Fitoplasmi e cicadellidi vettori: interazioni molecolari e specificita? di trasmissione

"Phytoplasmas and leafhopper vectors: molecular interactions and transmission specificity Insect-borne plant pathogens are viruses, bacteria and mollicutes (spiroplasmas and phytoplasmas) as well as some fungi. Vectors of these pathogens are mainly pierce-sucking insects (orders Hemiptera and Thysanoptera) and some species of Coleoptera. Phytoplasmas are wall-less bacteria, inhabiting phloem elements of infected plants. They cause hundreds of plant diseases with huge economic losses. Phytoplasmas are transmitted in a persistent propagative manner by some species of phloem-sucker hemipteran insects, largely belonging to Deltocephalinae subfamily. The control of phytoplasma diseases is based on containment of vector populations, mainly through spraying of insecticides. Here, the molecular recognitions between pathogen and vector are explored. These mechanisms allow the overcoming of the two main barriers encountered by phytoplasma cells during the colonization of the vector body: penetration of the gut epithelium and entry into the salivary glands. In particular, we focused on studies on the onion yellows (OY) and chrysanthemum yellows (CY) strains of 'Candidatus Phytoplasma asteris' and on the grapevine Flavescence dore?e (FD) phytoplasma. Phytoplasma membrane proteins are in direct contact with host cells and are the molecular partners mainly involved in the interaction with vectors. The immunodominant membrane proteins (Amp and Imp) and the variable membrane protein (VmpA) are the main protagonists of these relationships with different species of leafhopper vectors. The activation of the immune response in the insect following phytoplasma infection is also briefly treated. A gap of knowledge on pathogen/vector relationships still remains and needs to be filled, especially to develop new and more sustainable control tools to cope with phytoplasma diseases."