Abstract
Cucurbit chlorotic yellows virus (CCYV) is a cucurbit-infecting crinivirus. RNA silencing can be initiated as a plant defense against viruses. Viruses encode various RNA silencing suppressors to counteract antiviral silencing. P22 protein encoded by RNA1 of CCYV is a silencing suppressor, but its mechanism of action remains unclear. In this study, the cucumber ribosomal-like protein CsRPS21 was found to interact with P22 protein in vitro and in vivo. A conserved CsRPS21 domain was indispensable for its nuclear localization and interaction with P22. Transient expression of CsRPS21 in Nicotiana benthamiana leaves interfered with P22 accumulation and inhibited P22 silencing suppressor activity. CsRPS21 expression in N. benthamiana protoplasts inhibited CCYV accumulation. Increasing numbers of ribosomal proteins are being found to be involved in viral infections of plants. We identified a P22-interacting ribosomal protein, CsRPS21, and uncovered its role in early viral replication and silencing suppressor activity. Our study increases knowledge of the function of ribosomal proteins during viral infection.
Highlights
The members of the genus Crinivirus cause significant yield and quality losses in many cucurbit species (Kreuze et al, 2005; Navas-Castillo et al, 2011)
To determine if the interaction influenced the localization of CsRPS21 and P22, Yellow fluorescent protein (YFP)-CsRPS21 and YFP-P22 were transiently expressed in N. benthamiana leaves
In our study we found that CsRPS21 interacted with chlorotic yellows virus (CCYV) P22 and negatively regulated CCYV P22 accumulaiton and silencing suppressor activity, and early viral accumulaiton
Summary
The members of the genus Crinivirus cause significant yield and quality losses in many cucurbit species (Kreuze et al, 2005; Navas-Castillo et al, 2011). Like most members of the genus Crinivirus, cucurbit chlorotic yellows virus (CCYV) has a bipartite genome. In addition to CCYV P22, P22 proteins of tomato chlorosis virus (ToCV) and sweet potato chlorotic stunt virus (SPCSV), P23 of lettuce chlorosis virus (LCV), and P25 of cucurbit yellow stunting disorder virus (CYSDV) have been identified as RNA silencing suppressors (Kreuze et al, 2005; Canizares et al, 2008; Kataya et al, 2009; Kubota and Ng, 2016; Orfanidou et al, 2019; Salavert et al, 2020)
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