Analysis of Pathogenicity and Virulence Factors of Ageratum leaf curl Sichuan virus.

Ling Qing,Pengbai Li,Hussein Ghanem,Zhou Jia,Hongyan Ren,Chenchen Jing,Mingjun Li,Gentu Wu

doi:10.3389/fpls.2020.527787

Abstract

Ageratum leaf curl Sichuan virus (ALCScV) is a novel monopartite begomovirus, which was identified from Ageratum conyzoides plants in Sichuan Province, China. In this study, we showed that ALCScV can induce typical dwarf and downward leaf-curling symptoms in Ageratum conyzoides, Helianthus annuus, and Nicotiana benthamiana plants and that the noncognate betasatellite can enhance disease symptoms and increase viral accumulation. Expression of the ALCScV-encoded V2, C1, and C4 proteins through a Potato virus X (PVX) vector caused severe symptoms in N. benthamiana. Further study revealed no symptoms in N. benthamiana plants inoculated with infectious ALCScV clones lacking the C4 protein and that the relative viral DNA accumulation levels significantly decreased when compared with ALCScV-inoculated plants. Thus, our mutational analyses demonstrated that C4 is a pathogenicity determinant that plays key roles in symptom formation and virus accumulation. Furthermore, we also demonstrated that the second glycine of C4 was critical for ALCScV pathogenicity.

Highlights

Geminiviruses comprise a group of plant viruses with circular, single-stranded DNA genomes (Harrison, 1985)
At 14 days post-inoculation, leaf curling and shrinking started to appear on Ageratum conyzoides, Helianthus annuus and N. benthamiana plants inoculated with Ageratum leaf curl Sichuan virus (ALCScV) (Figures 1A–C)
At 21 dpi, the symptoms became more severe, with typical dwarf, enation, and downward leaf curling symptoms observed in N. benthamiana plants inoculated with ALCScV and no symptoms observed in mock-inoculated N. benthamiana plants (Figure S1)

Summary

Introduction

Geminiviruses comprise a group of plant viruses with circular, single-stranded DNA genomes (Harrison, 1985). Based on their transmission by insect vectors, genome structures, and host ranges, geminiviruses have been classified into nine genera (Begomovirus, Mastrevirus, Grablovirus, Capulavirus, Eragrovirus, Curtovirus, Becurtovirus, Topocuvirus, and Turncurtovirus) (Fauquet et al, 2008; Varsani et al, 2014; Varsani et al, 2017). Depending on the genomic component, begomoviruses can be classified into those with a bipartite genome or a monopartite genome (Harrison and Robinson, 1999). Bipartite begomovirus genomes are composed of two genomic components (DNA-A and DNA-B) (Briddon et al, 2010), whereas the monopartite begomoviruses only contain one genomic component (DNA-A) (Fondong, 2013). Previous findings from some studies have shown that most monopartite begomoviruses and a few bipartite begomoviruses are associated with satellite molecules (alphasatellites or betasatellites)

Methods

Results

Conclusion