Abstract: Abstract：【Objective】The aim of the experiment is to elucidate the molecular mechanism of vector-pathogen-host plant relationships.【Method】Using primers Imp1051/Imp2265 designated by conserved regions of immundominant membrane protein gene from phytoplasmas amplify DNA samples extracted from infected wheats and periwinkles; The amplified fragment is analysed for open reading frame,homology matrix and phylogentic tree; Encoding protein is anlysised for transmembrane region, hydrophilic and hydrophobic region and leader signal sequence.【Result】A 1.0kb DNA fragment was amplified by polymerase chain reaction in DNA samples extracted from infected wheats and periwinkles but not in those extranted from healthy plants. It was showed that immundominant membrane protein gene from wheat blue dwarf(WBD) phytoplasma was 495 bp in length, encoding a predicted protein of 164 amino acids. Homology analysis of sequence from WBD and 10 phytoplasmas showed that immundominant membrane protein gene of WBD phytoplasma was closely related to those of clover phyllody(CP) phytoplasma, with homology rate of nucleotide and amino acids sequences, 98.5% and 95.1%. Prediction of protein structure showed the immunodominant membrane proteins from WBD phytoplasma possess a N-terminal hydrophobic transmembrane regions with export leader signal sequence, a C-terminal hydrophobic transmembrane anchor, and a central hydrophilic region, possibly external to the phytoplasma cell.【Conclusion】Immundominant membrane protein of WBD phytoplasma belong to the same type with those of CP, aster yellow(AY), onion yellow(OY) and paulownia witches’-broom(PaWB) phytoplasmas.

Key words: wheat blue dwarf phytoplasma, immunodominant membrane protein, homology, structure of protein