Differential Gene Expression at Coral Settlement and Metamorphosis - A Subtractive Hybridization Study

Abstract

BackgroundA successful metamorphosis from a planktonic larva to a settled polyp, which under favorable conditions will establish a future colony, is critical for the survival of corals. However, in contrast to the situation in other animals, e.g., frogs and insects, little is known about the molecular basis of coral metamorphosis. We have begun to redress this situation with previous microarray studies, but there is still a great deal to learn. In the present paper we have utilized a different technology, subtractive hybridization, to characterize genes differentially expressed across this developmental transition and to compare the success of this method to microarray.Methodology/Principal FindingsSuppressive subtractive hybridization (SSH) was used to identify two pools of transcripts from the coral, Acropora millepora. One is enriched for transcripts expressed at higher levels at the pre-settlement stage, and the other for transcripts expressed at higher levels at the post-settlement stage. Virtual northern blots were used to demonstrate the efficacy of the subtractive hybridization technique. Both pools contain transcripts coding for proteins in various functional classes but transcriptional regulatory proteins were represented more frequently in the post-settlement pool. Approximately 18% of the transcripts showed no significant similarity to any other sequence on the public databases. Transcripts of particular interest were further characterized by in situ hybridization, which showed that many are regulated spatially as well as temporally. Notably, many transcripts exhibit axially restricted expression patterns that correlate with the pool from which they were isolated. Several transcripts are expressed in patterns consistent with a role in calcification.ConclusionsWe have characterized over 200 transcripts that are differentially expressed between the planula larva and post-settlement polyp of the coral, Acropora millepora. Sequence, putative function, and in some cases temporal and spatial expression are reported.

Proteomic analysis of skeletal organic matrix from the stony coral Stylophora pistillata

“…We compared these four predicted proteins from S. pistillata with pre-and postsettlement genes in Acropora millepora larvae as described by Hayward et al (31). A. millepora genes A9, A90, and A102 are ≥40% similar to the P5 protein found in this study, with blastp e-values ranging from 10 −15 to 10 −23 .…”

“…To date, only one coral SOM protein, galaxin, has been fully sequenced and its role in the biomineralization process is not well understood because it does not bind calcium (27). Other proteins hypothesized to play a role in the mineralizing space between the calicoblastic cells and the skeleton include carbonic anhydrases (28), collagen (12), ion transporters (29), cysteine-rich proteins (30), von Willebrand factor type A domain-containing proteins and zona pellucidas (31), and secreted acidic proteins (18,32). Together, these proteins may represent a "biomineralization toolkit" of calcifying proteins in corals.…”

Two apextrin-like proteins mediate extracellular and intracellular bacterial recognition in amphioxus

“…Apextrin and its homologs have been repeatedly documented since 1998, but their structures and functions have remained elusive (30,31,(35)(36)(37)(38)(39)(40)(41)(42). Here, we demonstrate that ALPs contain ApeC, a novel protein domain structure that is conserved in several invertebrate lineages and capable of recognizing the bacterial cell wall component PGN and its moiety MDP.…”

Colony formation in <i>Phaeocystis antarctica</i>: connecting molecular mechanisms with iron biogeochemistry

“…5 and S1). In biomineralizing organisms, such as corals, glycoproteins with von Willebrand domains are hypothesized to play a role in the formation of the extracellular organic matrix through adhesion (Drake et al, 2013;Hayward et al, 2011) by laying the scaffolding for calcification. Orthologs of the von Willebrand proteins that contain these domains have also been characterized in humans and have protein-binding capabilities, which are important for coagulation (Ewenstein, 1997).…”