
Plant heat shock proteins (HSPs) are stimulated in response to a wide array of stress conditions and perform a fundamental role in protecting plants against abiotic stresses[1,2,3]. Heat shock granules that appear in the cell cytoplasm under stress conditions are largely composed of sHSPs together with the partially unfolded RNA-binding proteins and associated mRNAs that they are protecting[9]. RSV vRNA4 encodes a disease-specific protein p4 that accumulates in both infected plant and insect cells[36]. RSV p2 can bind to OsSGS3, a rice host protein[32], PsbP, a 23 kDa oxygen-evolving complex protein of plants, has been shown to interact with p4, and its silencing resulted in more severe symptoms and the accumulation of viral RNAs37. In this study we investigated the interactions between sHSPs and RSV-encoded proteins and found that the expression and sub-cellular localization of a host small heat shock protein 20 (HSP20) was significantly affected by RSV infection and that this was caused by its interaction with the viral RdRp
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