Abstract:

Proteinaceous secretions from the oesophageal glands of plant-parasitic nematodes have crucial roles in nematode parasitism of plants, of which cellulases are among the best characterized. The full length cDNA sequence of a novel β-1, 4-endoglucanase gene from Radopholus similis was obtained by RT-PCR and RACE, named RS-eng-1 (GenBank: EU414839). It consisted of 1 630 bp in length, with a 1 404 bp ORF encoding a 467 amino acid protein. The putative protein, with the-oretical molecular weight 48.22 kD and pI 6.04, was classified as a member of glycosyl hydrolase family 5. Sequence analysis showed that it had a 22 amino acid signal sequence at N terminal and a bacterial type cellulose-binding domain Ⅱ at C terminal. Southern blot analysis showed that there were multiple copies of RS-eng-1 within Radopholus similis genome. In situ hybridization showed RS-eng-1 was expressed in Radopholus similis' esophageal gland cells. Genomic analysis demon-strated that Rs-eng-1 contained six introns demarcated by 5'-GT...AG-3' in the slpice sites and phylogenic analysis suggested that RS-eng-1 had a strong homology to β-1, 4-endoglucanase genes from Bacillus subtilis and Erwina carotovora, which may be indicative of an ancient horizontal gene transfer.

Key words: Radopholus similis, banana, β-1, 4-endoglucanase, glycosyl hydrolase family 5, in situ hybridization