Impact of El Niño-Southern Oscillation 2015-2016 on the soluble proteomic profile and cytolytic activity of Millepora alcicornis (“fire coral”) from the Mexican Caribbean

Abstract

Reef-forming cnidarians are extremely susceptible to the “bleaching” phenomenon caused by global warming. The effect of elevated seawater temperature has been extensively studied on Anthozoans; however, to date the impact of thermal stress on the expression of genes and proteins in Hydrozoan species has not been investigated. The present study aimed to determine the differential proteomic profile of Millepora alcicornis, which inhabits the Mexican Caribbean, in response to the El Niño-Southern Oscillation 2015–2016. Additionally, the cytolytic activity of the soluble proteomes obtained from normal and bleached M. alcicornis was assessed. Bleached specimens showed decreased symbiont’s density and chlorophyll a and c2 levels. After bleaching, we observed a differential expression of 17 key proteins, tentatively identified as related to exocytosis, calcium homeostasis, cytoskeletal organization, and potential toxins, including a metalloprotease, a phospholipase A2 (PLA2), and an actitoxin. Although, some of the differentially expressed proteins included potential toxins, the hemolytic, PLA2, and proteolytic activities elicited by the soluble proteomes from bleached and normal specimens were not significantly different. The present study provides heretofore-unknown evidence that thermal stress produces a differential expression of proteins involved in essential cellular processes of Hydrozoan species. Even though our results showed an over-expression of some potential toxin-related proteins, the cytolytic effect (as assessed by hemolytic, PLA2, and caseinolytic activities) was not increased in bleached M. alcicornis, which suggests that the cytolysis is mainly produced by toxins whose expression was not affected by temperature stress. These findings allow hypothesizing that this hydrocoral is able to prey heterotrophically when suffering from moderate bleaching, giving it a better chance to withstand the effects of high temperature.

Ecology, Biology and Genetics ofMilleporaHydrocorals on Coral Reefs

“…have been reported to be among the first cnidarians to lose their zooxanthellae symbionts during widespread bleaching events [134] and they have suffered local or regional extinctions from bleaching in the Pacific [78,85,135]. Numerous investigations of bleaching events on Caribbean and Florida Keys reefs have reported bleaching of Millepora colonies [133,[136][137][138][139], with M. alcicornis, a finely branched species, being the most severely affected reef corals. Such coral morphology has been described to be more susceptible to bleaching than encrusting and massive species [140].…”

“…Nevertheless, many studies have addressed the aetiology and effects of bleaching in Anthozoan species, wherein changes in the expression of genes and proteins were observed, and particularly heat shock proteins and transcription factors [154][155][156][157][158][159]. A recent study demonstrated that bleached specimens of M. alcicornis in Mexican Caribbean undergo a moderate decrease in symbiont's density and photosynthetic pigments, in addition to differential expression of 17 key proteins, such as calmodulin, actin and collagen often coupled with calcium homeostasis, exocytosis and cytoskeleton organization in Anthozoan species [139].…”

Comparative Analysis of the Soluble Proteome and the Cytolytic Activity of Unbleached and Bleached Millepora complanata (“Fire Coral”) from the Mexican Caribbean

“…We found that the levels of 17 key proteins, tentatively identified as related to exocytosis, calcium homeostasis, cytoskeletal organization were modified in bleached M. alcicornis . Moreover, the protein levels of potential toxins, including a metalloprotease, a phospholipase A2 (PLA2), and an actitoxin were also altered [48]. It is obviously very important to continue studying the consequences of high water temperature on hydrocorals.…”

Marine Natural Products from the Yucatan Peninsula

“…Out of the 66 marine natural products identified, 26 correspond to structures that were not previously reported. These 26 new chemical entities correspond to three aliphatic polyketides (1-3), one glycolipid (7), two diterpenes (15,16), two steroids (24,25), one triterpenoid saponin (40), and 17 conotoxins (49)(50)(51)(52)(53)(54)(55)(56)(57)(58)(59)(60)(61)(62)(63)(64)(65). Figure 15 displays the overall biogenetic distribution of the reported compounds.…”