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

Abstract

A proline-rich peptide originating from decomposing mangrove leaves is one natural metamorphic cue of the tropical jellyfish Cassiopea xamachana 'Lehrstuhl fiir Spezielle Zoologie, Ruhr-Universitit. D-44780 Bochum. Germany 'Institute of Ecology, University of Georgia, Athens. Georgia 30602-2602. USA 3Complex Carbohydrate Research Center, University of Georgia, Athens. Georgia 30602-4712, USA ABSTRACT: Planula larvae of the scyphozoan Cassiopea xamachana settle and n~etamorphose on degrading mangrove leaves of Rhizophora mangle that lie submerged In shallow water mangrove ecosystems. Our prior study (Fleck & Fitt 1999; J Exp Mar Biol Ecol 234:83-94) indicated that marine bacteria are involved in the release of at least 1 peptidic compound from such leaves. The goal of our present study was to isolate and purify at least 1 natural peptidic cue originating from deteriorating leaves by means of ultrafiltration, gel filtration and reversed phase HPLC and subsequently obtain characteristic data of this cue. The ultrafiltrate (110 kD) of the homogenate of decaying mangrove leaves was subjected to gel filtration on a Sephadex G 25 column, resulting in 3 fractions which were tested for their capacity to induce metamorphosis of planula larvae in bioassays performed in the laboratory. Fraction I ( 2 5 kD) was most effective in inducing metamorphosis of 75 % of planulae at 1 mg freeze-dried material ml-' seawater within 24 h. Fractions I1 and I11 (both 25 kD) resulted In metamorphosis of only 1 % of larvae or less within 72 h when applied at 5 mg rnl-' Isochratic HPLC separation of Fraction I with 24 % methanol yielded 2 biologically active fractions. One fraction (A/B), which induced 41 % of the larvae to metamorphose at 0.9 mg lyophilized material ml-' seawater within 24 h, consisted of a mixture of at least 2 subfractions and was not further analyzed. The other fraction (C) effected metamorphosis of 85 % of larvae at a concentration of 0.5 mg rnl-' within 24 h. Matrix-assisted laser desorption ionization (MALDI) mass spectrometry of this fraction revealed a molecular weight of approximately 5.8 kD. Automated amino acid analysis showed that Fraction C was rich in proline (ca 44%) and glycine residues (ca 16%), corresponding to characteristic proline-rich cell wall proteins of plants. Automated sequencing of the natural inducer failed due to a blocked amino terminus. The results of our present study suggest that metamorphic inducers for C. xamachana may emerge nonspecifically as a byproduct of bacterial degradation of deteriorating, proteinaceous plant tissue in their habitat.

Comparative genomic insights into bacterial induction of larval settlement and metamorphosis in the upside-down jellyfish Cassiopea

“…As with previous studies (7, 21), C. xamachana settled and metamorphosed in response to natural substrates. We found larvae responded to both organic and inorganic substrates, including sand and bivalve shell fragments collected from onshore and offshore sites (Fig.…”

“…Cholera toxin isolated from V. cholerae was also found to induce settlement and metamorphosis (19), and an extract from collagen digested by V. alginolyticus was also found to be inductive (20). In their natural environment, brooded C. xamachana larvae are released into the water column and will often settle preferentially onto the underside of degrading mangrove leaves (7, 21). When treated with antibiotics, larval settlement and metamorphosis is abolished in response to mangrove leaves.…”

Biofouling and antifouling

“…35,37 In contrast, larval settlement of the tropical species C. xamachana is induced by a 5.8 kDa peptide rich in proline and glycine produced by bacterial decomposition of mangrove leaves of Rhizophora mangle, though it was effective only at a high concentration (86 µM). 39, 40 Larvae of the stony coral Agaricia humilis settle and metamorphose in response to a highly sulfated lipoglycosaminoglycan containing repeating β (1,4)-linked N-acetyllactosamine sulfate units with aliphatic side chains present on the surface of crustose coralline red algae such as Hydrolithon boergesenii. 41-43 A bacterial species of Pseudoalteromas isolated from the crustose coralline red alga H. onkodes induced larval metamorphosis in the coral Acropora willisae, 44 but no chemical characterization of the cue was made.…”

Comparative Genomic Insights into Bacterial Induction of Larval Settlement and Metamorphosis in the Upside-Down Jellyfish Cassiopea

“…Cholera toxin isolated from V. cholerae was also found to induce settlement and metamorphosis ( 19 ), and an extract from collagen digested by V. alginolyticus was also found to be inductive ( 20 ). In their natural environment, brooded C. xamachana larvae are released into the water column and will often settle preferentially onto the underside of degrading mangrove leaves ( 7 , 21 ). When treated with antibiotics, larval settlement and metamorphosis is abolished in response to mangrove leaves.…”

“…These findings suggest bacteria associated with degrading leaves may be a source of the inductive cue of Cassiopea . In a follow-up study, Fleck and Fitt ( 21 ) showed a water soluble, 5.8 kDa proline-rich peptide extracted from degraded mangrove leaves to be an inducer of settlement in C. xamachana . However, the originating bacterial source of the cue, and whether the cue is a by-product of leaf degradation, remains unknown.…”