The genetics of colony form and function in Caribbean Acropora corals

Abstract

BackgroundColonial reef-building corals have evolved a broad spectrum of colony morphologies based on coordinated asexual reproduction of polyps on a secreted calcium carbonate skeleton. Though cnidarians have been shown to possess and use similar developmental genes to bilaterians during larval development and polyp formation, little is known about genetic regulation of colony morphology in hard corals. We used RNA-seq to evaluate transcriptomic differences between functionally distinct regions of the coral (apical branch tips and branch bases) in two species of Caribbean Acropora, the staghorn coral, A. cervicornis, and the elkhorn coral, A. palmata.ResultsTranscriptome-wide gene profiles differed significantly between different parts of the coral colony as well as between species. Genes showing differential expression between branch tips and bases were involved in developmental signaling pathways, such as Wnt, Notch, and BMP, as well as pH regulation, ion transport, extracellular matrix production and other processes. Differences both within colonies and between species identify a relatively small number of genes that may contribute to the distinct “staghorn” versus “elkhorn” morphologies of these two sister species.ConclusionsThe large number of differentially expressed genes supports a strong division of labor between coral branch tips and branch bases. Genes involved in growth of mature Acropora colonies include the classical signaling pathways associated with development of cnidarian larvae and polyps as well as morphological determination in higher metazoans.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-1133) contains supplementary material, which is available to authorized users.

Differential localization of ion transporters suggests distinct cellular mechanisms for calcification and photosynthesis between two coral species

“…For example, expression of the NKA gene was increased in rapidly calcifying regions of the corals A. cervicornis and A. palmata, while levels of multiple PMCA trancripts remained constant (13). These data suggest that NKA activity helps drive coral calcification and further calls into doubt the presumed role of PMCA in calcification.…”

Diurnal and nocturnal transcriptomic variation in the Caribbean staghorn coral, Acropora cervicornis

“…; Hemond et al . ) using CLC Genomics Workbench (CLC bio, Aarhus, Denmark). Reference transcriptome annotation was conducted using translated nucleotide queries against the curated UniProt/Swiss‐Prot database and a threshold E‐value of 10 −5 .…”

“…Differences in gene expression between branch bases and tips have been found to represent a substantial fraction, approximately 10%, of the transcriptome, including functions such as developmental signalling, metabolism and calcification (Hemond et al . ). In corals with DOL and variation in the density of Symbiodinium within the colony, such as Acropora s, there may also be location‐specific diel changes in gene expression.…”

Physiological integration of coral colonies is correlated with bleaching resistance

“…Communication pathways include skeletal features that allow the gastrovascular cavities of neighboring polyps to be continuous, such as skeletal voids (perforate skeleton, commonly found in genera such as Acropora, Montipora, and Porites; van Woesik et al 2013) that allow tissue to transverse through the skeleton (Yost et al 2013), or inter-polyp alignment of septa (continuity of costosepta, such as the confluent costosepta of Favites abdita or Favites halicora; Huang et al 2014) that demonstrate alignment of mesenteries and may allow tissue connections to continue above the surface of the skeleton (Coates & Oliver 1973, Coates & Jackson 1987. Inferences of reliance and coordination among polyps include polymorphic calices that reflect differential functions of polyps and division of labor among colonial modules (polymorphic polyps, such as the apical polyps of Acropora at the growing tips of branches that are larger, have fewer tentacles, lower Symbiodinium density, and no gonads compared to the axial polyps; Oliver 1984, Hemond et al 2014) and complex colony morphologies that require coordinated skeletal construction to maintain colony dimensions, symmetry, and balance (growth form, such as branching Acropora palmata or Seriatopora caliendrum; Madin et al 2016) (Coates & Oliver 1973, Coates & Jackson 1987. These characters constitute morphological evidence of physiological integration (inferred), rather than direct measurements of interpolypoidal movements of materials or chemical signals (experimentally determined; e.g.…”