Profiling gene expression responses of coral larvae (Acropora millepora) to elevated temperature and settlement inducers using a novel RNA-Seq procedure

Abstract

Elevated temperatures resulting from climate change pose a clear threat to reef-building corals; however, the traits that might influence corals' survival and dispersal during climate change remain poorly understood. Global gene expression profiling is a powerful hypothesis-forming tool that can help elucidate these traits. Here, we applied a novel RNA-Seq protocol to study molecular responses to heat and settlement inducers in aposymbiotic larvae of the reef-building coral Acropora millepora. This analysis of a single full-sibling family revealed contrasting responses between short- (4-h) and long-term (5-day) exposures to elevated temperatures. Heat shock proteins were up-regulated only in the short-term treatment, while the long-term treatment induced the down-regulation of ribosomal proteins and up-regulation of genes associated with ion transport and metabolism (Ca(2+) and CO(3)(2-)). We also profiled responses to settlement cues using a natural cue (crustose coralline algae, CCA) and a synthetic neuropeptide (GLW-amide). Both cues resulted in metamorphosis, accompanied by differential expression of genes with known developmental roles. Some genes were regulated only by the natural cue, which may correspond to the recruitment-associated behaviour and morphology changes that precede metamorphosis under CCA treatment, but are bypassed under GLW-amide treatment. Validation of these expression profiles using qPCR confirmed the quantitative accuracy of our RNA-Seq approach. Importantly, qPCR analysis of different larval families revealed extensive variation in these responses depending on genetic background, including qualitative differences (i.e. up-regulation in one family and down-regulation in another). Future studies of gene expression in corals will have to address this genetic variation, which could have important adaptive consequences for corals during global climate change.

Contrasting transcriptome response to thermal stress in two key zooplankton species, Calanus finmarchicus and C. glacialis

“…pdf) demonstrates the reliability of our RNA-seq results, particularly in C. finmarchicus, where the correlation is similar to other studies on non-model species (e.g. Meyer et al 2011). The reduced strength of correlation between qPCR and RNA-seq in C. glacialis is likely due to the limited sequencing depth and small FC in gene expression under stress conditions.…”

“…Meistertzheim et al 2007), while C. glacialis did not reveal to keep homeostasis. Similarly to C. finmarchicus, a higher number and little overlap between differentially expressed genes after LTS compared to STS is observed in the coral Acropora millepora under exposure to elevated temperatures (Meyer et al 2011). Consequently, functional divergence in response to STS and LTS may exist, and highlights the importance of stress duration for experiments that aim to investigate resiliencepotential of species under climate change.…”

Marine Invertebrate Larvae Associated with Symbiodinium: A Mutualism from the Start?

“…At this time, the expression of heat-shock proteins and oxidative-stress genes becomes detectable (DeSalvo et al, 2008(DeSalvo et al, , 2010RodriguezLanetty et al, 2009;Meyer et al, 2011). Data by Mies et al (2017c) show that coral and giant clam larvae from Vietnam bleach at 29 • C and hardly survive past 32 • C. However, the highlytolerant larvae of Pocillopora damicornis (from Okinawa, Japan) have been shown to withstand a temperature of 32 • C, despite losing the majority of its symbiont cells (Haryanti et al, 2015).…”

Evaluating the causal basis of ecological success within the scleractinia: an integral projection model approach

“…While it has rapidly become clear that the responses of corals to OA and thermal stress, individually or interactively, are not uniform among species (Loya et al 2001;Pandolfi et al 2011;Comeau et al 2013), progress in understanding the causal basis of this variability has been slow. There are exceptions to this generality, notably with molecular genetic tools, for example, being used to clarify cellular function (Meyer et al 2011;Miller et al 2011), host taxonomy (Forsman et al 2009;Stat et al 2012), and the roles of Symbiodinium genotypes in affecting holobiont biology (Hennige et al 2009;Putnam et al 2012;Yuyama et al 2012). There is a clear need for more information in order to understand the factors promoting coral success in the face of environmental challenges.…”