Transcriptome Sequencing of the Pale Anemones (Exaiptasia diaphana) Revealed Functional Peptide Gene Resources of Sea Anemone

Abstract

Sea anemone venom is a marine drug resource library with pharmacological and biotechnology value, and it contains complex and diverse functional peptide neurotoxins. However, the venom components of only a limited number of sea anemone species have been globally evaluated by transcriptomics and proteomics. In this study, 533 putative protein as well as peptide toxin sequences were found on a large scale from dissimilar developmental stages of sea anemone Exaiptasia diaphana, which can be divided into 75 known superfamilies according to the predicted functions. Among them, the proportion of protein is 72.98%, and its main families are metalloproteases, chymotrypsinogen like, collagen, pancreatic lipase-associated protein like, and G-protein coupled receptor, while the proportion of peptides is 27.02%, and main families are ShK domain, thrombin, Kunitz-type, defensin, as well as insulin-like peptide. Finally, typical anemone peptide neurotoxins were screened, and the 3D structure and pharmacological activity of these anemone peptide neurotoxins were predicted by homology modeling. We elucidate on a valuable high-throughput approach for obtaining sea anemone proteins and peptides. Our findings form the basis for targeted studies on the diversity as well as pharmacological effects of sea anemone peptide neurotoxins.

Diversity analysis of sea anemone peptide toxins in different tissues of Heteractis crispa based on transcriptomics

“…Herein, the proportion of identified proteins and peptide toxins is significantly different from previous studies. For example, the proportion of peptide sequences (9%) in sea anemone Stichodactyla haddoni 32 and Exaiptasia diaphana 40 , was significantly lower than the proportion of protein sequences (91%) in our study. The relatively low proportion of peptides in the entire transcriptome of sea anemones can be attributed to the high concentration of protein in the column and mesenterial filaments.…”

“…In addition, the peptide constituents were shown to align with the ShKT domain, β-defensin, and Kunitz-type. In general, comparable findings were noted in transcriptome data obtained from various sea anemones 32 , 33 , 40 . The protein component metalloproteinases were highly expressed in the tentacles and the mesenterial filaments, with lower expression levels in the column than in ShKT domain.…”

“…Many cysteines exist in sea anemone peptide toxins, and cysteine structural scaffolds are diverse. According to our previously proposed classification method 39 , 40 , cysteine patterns of these 93 peptides were split into eight broad categories and several subcategories (Fig. 4 ).…”

“…HTS technology has been applied to multiple venom components of sea anemones 39 , including Exaiptasia diaphana, Nematostella vectensis, Oulactis sp., Anemonia sulcata, Megalactis griffithsi, Epiactis japonicus, Exaiptasia pallida, Anthopleura dowii, and Stichodactyla haddoni 30 , 32 , 33 , 40 , 107 – 113 . The HTS and bioinformatics techniques have been used to determine venom assemblage in tentacles, column, and mesenterial filaments for three species of sea anemone: H. crispa, Anemonia sulcata, and Megalactis griffithsi.…”

Novel technologies uncover novel ‘anti’-microbial peptides in Hydra shaping the species-specific microbiome

“…However, one AMP family, the defensins [35], appears to be omnipresent in the animal kingdom, in plants and fungi. Numerous defensin genes were in silico predicted from the genomes of Cnidaria as well [36][37][38] and few of them were empirically validated [39]. However, no members of the defensin family have been described in Hydra so far.…”