Identification and molecular characterization of a new β-1,4-endoglucanase gene (Ha-eng-1a) in the cereal cyst nematode Heterodera avenae

Secretory proteins encoded by genes expressed in the pharyngeal gland cells of plantparasitic nematodes have key roles in nematode parasitism of plants. A new ß-1,4-endoglucanase gene (designated Ha-eng-1a) was isolated from the cereal
cyst nematode Heterodera avenae. The cDNA of Haeng-1a encoded a deduced 463-amino acid sequence containing a catalytic domain and a cellulose binding module separated by a linker. The genomic DNA of Ha-eng-1a is 2,129-bp long, containing eight introns ranging from 56 bp to157 bp and nine exons ranging from 70 bp to 299 bp. Southern blot analysis revealed that the Ha-eng-1a gene has two copies. In situ hybridization showed that the Ha-eng-1a transcripts specifically accumulated in the two subventral gland cells of the second-stage juveniles. There was evidence for cellulase activity of the recombinant protein Ha-eng-1a in vitro. The results indicated that this ß-1,4-endoglucanase gene may play a crucial role in plant cell wall-degradation during penetration and migration of nematodes in the host roots.