Molecular characterisation and developmental expression of a cellulose-binding protein gene in the soybean cyst nematode Heterodera glycines

Abstract

Secretory proteins encoded by ‘parasitism genes’ expressed in the oesophageal gland cells of plant-parasitic nematodes play key roles in nematode infection and parasitism of host plants. A cellulose-binding protein-encoding cDNA, designated Hg-cbp-1, was cloned from a Heterodera glycines oesophageal gland-cell long-distance PCR cDNA library. The cDNA hybridised to genomic DNA of H. glycines in Southern blots, and the genomic sequence of Hg-cbp-1 contained only one intron. The Hg-cbp-1 cDNA contained an open reading frame encoding 132 amino acids, with a predicted signal peptide sequence for secretion and a cellulose-binding domain. Bacterial expressed recombinant HG-CBP-1, minus the signal peptide sequence, had no hydrolytic activity on carboxymethyl-cellulose but was able to bind to cellulose. The developmental expression of Hg-cbp-1, determined by real-time reverse transcriptase PCR, showed that Hg-cbp-1 is expressed throughout the parasitic cycle of H. glycines, with a relatively higher expression level in developing parasitic stages.