Aphid transmission of nanoviruses

Abstract

The genus Nanovirus consists of plant viruses that predominantly infect legumes leading to devastating crop losses. Nanoviruses are transmitted by various aphid species. The transmission occurs in a circulative nonpropagative manner. It was long suspected that a virus‐encoded helper factor would be needed for successful transmission by aphids. Recently, a helper factor was identified as the nanovirus‐encoded nuclear shuttle protein (NSP). The mode of action of NSP is currently unknown in contrast to helper factors from other plant viruses that, for example, facilitate binding of virus particles to receptors within the aphids' stylets. In this review, we are summarizing the current knowledge about nanovirus–aphid vector interactions.

Nanovirus Disease Complexes: An Emerging Threat in the Modern Era

“…FBNSV follows a route similar to that of the geminiviruses but distinct from that of the luteoviruses, as demonstrated by transportation through cells of the anterior midgut and principal salivary gland. A large number of virus particles enter each susceptible cell to keep distinct genome segments together (Di Mattia et al, 2020;Gaafar and Ziebell, 2020). Previously, similar studies were conducted to track the BBTV (genus Babuvirus) within its aphid vector by monitoring the coat protein (Bressan and Watanabe, 2011;Watanabe and Bressan, 2013;Watanabe et al, 2016).…”

“…The virions that were produced within the plants inoculated with the seven components, excluding DNA-N, abolished the aphid transmission as well when a mutated NSP with a 13-amino acid tag at the carboxyl-terminus was introduced but restored aphid transmission with the introduction of DNA-N of another nanovirus PNYDV (Grigoras et al, 2018), which reinforced the mandatory role of NSP in viral accumulation into the gut cells of the aphid. Co-localization of NSP and coat protein with other viral genome segments, suggest that NSPvirus particle complexes are the viral form that cycles within the aphid body (Di Mattia et al, 2020;Gaafar and Ziebell, 2020). Vector transmission is the major and best-documented mode of transmission of plant viruses, but many gaps i.e., purpose of self interactions between NSPs during translocation, impact of the changes in virus formulas on virus transmission etc., need to be addressed.…”

RNAi technology for management of banana bunchy top disease

“…It was recently demonstrated that the success of nanovirus-vector interaction depends on a nonstructural helper component that is shown to be mandatory for viral accumulation within the gut cells (Di Mattia et al, 2020). The viral protein nuclear shuttle protein (NSP) encoded by DNA-N has been identified as a helper factor essential for aphid viral transmission of nanoviruses (Gaafar & Ziebell, 2019;Grigoras et al, 2018). Di Mattia et al (2020) demonstrated the colocalization of both the NSP and CP with the viral genome segments.…”

“…This suggests that NSP–virus particle complexes are the viral form that cycles within the aphid body. An exclusion of DNA‐N from the eight components of a nanovirus, Faba bean necrotic stunt virus (FBNSV), genome prevented transmission of the virus by an aphid (Gaafar & Ziebell, 2019). Furthermore, altering the nuclear shuttle protein of FBNSV, by including nonfunctional proteins to the carboxy‐terminus led to an infectious but nontransmissible virus (Grigoras et al., 2018).…”

“…Furthermore, altering the nuclear shuttle protein of FBNSV, by including nonfunctional proteins to the carboxy‐terminus led to an infectious but nontransmissible virus (Grigoras et al., 2018). This helper factor makes it possible for the virus to bind receptors within the aphid's stylet to facilitate transmission (Brault et al., 2010; Gaafar & Ziebell, 2019). The stylets of aphids have a unique ability to bind, retain, and release the virus into plant phloem during feeding (Deshoux et al., 2020).…”