Abstract
Dissecting the complex molecular interplay between the host plant and invading virus improves our understanding of the mechanisms underlying viral pathogenesis. In this study, immunoprecipitation together with the mass spectrometry analysis revealed that the heat shock protein 70 (Hsp70) family homolog, Hsc70-2, was co-purified with beet black scorch virus (BBSV) replication protein p23 and coat protein (CP), respectively. Further experiments demonstrated that Hsc70-2 interacts directly with both p23 and CP, whereas there is no interaction between p23 and CP. Hsc70-2 expression is induced slightly during BBSV infection of Nicotiana benthamiana, and overexpression of Hsc70-2 promotes BBSV accumulation, while knockdown of Hsc70-2 in N. benthamiana leads to drastic reduction of BBSV accumulation. Infection experiments revealed that CP negatively regulates BBSV replication, which can be mitigated by overexpression of Hsc70-2. Further experiments indicate that CP impairs the interaction between Hsc70-2 and p23 in a dose-dependent manner. Altogether, we provide evidence that besides specific functions of Hsp70 family proteins in certain aspects of viral infection, they can serve as a mediator for the orchestration of virus infection by interacting with different viral components. Our results provide new insight into the role of Hsp70 family proteins in virus infection.
Highlights
Beet black scorch virus (BBSV) is a positive-strand RNA virus belonging to the genus Betanecrovirus in the family Tombusviridae[1]
Chkuaseli et al reported that deletion of coat protein (CP) in Tobacco necrosis virus-D (TNV-D), a member of the genus Betanecrovirus, leads to the increased viral RNA accumulation[16], suggesting that CP may function in modulating the viral replication
Our results showed that Hsc[70-2] is essential for beet black scorch virus (BBSV) replication through interaction with the p23, whereas CP disrupts the interaction between Hsc[70-2] and p23 in a dose-dependent manner, and overexpression of Hsc[70-2] mitigates the negative effect of CP on BBSV replication
Summary
Beet black scorch virus (BBSV) is a positive-strand RNA virus belonging to the genus Betanecrovirus in the family Tombusviridae[1]. Because host factors involved in viral replication represent potential targets for virus control, identification and functional characterization of their roles is one of the hot topics in virus research Both auxiliary replicase protein and RNA-dependent RNA polymerase (RdRp) are the key components of VRC and have potential to be baits for identifying host interactors. Despite the fundamental role in protein quality control, Hsp70s are tightly associated with multiple aspects of viral infection cycle, such as cell entry, virion assembly and disassembly, genome replication and viral gene expression[27,30,31,32]. Recent studies indicated that Hsc[70] is co-opted by CNV to functions in several aspects of the viral infection cycle, including the positive regulation of viral RNA accumulation, virus particle assembly and disassembly, and targeting of CP to the chloroplasts[27,39]. These data suggest a new role of Hsc[70-2] in regulating BBSV replication through interaction with different viral components
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