Chemical Fate of a Metamorphic Inducer in Larvae-like Buds of the Cnidarian Cassiopea andromeda

Abstract

Larvae-like vegetative buds of the scyphozoan Cassiopea andromeda metamorphose into polyps in the presence of oligopeptides that have a well-defined primary structure. Buds were incubated with the hexapeptide 14C-dansyl-GPGGPA, a representative inducer. Autoradiography of longitudinal sections of these buds revealed rapid internalization of peptide by the buds. Silver grain density was highest in the pre-pedal disc region (or aboral knob) of metamorphosing buds. Larvae and buds sporadically explore their habitat with this aboral knob, searching for a suitable solid substrate to which irreversible attachment will be made. Buds were incubated for 3, 8, or 16 h with 14C-dansyl-GPGGPA, then homogenized and the supernatants analyzed to determine the chemical fate of the inducer. The signal molecule was shown to be partly degraded to 14C-dansyl-GP, partly to 14C-dansyl-G, and in part still present in its original structure. These cleavage products were also found in the surrounding medium after an incubation time of 8 h with 14C-dansyl-GPGGPA, but did not induce metamorphosis. This study suggests that exposure of metamorphosis-inducing peptides to buds of Cassiopea andromeda results in signal termination.

Upside-Down but Headed in the Right Direction: Review of the Highly Versatile Cassiopea xamachana System

“…Collagen digestion by Vibrio alginolyticus also led to the production of inductive fractions, suggesting the involvement of a peptidic cue in polyp development (Hofmann and Brand, 1987). The discovery that certain small molecules and peptides are involved in polyp metamorphosis has led to the design of a synthetic peptide (GPGGPA) with settlement and metamorphosis inductive capacities (Fleck, 1998). Research efforts attempting to isolate a peptidic cue from Cassiopea's natural substrate, degraded mangrove leaves, resulted in extraction of several bioactive fractions, one of which contained a proline-rich 5.8 kDa peptide capable of inducing settlement and metamorphosis, although the precise amino acid sequence of this peptide or other natural cues have yet to be determined .…”

Role of Protein Kinase C, G-Protein Coupled Receptors, and Calcium Flux During Metamorphosis of the Sea UrchinStrongylocentrotus purpuratus

“…In some species, activation of the morphogenetic changes can be triggered, in the absence of natural cues, by several organic and inorganic compounds, which have been used as artificial inducers. These include neuroactive substances such as ␥-aminobutyric acid (GABA), 3,4-dihydroxyphenylalanine (DOPA), catecholamines, and choline derivatives, organic and inorganic compounds, and the inorganic ions Mg 2ϩ , Li ϩ , NH 4 ϩ , Cs ϩ , and K ϩ (Pearce and Scheibling, 1994;Avila et al, 1996;Fleck, 1998;Kawaii et al, 1999;Carpizo-Ituarte et al, 2002).…”

A proline-rich peptide originating from decomposing mangrove leaves is one natural metamorphic cue of the tropical jellyfish Cassiopea xamachana

“…(Fitt & Hofmann 1985, Fitt et al 1987, Hofmann & Brand 1987, Fleck & Hofmann 1990, Bischoff et al 1991, Fleck & Bischoff 1993, Fleck 1997, Fleck 1998, Walther & Fleck 1998. Like the characterized natural cue originating from mangrove leaves, the most effective synthetic peptidic inducers were mainly composed of proline and glycine residues (Fitt & Hofmann 1985, Hofmann & Brand 1987, Fleck & Hofmann 1990, Fleck & Bischoff 1993, Walther & Fleck 1998.…”