In Vitro Acquisition of Specific Small Interfering RNAs Inhibits the Expression of Some Target Genes in the Plant Ectoparasite Xiphinema index

Xiphinema index is an important plant parasitic nematode that induces direct damages and specifically transmits the Grapevine fanleaf virus, which is particularly harmful for grapevines. Genomic resources of this nematode species are still limited and no functional gene validation technology is available. RNA interference (RNAi) is a powerful technology to study gene function and here we describe the application of RNAi on several genes in X. index. Soaking the nematodes for 48 h in a suspension containing specific small interfering RNAs resulted in a partial inhibition of the accumulation of some targeted mRNA. However, low reproducible silencing efficiency was observed which could arise from X. index silencing pathway deficiencies. Indeed, essential accustomed proteins for these pathways were not found in the X. index proteome predicted from transcriptomic data. The most reproducible silencing effect was obtained when targeting the piccolo gene potentially involved in endo-exocytosis of synaptic molecules. This represents the first report of gene silencing in a nematode belonging to the Longidoridae family

Impact of Mutations in Arabidopsis thaliana Metabolic Pathways on Polerovirus Accumulation, Aphid Performance, and Feeding Behavior

During the process of virus acquisition by aphids, plants respond to both the virus and the aphids by mobilizing different metabolic pathways. It is conceivable that the plant metabolic responses to both aggressors may be conducive to virus acquisition. To address this question, we analyze the accumulation of the phloem-limited poleroviru

Nanobody-mediated resistance to grapevine fanleaf virus in plants

Since their discovery, single-domain antigen-binding fragments of camelid-derived heavy-chain-only antibodies, also known as nanobodies (Nbs), have proven to be of outstanding interest as therapeutics against human diseases and pathogens including viruses, but their use against phytopathogens remains limited. Many plant viruses including Grapevine fanleaf virus (GFLV), a nematode-transmitted icosahedral virus and causal agent of fanleaf degenerative disease, have worldwide distribution and huge burden on crop yields representing billions of US dollars of losses annually, yet solutions to combat these viruses are often limited or inefficient. Here, we identified a Nb specific to GFLV that confers strong resistance to GFLV upon stable expression in the model plant Nicotiana benthamiana and also in grapevine rootstock, the natural host of the virus. We showed that resistance was effective against a broad range of GFLV isolates independently of the inoculation method including upon nematode transmission but not against its close relative, Arabis mosaic virus. We also demonstrated that virus neutralization occurs at an early step of the virus life cycle, prior to cell-to-cell movement. Our findings will not only be instrumental to confer resistance to GFLV in grapevine, but more generally they pave the way for the generation of novel antiviral strategies in plants based on Nbs