Fig. 4

Schematic representation of the protocols used for scarp expression studies in the different hosts and expression of scarps under these conditions. Positive and negative detection (see Methods for details) of scarp2b and scarp5a transcripts in the different hosts are noted ‘-‘ or ‘+’, respectively. Protocol A (left column): A culture of S. citri in axenic medium was injected in insects, which then were fed on young periwinkles that became symptomatic within 3 weeks (leafhopper-infected plants LIP). S. citri extracted from LIP were then cultivated in axenic medium. Protocol B (right column): 5 months after inoculation, graft inoculated plants exhibiting symptoms (GIP) served as source of S. citri cultivated in axenic medium. After one passage, scarp2b transcripts were undetectable. After 10 passages, scarp2b transcripts could be detected, and spiroplasmas were microinjected to insects. The insects were fed on young periwinkles. Symptomatic periwinkles were used to graft a new batch of periwinkle plants, which developed symptoms (grafted plants second generation)