AV2 protein of tomato leaf curl Palampur virus promotes systemic necrosis in Nicotiana benthamiana and interacts with host Catalase2

Poonam Roshan,Vipin Hallan,Surender Kumar,Rituraj Purohit,Aditya Kulshreshtha

doi:10.1038/s41598-018-19292-3

Abstract

Tomato leaf curl Palampur virus (ToLCPalV) is a whitefly-transmitted, bipartite begomovirus. Here, we demonstrated that ectopic expression of AV2 from a Potato virus X (PVX)-based vector accelerated systemic necrosis and reactive oxygen species (ROS) accumulation in Nicotiana benthamiana. Furthermore, 10 amino acids from N-terminal region of AV2 were found to be associated with the systemic necrosis symptom/phenotype. Mutational studies of ToLCPalV infectious clones lacking the AV2 revealed that AV2 is essential for the systemic movement of DNA-A, symptom severity and viral DNA accumulation. In a yeast two-hybrid assay, Catalase2 (Cat2) was found to associate with AV2 protein. Further, silencing of Cat2 resulted in appearance of necrotic lesions on N. benthamiana and these plants were highly susceptible to ToLCPalV infection in comparison to control plants. Infection ToLCPalV on Solanum lycopersicum resulted in downregulation of Cat2 transcripts, followed by accumulation of ROS and stress marker transcripts. The AV2 protein also suppressed virus-induced gene silencing (VIGS) of the Phytoene desaturase (PDS) gene. Our results show that AV2 is essential for the pathogenicity, systemic movement and suppression of gene silencing in the host. Altogether, our findings suggest that interactions between AV2 and Cat2 might play a crucial role in the establishment of ToLCPalV infection.

Highlights

Viruses are biotrophic pathogens that utilize the cellular machinery of a host for successful invasion
We selected 15 regenerated transgenic plants overexpressing the AV2 protein after hygromycin selection; T0 plants were grown under greenhouse conditions, and the presence of a transgene was confirmed by PCR amplification using gene-specific primers
These results suggest that stable overexpression of the AV2 protein is detrimental to the normal growth of this plant

Summary

Introduction

Viruses are biotrophic pathogens that utilize the cellular machinery of a host for successful invasion. An incompatible interaction of a virulent avr protein (effector) with the R protein (plant receptor) can lead to the development of disease resistance against the invading pathogen[1], triggering biochemical and physiological changes that are accompanied by the hypersensitive response and/or systemic acquired resistance These cellular events lead to regulation/activation of defence-related plant genes, which results in cessation of viral replication at sites of entry or virus movement[1,2,3]. The DNA-B component comprises the BV1 and BC1 ORFs on the virion sense and antisense strands, respectively These ORFs encode the coat protein (AV1), precoat protein (AV2), replication initiator protein (AC1), transcription activator protein (AC2), replication enhancer protein (AC3), AC4 protein, nuclear shuttle protein (BV1) and movement protein (BC1). AV2 was found to suppress virus-induced gene silencing by the host

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Results

Conclusion