ISHS Acta Horticulturae 550: XVIII International Symposium on Virus and Virus-like Diseases of Temperate Fruit Crops - Top Fruit Diseases
MOLECULAR VARIATION IN IMMUNODOMINANT MEMBRANE PROTEINS FROM PHYTOPLASMAS |
| Authors: | D.J. Barbara, A. Morton, M.F. Clark, D.L. Davies |
| Keywords: | Aster yellows, Clover phyllody, Pear decline, European stone fruit yellows. |
| Abstract:
The immunodominant membrane proteins (Imps) associated with phytoplasmas may be important in host-pathogen interactions. Here we compare some properties of Imps (and the genomic locations of the genes encoding them) from seven phytoplasmas placed taxonomically into four distinct rRNA clades. The sequences of three of these Imps are published; the other four genes were newly cloned and characterised for this work. Three major types of Imp were found, with combinations of one or two cleavable and non-cleavable trans-membrane regions, but all would present a single major hydrophilic domain on the outside of the phytoplasma cell. This major domain was very similar in size for Imps from phytoplasmas in two clades but much more divergent for the other two clades. Similarly there were many more sequence differences for two examples in the aster yellows clade than were seen in this domain for three phytoplasmas in the apple proliferation clade. The imp genes appeared to be in the same genomic location for the sweet potato witches' broom and apple proliferation clades but in two different positions for the aster yellows and western X clades. The possible significance of the variation between these gene products is discussed. | |
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