Immunodominant membrane protein (Imp) promotes the transmission of wheat blue dwarf (WBD) phytoplasma by directly interacting with α-tubulin in leafhoppers

Phytoplasmas are important plant pathogens that affect crops, bushes, and trees. Wheat blue dwarf (WBD) phytoplasma is transmitted by the leafhopper Psammotettix striatus, with infection resulting in severe losses in wheat yield in Northwest China. Immunodominant membrane protein (Imp) potentially plays a crucial role in phytoplasma transmission, although the mechanisms of WBD phytoplasma transmission has not yet been elucidated. In this study, the interaction between alpha-tubulin and Imp was confirmed by a split-ubiquitin membrane yeast two-hybrid assay, and co-immunoprecipitation (co-IP) assay. Co-expression of mNeonGreen-Imp and mScarlet-alpha-tubulin fusion proteins in the baculovirus expression vector system (BEVS) showed that Imp colocalizes with alpha-tubulin in the cytoplasm of Spodoptera frugiperda (Sf9) cells near the cell membrane. Suppression of alpha-tubulin transcription by RNA interference (RNAi) decreased the transmission efficiency of the WBD phytoplasma. Results of this study show that Imp employs alpha-tubulin to promote transmission of WBD phytoplasma via leafhopper. To our knowledge, this is the first report that describes the molecular interactions between the WBD phytoplasma and leafhopper. These results may help elucidate the mechanisms governing transmission of phytoplasma by its insect vector and provide a candidate target gene for controlling spread of WBD phytoplasma in the field using the RNAi approach.