RNA-dependent RNA polymerase (NIb) of the potyviruses is an avirulence factor for the broad-spectrum resistance gene Pvr4 in Capsicum annuum cv. CM334.

Saet-Byul Kim,Doil Choi,Hye-Young Lee,Seungyeon Seo,Joo Hyun Lee,Mark Gijzen

doi:10.1371/journal.pone.0119639

Abstract

Potyviruses are one of the most destructive viral pathogens of Solanaceae plants. In Capsicum annuum landrace CM334, a broad-spectrum gene, Pvr4 is known to be involved in resistance against multiple potyviruses, including Pepper mottle virus (PepMoV), Pepper severe mosaic virus (PepSMV), and Potato virus Y (PVY). However, a potyvirus avirulence factor against Pvr4 has not been identified. To identify the avirulence factor corresponding to Pvr4 in potyviruses, we performed Agrobacterium-mediated transient expressions of potyvirus protein coding regions in potyvirus-resistant (Pvr4) and -susceptible (pvr4) pepper plants. Hypersensitive response (HR) was observed only when a RNA-dependent RNA polymerase (NIb) of PepMoV, PepSMV, or PVY was expressed in Pvr4-bearing pepper leaves in a genotype-specific manner. In contrast, HR was not observed when the NIb of Tobacco etch virus (TEV), a virulent potyvirus, was expressed in Pvr4-bearing pepper leaves. Our results clearly demonstrate that NIbs of PepMoV, PepSMV, and PVY serve as avirulence factors for Pvr4 in pepper plants.

Highlights

Potyviruses belong to the family Potyviridae which represents the largest plant viruses, and severely affect the production of economically important crops
Lower values (ELSIA value < 0.2) which were detected with CM334, F1 hybrid and the resistant homozygotic F2 lines represented that pepper mottle virus (PepMoV) replication was limited in those peppers
ECW, Jupiter and the susceptible homozygotic F2 (SS) lines showed higher values (ELSIA value > 0.4) (Fig. 1B). These results indicated that populations derived from a cross between CM334 (Pvr4)-harboring plants successfully repressed the growth of PepMoV virus and that resistance phenotypes of pepper plants against PepMoV co-segregated with their genotypes

Summary

Introduction

Potyviruses belong to the family Potyviridae which represents the largest plant viruses, and severely affect the production of economically important crops. Several members of the genus Potyvirus including pepper mottle virus (PepMoV), pepper severe mosaic virus (PepSMV), potato virus Y (PVY) and tobacco etch virus (TEV) have a wide range of hosts such as potato, pepper, and tomato in Solanaceae plants [1]. NIb Is an Avirulence Factor of Pvr in Pepper translated from a 2+ frameshift in the P3 coding region [2]. These polyproteins are cleaved by viral proteases subsequently generating eleven mature proteins [3]

Methods

Results

Conclusion