Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Biology

Supervisor

Dr. Aiming Wang

2nd Supervisor

Dr. Mark Bernards

Joint Supervisor

Abstract

Plant viruses have small and compact genomes whose coding capacity is not sufficient to fulfil the viral life cycle. Thus, they are largely dependent on the host by recruiting many host components such as proteins and membranes. Many efforts have been made towards understanding the role of host factors and recent progress has led to the identification and characterization of a number of important host factors recruited for plant virus replication. DEAD-box RNA helicases (RHs) have been shown to play multiple roles in RNA metabolism, including remodeling RNA structures and promoting RNA-protein association/dissociation. During viral replication, RHs are implicated in several key steps of the infection process, such as viral genome translation, unwinding double-stranded RNA intermediates, and maintaining viral gene integrity by suppression of viral RNA recombination. Here, we used Turnip mosaic virus (TuMV), a member of potyviruses, as a model virus to explore RHs' role in viral infection. Firstly, we screened Arabidopsis T-DNA insertion mutants corresponding to RHs and identified three Arabidopsis DEAD-box RNA helicases (AtRHs) that are associated with TuMV infection. We further characterized an Arabidopsis DEAD-box RNA helicase, PRH75, which is required for TuMV infection as downregulation of PRH75 in Arabidopsis impedes the viral infection. We also found that PRH75 interacts with several viral proteins including TuMV helicase CI, RNA-dependent RNA polymerase (RdRP) NIb and viral genome-linked protein VPg. In TuMV-infected cells, PRH75 colocalizes with the 6K2-induced viral replication complex (VRC) and viral dsRNA. The recruitment of PRH75 to the VRC is possibly through its interactions with viral replicase components CI, NIb and VPg. As an RNA helicase, PRH75 may assist in unwinding viral RNA duplexes during TuMV replication. Moreover, the work here also presents evidence demonstrating that the nuclear transport of TuMV viral proteins is mediated by Arabidopsis importin α. Taken together, these data suggest that PRH75 is an essential host factor required for TuMV infection.


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