Interaction between plant responses and transmission of TuMV by Myzus persicae

BGPI : équipe 2Many viruses are transmitted by aphids in a non-circulative manner. This indicates that when aphids feed on an infected plant, the transmitted virus particles attach within seconds to the stylets, and are transported in them to a new host plant. This is the case of the Caulimovirus Cauliflower mosaic virus (CaMV), which follows the molecular strategy called “transmission helper component” for transmission. Its viral helper component, protein P2, intervenes by creating the molecular link between virus particles and stylets. In presence of aphid vectors, CaMV forms transmissible P2-virus complexes in the cell. This phenomenon, called "Transmission Activation(TA)", boosts CaMV transmission and depends on CaMV interfering with aphid-plant responses. We are interested in the transmission of the Potyvirus Turnip mosaic virus (TuMV), another non circulative virus using the transmission helper component strategy with its viral protein Helper Component Protease (HC-Pro). We wanted to determine whether this virus also uses TA. Aphid transmission tests with Myzus persicae were carried out using infected protoplasts as virus source that were incubated with different reagents, mimicking plant defense responses, before the transmission tests. The results showed that a blocker of calcium signaling, LaCl3, reduced transmission while the reactive oxygen species (ROS), H2O2, activated it. This suggests that different plant defense responses modify the cellular environment in which HC-Pro is located, induce TA of TuMV and therefore its acquisition by aphids. Moreover, western blotting showedthat LaCl3 inhibited and H2O2 induced formation of intermolecular cysteine bonds linking HC-Prooligomers. Taken together, our results demonstrate that TuMV transmission can be activated, that calcium signaling and ROS are involved in it and that it correlates with oxidation of HC-Pro. Thus, TuMV is a second example for the TA phenomenon, and a model of Potyvirus transmission