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Cloning and Characterization of the Antigenic Membrane Protein (Amp) Gene and In Situ Detection of Amp from Malformed Flowers Infected with Japanese Hydrangea Phyllody Phytoplasma

First, second, third, fourth, sixth, seventh, eighth, and ninth authors: Laboratory of Plant Pathology, Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan; and fifth author: Laboratory of Fungal Plant Pathology, Department of Agricultural Biology, College of Agriculture and Life Sciences, Kyungpook National University, 1370 Sangyeok3-dong, Buk-gu, Daegu, 702-701 Korea.

A Japanese hydrangea phyllody (JHP) disease found throughout Japan causes economic damage to the horticultural industry. JHP phytoplasma-infected Japanese hydrangea plants show several disease symptoms involved in floral malformations, such as virescence, phyllody and proliferation. Here, we cloned and characterized the antigenic membrane protein (Amp) gene homolog from the JHP phytoplasma (JHP-amp), expressed the JHP-Amp protein in Escherichia coli cells, and then obtained an antibody against JHP-Amp. The antibody against JHP-Amp had no cross-reactions with the antibody against the Amp protein from a closely related onion yellows phytoplasma. This serologic specificity is probably due to the high diversity of the hydrophilic domains in the Amp proteins. The in situ detection of the JHP-Amp protein revealed that the JHP phytoplasma was localized to the phloem tissues in the malformed flower. This study shows that the JHP-Amp protein is indeed a membrane protein, which is expressed at detectable level in the JHP phytoplasma-infected hydrangea.

Additional keywords:immunodominant membrane protein, mollicutes.