Molecular Plant Pathology On-Line [http://www.bspp.org.uk/mppol/] 1997/0623gayler

The distribution of elicitin-like gene sequences in relation to elicitin protein secretion within the class Oomycetes

K R Gayler, K M Popa, D M Maksel, DL Ebert and B R Grant

Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria, 3052, Australia

Corresponding Author:

K R Gayler, Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria, 3052, Australia
e-mail: ken@biochemistry.unimelb.edu.au

The distribution of elicitin-like gene sequences and the capacity of particular species to secrete biologically active elicitins has been determined within and between genera of the Oomycetes. Species from five families were analysed for elicitins equivalent to those secreted by Phytophthora species (Kamoun, S., Young, M., Forster, H., Coffey, M., and Tyler, B. 1994. Applied Environmental Microbiology 60,1593-1598). Biologically active elicitin proteins were detected by bioassay and elicitin-like gene sequences analysed on Southern blotted genomic DNA using fragments of the coding region of elicitin genes from both Phytophthora and Pythium species. Despite the almost ubiquitous distribution of elicitin secretion within the genus Phytophthora, secretion of these proteins by species from outside of this genus was restricted to a relatively few species and all from the genus Pythium. All species which in liquid culture secreted protein active in the specific elicitin bioassay, contained small families of elicitin-like gene sequences and no such sequences were found elsewhere. Distribution of the elicitin-like gene sequences was compared with previously established phylogenetic relationships between the Oomycete families. It was concluded that elicitin gene distribution provides further evidence subdividing Pythium species into two potential genera.