Asaia, a transformable bacterium, associated with Scaphoideus titanus, the vector of "flavescence dor\'ee"

A recent survey on the microflora associated with the leafhopper Scaphoideus titanus Ball (Hemiptera Cicadellidae), the vector of “flavescence dorée” (FD), showed the presence of bacteria belonging to the genus Asaia. These bacteria are symbionts of insects of the genus Anopheles, malarial mosquito vectors. We focused on the association between Asaia sp. and S. titanus with the aim to evaluate a possible role of this microorganism as a symbiotic control agent. After development of artificial feeding systems for S. titanus, quantitative PCR on insects or feeds DNA was performed with specific primers. Results underlined that Asaia sp. was dominant in the insect microflora. A strain of Asaia expressing a green fluorescent protein was used to perform recolonization of the body of S. titanus, showing the colonization by the bacterium of salivary glands, guts, female and male reproductive organs of the insect. In situ hybridization with specific probes was performed on insect dissections, confirming the presence of the bacterium in spermatic bundles and in Malpighian tubules. Easy cultivability, dominance within the bacterial population in the insect body, cryogenic preservability and easiness for genetic manipulation demonstrated by the overall data make Asaia sp. an optimal candidate for carrying factors for FD control.