Stony corals generate their calcium carbonate exoskeleton in a highly controlled biomineralization process mediated by a variety of macromolecules including proteins. Fully identifying and classifying these proteins is crucial to understanding their role in exoskeleton formation, yet no optimal method to purify and characterize the full suite of extracted coral skeletal proteins has been established and hence their complete composition remains obscure. Here, we tested four skeletal protein purification protocols using acetone precipitation and ultrafiltration dialysis filters to present a comprehensive scleractinian coral skeletal proteome. We identified a total of 60 proteins in the coral skeleton, 44 of which were not present in previously published stony coral skeletal proteomes. Extracted protein purification protocols carried out in this study revealed that no one method captures all proteins and each protocol revealed a unique set of method-exclusive proteins. To better understand the general mechanism of skeletal protein transportation, we further examined the proteins' gene ontology, transmembrane domains, and signal peptides. We found that transmembrane domain proteins and signal peptide secretion pathways, by themselves, could not explain the transportation of proteins to the skeleton. We therefore propose that some proteins are transported to the skeleton via non-traditional secretion pathways.
14Stony corals generate their calcium carbonate exoskeleton in a highly controlled 15 biomineralization process mediated by a variety of macromolecules including 16 proteins. Fully identifying and classifying these proteins is crucial to understanding 17 their role in exoskeleton formation, yet no optimal method to extract and isolate and 18 characterize coral skeletal proteins has been established and their complete 19 composition remains obscure. Here, we tested four skeletal protein extraction 20 protocols using acetone precipitation and ultrafiltration dialysis filters to present a 21 comprehensive scleractinian coral skeletal proteome. We identified a total of 60 22 proteins in the coral skeleton, 44 of which were not present in previously published 23 stony coral skeletal proteomes. Extracted protein treatment protocols carried out in 24 this study revealed that there is no "one optimal method" and each protocol revealed a 25 unique set of method-exclusive proteins. To better understand the general mechanism 26 of skeletal protein transportation, we further examined the proteins' gene ontology, 27 transmembrane domains, and signal peptides. We found that transmembrane domain 28 proteins and signal peptide secretion pathways, by themselves, could not explain the 29 transportation of proteins to the skeleton . We therefore propose that proteins are 30 transported to the skeletal via vesicles and possibly non-traditional secretion 31 pathways. 32 2
Black corals (Antipatharia) are among the most common and diverse taxa in mesophotic and aphotic rocky habitats. Studies of their ecology and biology are limited mostly because of the technical challenges involved in deep-water work. Here, we describe taxonomic traits, habitat, and nutrition of 2 species from the upper mesophotic zone of the northern Red Sea, Gulf of Aqaba, Israel. Our study describes a broader distribution of the branched Antipathes griggi, which to date has been primarily found in the Hawaiian Archipelago. Additionally, a new record is reported regarding the coiled Stichopathes spp. discovered at the upper mesophotic zone. The branched A. griggi were more abundant than the coiled Stichopathes spp. in all explored sites, and differences in light and water flow conditions significantly affected their distribution. Both species lacked symbiotic algae (Symbiodiniaceae). Analysis of the amino acid compound-specific stable isotope signature (AA-CSIA) revealed that both antipatharian species show a high trophic position relative to known mixotrophic and heterotrophic corals. Although both species inhabit the same area and are planktivorous, their carbon signature suggests they have different carbon sources. Our findings imply that antipatharians have a vital role in the trophic dynamics of mesophotic coral ecosystems, a unique habitat whose ecology remains largely unexplored.
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