Dataset Information

The Complexity of the Holobiont in the Red Sea Coral Euphyllia paradivisa under Heat Stress.

ABSTRACT: The recognition of the microbiota complexity and their role in the evolution of their host is leading to the popularization of the holobiont concept. However, the coral holobiont (host and its microbiota) is still enigmatic and unclear. Here, we explore the complex relations between different holobiont members of a mesophotic coral Euphyllia paradivisa. We subjected two lines of the coral-with photosymbionts, and without photosymbionts (apo-symbiotic)-to increasing temperatures and to antibiotics. The different symbiotic states were characterized using transcriptomics, microbiology and physiology techniques. The bacterial community's composition is dominated by bacteroidetes, alphaproteobacteria, and gammaproteobacteria, but is dependent upon the symbiont state, colony, temperature treatment, and antibiotic exposure. Overall, the most important parameter determining the response was whether the coral was a symbiont/apo-symbiotic, while the colony and bacterial composition were secondary factors. Enrichment Gene Ontology analysis of coral host's differentially expressed genes demonstrated the cellular differences between symbiotic and apo-symbiotic samples. Our results demonstrate the significance of each component of the holobiont consortium and imply a coherent link between them, which dramatically impacts the molecular and cellular processes of the coral host, which possibly affect its fitness, particularly under environmental stress.

SUBMITTER: Meron D

PROVIDER: S-EPMC7143197 | biostudies-literature | 2020 Mar

REPOSITORIES: biostudies-literature

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Publications

The Complexity of the Holobiont in the Red Sea Coral <i>Euphyllia paradivisa</i> under Heat Stress.

Meron Dalit D Maor-Landaw Keren K Eyal Gal G Elifantz Hila H Banin Ehud E Loya Yossi Y Levy Oren O

Microorganisms 20200306 3

The recognition of the microbiota complexity and their role in the evolution of their host is leading to the popularization of the holobiont concept. However, the coral holobiont (host and its microbiota) is still enigmatic and unclear. Here, we explore the complex relations between different holobiont members of a mesophotic coral <i>Euphyllia paradivisa</i>. We subjected two lines of the coral-with photosymbionts, and without photosymbionts (apo-symbiotic)-to increasing temperatures and to ant ...[more]

PMID: 32155796

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Project description:Over the past several decades, corals worldwide have been affected by global warming, experiencing severe bleaching events that have often lead to coral death. The symbiotic Red Sea coral Stylophora pistillata is considered an opportunistic ‘r’ strategist, thriving in relatively unstable and unpredictable environments, and it is considered a stress-tolerant species. This study aimed to examine S. pistillata gene expression and to clarify the cellular pathways that are active during short-term heat stress caused by an increase from 24°C to 34°C over a 10-day period. Total RNA was extracted from heat-stressed coral fragments, labeled and hybridized against a designated S. pistillata custom microarray containing approximately 12,000 genes. Our results show that the heat stress reaction was sighted from 32°C and intensified significantly after 34°C treatment. Protein interaction networks of up- and down-regulated genes were constructed. The main clustering groups of up-regulated genes were ER stress and ER protein folding, cell cycle, ubiquitin-mediated proteolysis, cell death and cell death regulation and cellular stress response genes. These genes were enriched in cellular pathways related to the unfolded protein response (UPR) in the ER, ER-associated degradation (ERAD) and ubiquitin-mediated proteolysis. An analysis of the down-regulated genes yielded different clusters of genes related to extracellular matrix and actin organization, collagen, negative regulation of cell death and the Notch and Wnt signaling pathways. Genes encoding redox regulation proteins and molecular chaperones may be considered accurate “early warning genes”, while genes related to sensing and repairing DNA damage are severe heat-related genes. Here, we suggest that during short-term heat stress, S. pistillata might divert cellular energy into mechanisms such as UPR and ERAD at the expense of growth and biomineralization processes in an effort to recover from the stress.

Project description:The ability of corals to withstand changes in their surroundings is a critical survival mechanism for coping with environmental stress. While many studies have examined responses of the coral holobiont to stressful conditions, its capacity to reverse responses and recover when the stressor is removed is not well-understood. In this study, we investigated among-colony responses of Pocillopora acuta from two sites with differing distance to the mainland (Kusu (closer to the mainland) and Raffles Lighthouse (further from the mainland)) to heat stress through differential expression analysis of target genes and quantification of photophysiological metrics. We then examined how these attributes were regulated after the stressor was removed to assess the recovery potential of P. acuta. The fragments that were subjected to heat stress (2 °C above ambient levels) generally exhibited significant reduction in their endosymbiont densities, but the extent of recovery following stress removal varied depending on natal site and colony. There were minimal changes in chl a concentration and maximum quantum yield (Fv/Fm, the proportion of variable fluorescence (Fv) to maximum fluorescence (Fm)) in heat-stressed corals, suggesting that the algal endosymbionts' Photosystem II was not severely compromised. Significant changes in gene expression levels of selected genes of interest (GOI) were observed following heat exposure and stress removal among sites and colonies, including Actin, calcium/calmodulin-dependent protein kinase type IV (Camk4), kinesin-like protein (KIF9), and small heat shock protein 16.1 (Hsp16.1). The most responsive GOIs were Actin, a major component of the cytoskeleton, and the adaptive immune-related Camk4 which both showed significant reduction following heat exposure and subsequent upregulation during the recovery phase. Our findings clearly demonstrate specific responses of P. acuta in both photophysiological attributes and gene expression levels, suggesting differential capacity of P. acuta corals to tolerate heat stress depending on the colony, so that certain colonies may be more resilient than others.

Dataset Information

The Complexity of the Holobiont in the Red Sea Coral Euphyllia paradivisa under Heat Stress.

Publications

The Complexity of the Holobiont in the Red Sea Coral <i>Euphyllia paradivisa</i> under Heat Stress.

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