Developmental expression of secretory beta-1,4-endoglucanases in the subventral esophageal glands of Heterodera glycines

Two beta-1,4-endoglucanases (EGases), Hg-eng-1 and Hg-eng-2, were recently cloned from the soybean cyst nematode, Heterodera glycines, and their expre ssion was shown in the subventral esophageal glands of hatched second-stage juveniles (J2). We examined the expression of these EGases in the subventr al glands of all post-embryonic life stages of H. glycines by in situ hybri dization and immunolocalization. The first detectable accumulation of EGase mRNAs occurred in the subventral glands of unhatched J2. EGase transcripts remained detectable in J2 after hatching and during subsequent root invasi on. However, in late parasitic J2 and third-stage juveniles (J3), the perce ntage of individuals that showed EGase transcripts decreased. In female fou rth-stage juveniles and adult females, EGase transcripts were no longer det ected in the subventral glands. EGase hybridization signal reappeared in un hatched males coiled within the J3 cuticle, and transcripts were also prese nt in the subventral glands of migratory adult males. Immunofluorescence la beling showed that EGase translation products are most abundantly present i n the subventral glands of preparasitic J2, migratory parasitic J2, and adu lt males. The presence of EGases predominantly in the migratory stages sugg ests that the enzymes are used by the nematodes to soften the walls of root cells during penetration and intracellular migration.