Isolation of beta-1,4-endoglucanase genes from Globodera tabacum and theirexpression during parasitism

Two beta-1,4-endoglucanase (EGase) cDNAs were isolated from Globodera tabac um, the tobacco cyst nematode, and have been designated as GT-eng-1 and GT- eng-2. GT-eng-1 and GT-eng-2 encode precursor proteins with a predicted sec retion signal sequence, cellulolytic catalytic domain, and a linker domain. The protein product GT-ENG-1 contains an additional 95 amino acid carboxy terminal sequence with strong similarity to type II cellulose binding domai ns. Riboprobes and polyclonal antibodies raised to recombinant cyst nematod e EGases were used to follow expression patterns of EGase transcripts and p roteins throughout the nematode life cycle. EGase transcripts and proteins were specifically detected within the subventral esophageal gland cells of G. tabacum second-stage juveniles (J2) within eggs prior to hatching, in pr eparasitic J2, and in parasitic J2 that had invaded tobacco roots. EGase tr anscripts and proteins were not detected in G. tabacum after the molt to th e sedentary J3, J4, and adult female life stages. Interestingly, EGase tran scription and translation resumed in the subventral esophageal glands of la te J4 males. It is hypothesized that secreted EGases play a major role to f acilitate intracellular migration of G. tabacum within tobacco roots.