Worm Breeder's Gazette 5(2): 15
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
As described at the CSH Conference (May, 1979), the banding patterns of the -mercaptoethanol-soluble proteins (collagens) of the L1, dauer, L4, and adult cuticles are different on SDS gels. Only one major protein (adult component cpH) appears to be conserved between all these stages. Four of the five major proteins present in the L4 cuticle also appear to be present in the L1 cuticle. The exceptional L4 protein is one that is also present in the adult (adult component cpE). The L1 cuticle does contain at least two proteins not present in the L4 cuticle. The dauer and adult cuticles each contain many (3- 4) proteins not present in the other stages. These findings complement the ultrastructural studies which demonstrate considerable similarity in the morphologies of the L1, L2, L3, and L4 cuticles. Certain structural differences do exist between the cuticles of these stages, however; for instance, the L1 cuticle has alae. The dauer and adult cuticles differ markedly from each other and from the cuticles of the other stages. Only the adult cuticle consists of two clearly separate layers. The amino acid compositions of the ME-soluble and insoluble proteins of the dauer, L4, and adult cuticles have been determined. The soluble proteins of the L4 and adult cuticles have a fairly similar composition; these proteins contain large amounts of glycine ( 26%), proline (11-12%), hydroxyproline (10-11%), and cysteine (3%). The soluble proteins of the dauer cuticle are quite distinct, however, containing increased amounts of glycine (29%) and cysteine (6%), and decreased amounts of proline (9%) and hydroxyproline (5%). Hydroxylysine is present in the dauer proteins (.1%), but absent form the L4 and adult proteins. The dauer proteins also contain 2-3 times more hydrophobic residues than the proteins of the other stages. The insoluble proteins of the dauer, L4, and adult cuticles differ in composition from each other and from the corresponding soluble proteins of each stage. The insoluble proteins are also rich in glycine, proline, and hydroxyproline, but, at least for the adult proteins, enzyme digestion studies suggest that they are not collagens. Electron microscopy indicates that nearly all of the L4 and adult cuticle is solubilized by ME. Only the external cortical layer and a small amount of adhering material appears resistant to this treatment. The architecture of the dauer cuticle, however, is only mildly affected by ME, although a substantial amount of material is extracted. The material that underlies the radial striations, the material that forms the interstices of the radial striations, and portions of the alae are solubilized by ME. The dauer cuticle contracts when treated with ME due to contraction of the lattice structure that forms the radial striations.