Molecular cloning of Xenopus hatching enzyme and its specific expression in hatching gland cells.

UVS.2 has been known as a cloned cDNA expressed selectively in the hatching gland cells of Xenopus laevis. To determine the molecular identity and function of UVS.2-encoded proteins, antibodies were raised against a bacterially-expressed fusion protein comprising glutathione-S-transferase (GST) and UVS.2. Anti-GST-UVS.2 antibodies inhibited the vitelline envelope digesting activity of the medium (hatching medium) in which dejellied prehatching embryos were cultured. On Western blotting, hatching medium contained 60 kDa and 40 kDa molecules reactive with these antibodies. Whole-mount immunostaining showed a specific localization of UVS.2 protein in the hatching gland cells which appeared first at stage 20, increased in number and intensity to stage 31 then decreased gradually thereafter. Immunoelectron microscopy revealed that UVS.2 protein is localized exclusively in the secretory granules in the hatching gland cells. A cDNA library from the dorsoanterior portion of stage 25 embryos was screened with UVS.2, and a 1.8 kb insert thus cloned contained additional 619bp and 204bp at the 5' and 3' ends of UVS.2, respectively. This clone, designated XHE, contained an open reading frame encoding 514 amino acids including both signal and propeptide sequences. The predicted mature enzyme comprising 425 amino acids consists of about 200 amino acid-long metalloprotease sequence of astacin family at the N-terminus, followed by two repeats of CUB domain each 110 amino acid-length. We conclude that UVS.2 represents an approximately 3/4 C-terminal portion of the hatching enzyme.

Distribution of growth-blocking peptide in the insect central nervous tissue.

Parasitization of the armyworm Pseudaletia separata by the endoparasitic wasp Cotesia kariyai inhibits larval growth and delays pupation, conditions necessary for proper maturation of the parasite larvae. Parasitization is correlated with an elevated level of a 25-amino-acid hormone-like peptide, growth-blocking peptide (GBP, ENFSGGCVAGYMRTPDGRCKPTFYQ). Injection of synthetic GBP into nonparasitized larvae dose dependently mimics the effects of parasitization by delaying the larval development. Here we studied the relationship between parasitization and both the production and distribution of GBP in central nervous tissues. We found that parasitization is correlated with an elevated expression of GBP mRNA, and increased concentrations of both proGBP and GBP in the host insect brain and subesophageal ganglion. The increase in proGBP precedes that of the mature GBP by about 12 h. In situ hybridization analysis using sections of parasitized and nonparasitized larval brains showed strong expression of GBP mRNA in perineural cells and/or class I neuroglia in the rind of both larval brains. The expression in parasitized larval brain-subesophageal ganglion is approximately two- to threefold higher than that in nonparasitized larvae. The presence of GBP in insect neural tissue, and its role in inhibiting growth, suggest an involvement in the regulation of neurosecretory cells.