Assessing the Impacts of Experimentally Elevated Temperature on the Biological Composition and Molecular Chaperone Gene Expression of a Reef Coral

Abstract

Due to the potential for increasing ocean temperatures to detrimentally impact reef-building corals, there is an urgent need to better understand not only the coral thermal stress response, but also natural variation in their sub-cellular composition. To address this issue, while simultaneously developing a molecular platform for studying one of the most common Taiwanese reef corals, Seriatopora hystrix, 1,092 cDNA clones were sequenced and characterized. Subsequently, RNA, DNA and protein were extracted sequentially from colonies exposed to elevated (30°C) temperature for 48 hours. From the RNA phase, a heat shock protein-70 (hsp70)-like gene, deemed hsp/c, was identified in the coral host, and expression of this gene was measured with real-time quantitative PCR (qPCR) in both the host anthozoan and endosymbiotic dinoflagellates (genus Symbiodinium). While mRNA levels were not affected by temperature in either member, hsp/c expression was temporally variable in both and co-varied within biopsies. From the DNA phase, host and Symbiodinium hsp/c genome copy proportions (GCPs) were calculated to track changes in the biological composition of the holobiont during the experiment. While there was no temperature effect on either host or Symbiodinium GCP, both demonstrated significant temporal variation. Finally, total soluble protein was responsive to neither temperature nor exposure time, though the protein/DNA ratio varied significantly over time. Collectively, it appears that time, and not temperature, is a more important driver of the variation in these parameters, highlighting the need to consider natural variation in both gene expression and the molecular make-up of coral holobionts when conducting manipulative studies. This represents the first study to survey multiple macromolecules from both compartments of an endosymbiotic organism with methodologies that reflect their dual-compartmental nature, ideally generating a framework for assessing molecular-level changes within corals and other endosymbioses exposed to changes in their environment.

Response to pH stress in the reef-building coral Pocillopora capitata (Anthozoa: Scleractinia)

“…In this regard, there is some variability in the observations related to stress effectors. Mayfield et al (2011) reported that thermal stress increased Seriatopora hystrix protein metabolism between 12 and 24 h, followed by a significant decrease Los datos se muestran como media ± EE (n= 3) Diferentes símbolos denotan diferencias significativas entre los tratamientos (P < 0,05). C 1 : tratamiento 7,85/7,95 pH; C 2: tratamiento: 7,60/7,70 pH; CC: tratamiento de control 8,00/8,40 pH at 48 h. By contrast, in the coral Acropora millepora, Hauri et al (2010) reported the persistence of extensive metabolism for up to 240 h after physicochemical stress.…”

Factores asociados a la respuesta de Pocillopora spp. (Anthozoa: Scleractinia) durante un proceso de restauración en la costa del Pacífico mexicano

“…Lo anterior ya había sido observado por Mayfield et al (2011) quienes además postularon que el simbionte aporta únicamente el 10% de los trascriptos de ARN en el coral Seriatopora hystrix. En este sentido también se observó que los morfotipos NCc y NJc presentaron las mayores relaciones de proteína/ADN, lo cual no ocurrió con ninguno de los corales restaurados, y podría ser el reflejo de que, posterior a un año de iniciada la restauración, los CO no alcanzaron el estado trascripcional que caracterizó a los especímenes de control.…”

Uncovering Spatio-Temporal and Treatment-Derived Differences in the Molecular Physiology of a Model Coral-Dinoflagellate Mutualism with Multivariate Statistical Approaches

“…The SHSTTE [12,14] and SHVTS [18,20] are described in prior works. Briefly, whole, unfragmented S. hystrix colonies from Houbihu were exposed to either the control (27 °C) or elevated temperature (30 °C) for 48 hr in the former, and RNAs, DNAs, and proteins were extracted from triplicate colonies housed within each of triplicate tanks at each of the two temperature treatments at each of four sampling times (6,12,24, and 48 hr; 18 samples/sampling time).…”

“…For instance, the common, Indo-Pacific reef-builder Seriatopora hystrix showed no mRNA-level molecular chaperone response when exposed for 2 d to 30 °C [12], a temperature hypothesized to ultimately elicit bleaching in this species based on observations made in Japan and elsewhere [13]. In fact, the expression of only 2 genes out of the 14 targeted (6 from Symbiodinium and 8 from the coral host), the cytoskeleton genes β-actin (actb) and α-tubulin (tuba), were determined by real-time PCR (qPCR) to be affected by temperature [14].…”

“…In fact, the expression of only 2 genes out of the 14 targeted (6 from Symbiodinium and 8 from the coral host), the cytoskeleton genes β-actin (actb) and α-tubulin (tuba), were determined by real-time PCR (qPCR) to be affected by temperature [14]. Mayfield et al [12] hypothesized that such a lack of a molecular chaperone response, in particular, in either compartment of this holobiont ("host+ endosymbiont") may have been due to mRNA "front-loading" (sensu [15]) in samples of this "S. hystrix short-term temperature experiment" (SHSTTE). Briefly, corals of Southern Taiwan inhabit environments characterized by episodic upwelling, whereby temperatures may change by up to 9 °C in a matter of several hours [16].…”