Flavescence dorée phytoplasma has multiple ftsH genes differentially expressed in plants and insects. FTSH genes of Flavescence doree phytoplasma

Flavescence Dorée (FD) is a severe epidemic disease of grapevine caused by the FD phytoplasma (FDp) and transmitted by the leafhopper vector Scaphoideus titanus. The recent deciphering of the 647 kbp-long FDp genome highlighted the unusual number of genes encoding ATP dependent zinc proteases FtsH. Differences in virulence among isolates of ‘Candidatus Phytoplasma mali’ have recently been associated to variations in FtsH sequences. The aims of the present study were to predict the FtsH repertoire of FDp and the orientation of the various FtsH in the phytoplasma membrane, to measure the expression profile in different hosts and to develop a heterologous expression system to sustain future studies of their associated ATPase and proteolytic activities. Eight ftsH genes have been identified in the FDp genome. Their expression has been tested in plants and insects of a natural and an experimental pathosystems, resulting in host-dependent differential expression. Beside FtsH6 that appeared to be the original ortholog, the other seven gene copies clustered on a common distinct phylogenetic branch, in agreement with an intra genome duplication of ftsH. Only 2 of the 8 FtsH C-tails were predicted by the software Polyphobius to be extracellular therefore in direct contact with the host cellular content. The soluble part of three FtsH were expressed in E. coli and purified FtsH exhibited an ATPAse activity but their involvement in the degradation of host proteins is still hypothetic. These data raised the question of the involvement of FtsH in the adaptation to hosts, and in the pathogenicity of the FDp.