Flavescence Dorée (FD) is an epidemic disease impacting grapevines, associated with Flavescence Dorée phytoplasma (FDp), a small wall-less bacteria living in and feeding from the plant phloem. In the vineyards, FD is mainly transmitted by a leafhopper called Scaphoideus titanus which also feeds on plant phloem. The recent sequencing of the complete genome of FDp strain CH confirmed the presence of cellular mechanisms associated to phytoplasmas and unraveled a list of potential effectors, with the majority annotated as hypothetical proteins. Effectors are proteins secreted by pathogens for the purpose of targeting plant physiology processes or to disrupt plant immune mechanisms, to allow colonization and optimal fitness of the pathogen. They are key proteins to understand the molecular mechanisms in pathogen-host interaction, and therefore how or which molecular elements make grapevine susceptible to FDp. The present work aims to start characterizing FDp effector candidates. Transcriptional profiles of the latter were analyzed in plant and insect hosts. One putative effector gene revealed to be more expressed in grapevine than insect vectors. It was therefore selected for parameters study of in vivo expression in Escherichia coli and for other cloning constructions, in preparation of future experiments.