Abstract
Broad bean wilt virus 2 (BBWV2) is an emerging virus in various economically important crops, especially pepper (Capsicum annuum L.), worldwide. Recently, the emergence of various BBWV2 strains that induce severe symptoms has increased damage to pepper crops. While the symptomatic variations among virus strains should be associated with differences in the transcriptomic reprogramming of host plants upon infection, underlying molecular mechanisms and associated genes are largely unknown. In the present study, we employed transcriptome analysis to identify responsible host factors for symptom enhancement in the BBWV2-pepper pathosystem using two distinct BBWV2 strains, PAP1 (a severe strain) and RP1 (a mild strain). Comparative analysis of the differentially expressed genes (DEGs) revealed that various genes associated with pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) and ethylene signaling were significantly upregulated upon infection with the severe PAP1 strain, but not with the mild RP1 strain. Indeed, hormone analysis revealed that ethylene emission was significantly increased in pepper plants infected with PAP1. These observations imply that the activation of the PTI-associated defense responses reinforce symptom formation during BBWV2 infection in a virus strain-specific manner.
Highlights
The symptom severity of crop diseases is closely related to productivity (Gaunt, 1995)
Using the chimeric viruses and amino acid substitution mutant viruses derived from pBBWV2-RP1 and pBBWV2-PAP1, we demonstrated that movement protein (MP) is the viral strain-specific factor that determines symptom severity in broad bean wilt virus 2 (BBWV2) (Seo et al, 2017)
The results showed no significant difference in viral RNA accumulation between the two BBWV2 strains (Figure 2A), suggesting that the symptomatic difference between the two BBWV2 strains was not due to differences in virus accumulation levels
Summary
The symptom severity of crop diseases is closely related to productivity (Gaunt, 1995). BBWV2 Infection Activates PTI development, physiology, and metabolism (Seo et al, 2018) In this regard, the identification of crucial host genes associated with symptomatic variation and their underlying molecular mechanisms can provide new insights into molecular plant physiological phenomena as well as symptom development. While more than 100 viruses infect pepper plants worldwide (Kenyon et al, 2014), broad bean wilt virus 2 (BBWV2; genus Fabavirus, family Secoviridae) is an emerging virus in many global areas (Kwak et al, 2013a,b; Ferriol et al, 2014). Each RNA segment encodes a single open reading frame (ORF) that translates into a large polyprotein precursor. RNA2 expresses the following three mature proteins: movement protein (MP), large coat protein (LCP), and small coat protein (SCP; Ferrer et al, 2011)
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