Plant Arbovirus Mobilizes a Vector Salivary Protein to Initiate Plant Infection

Abstract

Plant arboviruses rely heavily on insects’ feeding activities for successful transmission. Insect salivary proteins have been suggested to be essential for successful viral infection, but their exact mechanisms are largely unknown. In this study, we reveal that salivary factors from Laodelphax striatellus are necessary for infection of Rice stripe virus (RSV) in plants. A salivary carbonic anhydrase (LssaCA) is identified as an essential factor in promoting RSV infection. LssaCA interacts with a rice thaumatin-like protein (OsTLP) that has endo-β-1,3-glucanase activity and can degrade callose in plants. RSV infection induces callose deposition, which can be reversed by LssaCA. Furthermore, LssaCA directly binds to the RSV nucleocapsid protein (NP) in salivary glands, and the LssaCA-RSV NP complex still binds OsTLP and further increases its glucanase activity. This study provides new insights into the tripartite virus-insect vector-plant interaction, which is relevant to many agriculturally important plant arboviruses whose transmission is facilitated by insect salivary proteins.