Proteomic analysis of bleached and unbleached Acropora palmata , a threatened coral species of the Caribbean

Abstract

There has been an increase in the scale and frequency of coral bleaching around the world due mainly to changes in sea temperature. This may occur at large scales, often resulting in significant decline in coral coverage. In order to understand the molecular and cellular basis of the ever-increasing incidence of coral bleaching, we have undertaken a comparative proteomic approach with the endangered Caribbean coral Acropora palmata. Using a proteomic tandem mass spectrometry approach, we identified 285 and 321 expressed protein signatures in bleached and unbleached A. palmata colonies, respectively, in southwestern Puerto Rico. Overall the expression level of 38 key proteins was significantly different between bleached and unbleached corals. A wide range of proteins was detected and categorized, including transcription factors involved mainly in heat stress/UV responses, immunity, apoptosis, biomineralization, the cytoskeleton, and endo-exophagocytosis. The results suggest that for bleached A. palmata, there was an induced differential protein expression response compared with those colonies that did not bleach under the same environmental conditions.

Coral Reef Bleaching: An Ecological and Biological Overview

“…Recent investigations have examined the bleaching phenomenon employing genomic and transcriptomic approaches in order to measure changes in the expression of genes and transcripts during thermal stress and bleaching in different cnidarian species [100], including Acropora nana [21], Stylophora pistillata [22], Acropora millepora [101], Acropora palmate [24], Aiptasia pallida [25], Orbicella faveolata [23], and Acropora hyacinthus [27]. The results from those studies revealed that differential expression patterns occur between normal and bleached specimens, providing evidence that several important cell processes are affected by bleaching, such as stress response, Ca 2+ homeostasis, cytoskeleton organization, cell transport, cell proliferation, apoptosis, calcification, protein expression, immune response, and metabolism, among others [21, 23-25, 27, 29, 101].…”

“…On the other hand, proteomic approaches have been applied to assess the effect of post-translational environmental stress on marine organisms [29. A recent study carried out on Acropora palmata showed that bleaching induced a differential protein expression response in this cnidarian. Thirty-eight key proteins were differentially expressed, primarily transcription factors involved in heat stress/UV responses, immunity, apoptosis, biomineralization, the cytoskeletal organization, and endo-exophagocytosis [24].…”

“…The US National Oceanic and Atmospheric Administration (NOAA) coral reef watch, the Global Coral Reef Monitoring Network (GCRMN), as well as other environmental agencies around the world have been monitoring mass coral bleaching events for more than a decade, in order to understand conditions that cause bleaching and to develop measures to rehabilitate reefs [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. On the other hand, academic researchers have addressed the study of this phenomenon employing different approaches, including genomics, transcriptomics, and proteomics to better comprehend the molecular mechanisms that provoke it, its consequences, and the potential adaptive response of cnidarians to this condition [21][22][23][24][25][26][27][28][29]. Undoubtedly, bleaching represents an enormous threat to the survival of coral reefs, as bleached organisms display an increased susceptibility to pathogens, a decreased resistance to predators and bioeroders, declines in reef calcification, depressed growth and reproduction rates, and a lessening of ability to repair damages [15][16][17][18].…”

Comparative evaluation of five protocols for protein extraction from stony corals (Scleractinia) for proteomics

“…Comparative proteomics can provide an overall view of biological mechanisms of coral bleaching, diseases and responses to the environment changes. In recent years, proteomic analysis has been used to study corals and their symbionts . However, it is not easy to extract proteins in high quality from stony coral, which is competent for coral proteomic research.…”

“…However, it is not easy to extract proteins in high quality from stony coral, which is competent for coral proteomic research. The current protein extraction protocols from stony corals reported in the literature include metaproteomic extraction protocol using TRIzol , glass bead‐assisted extraction (GBAE) from skeleton‐free coral tissue , sonication‐assisted extraction (SAE) with rehydration buffer , radioimmunoprecipitation (RIPA) buffer‐assisted extraction after isolation of coral tissue layers by N‐acetylcysteine treatment , and skeleton protein extraction using trichloroacetic acid (TCA)‐acetone or chloroform‐methanol precipitation , or direct ultrafiltration with 10 kDa cutoff membrane after skeleton decalcified by acid. Those protocols are practicable for different experimental purposes, but a comparative evaluation of them was still not available.…”