Characterisation and developmental expression of a chitinase gene in Heterodera glycines.

A chitinase full-length cDNA (designated Hg-chi-1) was isolated from a Heterodera glycines oesophageal gland cell-specific long-distance PCR cDNA library. The cDNA hybridised to genomic DNA of H. glycines in Southern blots. The Hg-chi-1 cDNA contained an open reading frame encoding 350 amino acids with the first 23 amino acids being a putative signal peptide for secretion. Hg-CHI-1 contained a chitinase 18 family catalytic domain, and chitinolytic activity of recombinant Hg-CHI-1 was confirmed in glycol-chitin substrate gel electrophoresis. In situ mRNA hybridisation analyses showed that transcripts of Hg-chi-1 accumulated specifically in the subventral oesophageal gland cells of parasitic stages of H. glycines, but Hg-chi-1 expression was not detected in eggs or hatched pre-parasitic second-stage juveniles, suggesting that this chitinase does not have a role in egg hatching of H. glycines. The biological function of Hg-CHI-1 in H. glycines remains to be determined.