Search Results (4)

The hydrocoral Millepora complanata (fire coral) plays a critical role in reef structure and relies on a symbiotic relationship with Symbiodiniaceae algae. Environmental stressors derived from climate change, such as UV radiation and elevated temperatures, disrupt this symbiosis, leading to bleaching and threatening reef survival. To gain insight into the thermal stress response of this reef-building hydrocoral, this study investigates the proteomic response of M. complanata to bleaching during the 2015–2016 El Niño event. Fragments from non-bleached and bleached colonies of the hydrocoral M. complanata were collected from a coral reef in the Mexican Caribbean, and proteomic extracts were analyzed using nano-liquid chromatography–tandem mass spectrometry (nano-LC-MS/MS). Uni- and multivariate analyses were applied to identify significant differences in protein abundance. A total of 52 proteins showed differential abundance, including 24 that showed increased expression and 28 whose expression decreased in bleached fragments. Differentially abundant proteins were associated with amino acid biosynthesis, carbohydrate metabolism, cytoskeleton organization, DNA repair, extracellular matrix composition, redox homeostasis, and protein modification. These molecular alterations reflect critical physiological adaptations that may influence stress sensitivity or tolerance in hydrocorals. The findings indicate that heat stress induces molecular responses involving protein refolding, enhanced vesicular transport, cytoskeletal reorganization, and modulation of redox activity. This contributes to a deeper understanding of the molecular mechanisms underlying bleaching in reef-building hydrozoans and broadens current knowledge beyond the more extensively studied anthozoan corals. Full article

To date, few studies have been carried out aimed at characterizing the toxins synthesized by hydrocorals of the genus Millepora. The purpose of this study was to explore the toxin diversity and antibacterial activity of the “fire coral” M. complanata using a transcriptomic data mining approach. In addition, the cytolytic and antibacterial activities of the M. complanata nematocyst proteome were experimentally confirmed. Cytolysins were predicted from the transcriptome by comparing against the Animal Toxin Annotation Project database, resulting in 190 putative toxins, including metalloproteases, hemostasis-impairing toxins, phospholipases, among others. The M. complanata nematocyst proteome was analyzed by 1D and 2D electrophoresis and zymography. The zymograms showed different zones of cytolytic activity: two zones of hemolysis at ~25 and ~205 kDa, two regions corresponding to phospholipase A2 (PLA2) activity around 6 and 25 kDa, and a proteolytic zone was observed between 50 and 205 kDa. The hemolytic activity of the proteome was inhibited in the presence of PLA2 and proteases inhibitors, suggesting that PLA2s, trypsin, chymotrypsin, serine-proteases, and matrix metalloproteases are responsible for the hemolysis. On the other hand, antimicrobial peptide sequences were retrieved from their transcripts with the amPEPpy software. This analysis revealed the presence of homologs to SK84, cgUbiquitin, Ubiquicidin, TroTbeta4, SPINK9-v1, and Histone-related antimicrobials in the transcriptome of this cnidarian. Finally, by employing disk diffusion and microdilution assays, we found that the nematocyst peptidome of M. complanata showed inhibitory activity against both Gram-positive and Gram-negative bacteria including S. enteritidis, P. perfectomarina, E. coli, and C. xerosis, among others. This is the first transcriptomic data mining analysis to explore the diversity of the toxins synthesized by an organism of the genus Millepora. Undoubtedly, this work provides information that will broaden our general understanding of the structural richness of cnidarian toxins. Full article

Coral bleaching caused by global warming has resulted in massive damage to coral reefs worldwide. Studies addressing the consequences of elevated temperature have focused on organisms of the class Anthozoa, and up to now, there is little information regarding the mechanisms by which reef forming Hydrozoans face thermal stress. In this study, we carried out a comparative analysis of the soluble proteome and the cytolytic activity of unbleached and bleached Millepora complanata (“fire coral”) that inhabited reef colonies exposed to the 2015–2016 El Niño-Southern Oscillation in the Mexican Caribbean. A differential proteomic response involving proteins implicated in key cellular processes, such as glycolysis, DNA repair, stress response, calcium homeostasis, exocytosis, and cytoskeleton organization was found in bleached hydrocorals. Four of the proteins, whose levels increased in bleached specimens, displayed sequence similarity to a phospholipase A2, an astacin-like metalloprotease, and two pore forming toxins. However, a protein, which displayed sequence similarity to a calcium-independent phospholipase A2, showed lower levels in bleached cnidarians. Accordingly, the hemolytic effect of the soluble proteome of bleached hydrocorals was significantly higher, whereas the phospholipase A2 activity was significantly reduced. Our results suggest that bleached M. complanata is capable of increasing its toxins production in order to balance the lack of nutrients supplied by its symbionts. Full article