Résumé
Increasing evidence suggests that viruses can manipulate host plant phenotypes and vector behaviors in ways that are conducive to their transmission. These manipulations of vector–host interactions can occur through i) virus effects on host cues that mediate vector orientation, feeding, and dispersal behaviors; and ii) direct (post-acquisition) effects of plant viruses on viruliferous vector behavior; both modifying the probability of virus transmission. However, to date, the underlying molecular mechanisms are largely unknown. Recent analyses suggest a potential implication of the plant RNA silencing mechanism and its products, the virus-derived small interfering (si)RNA (visi-RNA), in host and vector manipulations. In this study, we tested whether the Dicer-like (DCL) proteins play a role in turnip yellows virus (TuYV) effects on Arabidopsis and its aphid vector Myzus persicae. For this, we compared TuYV infection of Arabidopsis wild-type and dcl mutants. TuYV accumulation and symptoms were stronger on the dcl2/4 and dcl2/3/4 mutant lines than on other dcl lines or Col-0, while the transmission was reduced. Altered aphid probing and feeding behaviors (recorded by electrical penetration graph technique) could only partly explain the lower TuYV transmission rates on the two mutant lines, suggesting that other mechanisms are involved. TuYV-infected plants accumulate large quantities of phloem-mobile visi-RNAs that are acquired by aphids and could potentially modify aphid genes’ expression and behaviors. After three days of acquisition feeding on TuYV-infected dcl mutant lines, aphids exhibited altered inoculation feeding behavior on healthy recipient Col-0, highlighting possible post-acquisition effects. Altogether, our results indicate that DCL proteins play a role in the expression of host-plant phenotype with important consequences on aphid feeding behavior and virus transmission, and visi-RNAs could be involved in direct virus effects on aphid vector, which still need to be characterized.