Investigation over the life cycle of ST1-C the endosymbiont of Scaphoideus titanus

Scaphoideus titanus Ball (Hemiptera Cicadellidae) is a phloem-feeder leafhopper vector of ‘Candidatus Phytoplasma vitis’, the\r\nphytoplasma responsible of “flavescence dorée” (FD), a grape yellows afflicting several wine production areas in Europe. Natural\r\nsymbionts of the leafhopper for symbiotic control of FD transmission could be used. Previous work showed the presence of a\r\nCFB bacterium, ‘Candidatus Cardinium sp.’ (named ST1-C) in several body districts of S. titanus. Our work was aimed to investigate\r\nthe life cycle of ST1-C endosymbiont inside and outside of insect body. We fed S. titanus individuals on artificial media\r\nand tested insects and diets after the treatment for the presence of the ST1-C endosymbiont by qualitative and quantitative PCR,\r\nshowing the release of the bacterium during feeding. We also performed fluorescent in situ hybridization on the sugar solutions\r\nafter insect feeding, detecting ST1-C cells that confirmed its release into the medium. We tested by ST1-C-specific PCR DNA\r\nextracted from small areas of grape leaves exposed to S. titanus, identifying the bacterium in the majority of pierced leaves. Our\r\nexperiments suggest that the ST1-C endosymbiont can undergo a horizontal transmission and have a complex life cycle possibly\r\ninvolving more than one host.