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Evidence of Accelerated Evolution and Ectodermal-Specific Expression of Presumptive BDS Toxin cDNAs from Anemonia viridis
Laboratory of Molecular Ecology and Biotechnology, National Research Council, Institute for Marine and Coastal Environment (IAMC-CNR), Detached Unit of Capo Granitola, Torretta Granitola 91021, Trapani, Italy
Institute for Environmental Protection and Research—ISPRA, Palermo 90143, Italy
National Research Council, Institute for Marine and Coastal Environment (IAMC-CNR), Calata Porta di Massa, Napoli 80133, Italy
* Author to whom correspondence should be addressed.
Received: 21 August 2013; in revised form: 10 September 2013 / Accepted: 13 September 2013 / Published: 30 October 2013
Abstract: Anemonia viridis is a widespread and extensively studied Mediterranean species of sea anemone from which a large number of polypeptide toxins, such as blood depressing substances (BDS) peptides, have been isolated. The first members of this class, BDS-1 and BDS-2, are polypeptides belonging to the β-defensin fold family and were initially described for their antihypertensive and antiviral activities. BDS-1 and BDS-2 are 43 amino acid peptides characterised by three disulfide bonds that act as neurotoxins affecting Kv3.1, Kv3.2 and Kv3.4 channel gating kinetics. In addition, BDS-1 inactivates the Nav1.7 and Nav1.3 channels. The development of a large dataset of A. viridis expressed sequence tags (ESTs) and the identification of 13 putative BDS-like cDNA sequences has attracted interest, especially as scientific and diagnostic tools. A comparison of BDS cDNA sequences showed that the untranslated regions are more conserved than the protein-coding regions. Moreover, the KA/KS ratios calculated for all pairwise comparisons showed values greater than 1, suggesting mechanisms of accelerated evolution. The structures of the BDS homologs were predicted by molecular modelling. All toxins possess similar 3D structures that consist of a triple-stranded antiparallel β-sheet and an additional small antiparallel β-sheet located downstream of the cleavage/maturation site; however, the orientation of the triple-stranded β-sheet appears to differ among the toxins. To characterise the spatial expression profile of the putative BDS cDNA sequences, tissue-specific cDNA libraries, enriched for BDS transcripts, were constructed. In addition, the proper amplification of ectodermal or endodermal markers ensured the tissue specificity of each library. Sequencing randomly selected clones from each library revealed ectodermal-specific expression of ten BDS transcripts, while transcripts of BDS-8, BDS-13, BDS-14 and BDS-15 failed to be retrieved, likely due to under-representation in our cDNA libraries. The calculation of the relative abundance of BDS transcripts in the cDNA libraries revealed that BDS-1, BDS-3, BDS-4, BDS-5 and BDS-6 are the most represented transcripts.
Keywords: Anemonia viridis; BDS peptides; accelerated evolution; molecular modelling; tissue-specific libraries; gene expression pattern
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Nicosia, A.; Maggio, T.; Mazzola, S.; Cuttitta, A. Evidence of Accelerated Evolution and Ectodermal-Specific Expression of Presumptive BDS Toxin cDNAs from Anemonia viridis. Mar. Drugs 2013, 11, 4213-4231.
Nicosia A, Maggio T, Mazzola S, Cuttitta A. Evidence of Accelerated Evolution and Ectodermal-Specific Expression of Presumptive BDS Toxin cDNAs from Anemonia viridis. Marine Drugs. 2013; 11(11):4213-4231.
Nicosia, Aldo; Maggio, Teresa; Mazzola, Salvatore; Cuttitta, Angela. 2013. "Evidence of Accelerated Evolution and Ectodermal-Specific Expression of Presumptive BDS Toxin cDNAs from Anemonia viridis." Mar. Drugs 11, no. 11: 4213-4231.