Abstract
Ovothiol, isolated from marine invertebrate eggs, is considered one of the most powerful antioxidant with potential for drug development. However, its biological functions in marine organisms still represent a matter of debate. In sea urchins, the most accepted view is that ovothiol protects the eggs by the high oxidative burst at fertilization. In this work we address the role of ovothiol during sea urchin development to give new insights on ovothiol biosynthesis in metazoans. The gene involved in ovothiol biosynthesis OvoA was identified in Paracentrotus lividus genome (PlOvoA). PlOvoA embryo expression significantly increased at the pluteus stage and was up-regulated by metals at concentrations mimicking polluted sea-water and by cyclic toxic algal blooms, leading to ovothiol biosynthesis. In silico analyses of the PlOvoA upstream region revealed metal and stress responsive elements. Structural protein models highlighted conserved active site residues likely responsible for ovothiol biosynthesis. Phylogenetic analyses indicated that OvoA evolved in most marine metazoans and was lost in bony vertebrates during the transition from the aquatic to terrestrial environment. These results highlight the crucial role of OvoA in protecting embryos released in seawater from environmental cues, thus allowing the survival under different conditions.
Highlights
Is a component of adenochrome, the iron-binding protein in Octopus vulgaris[20,21], and of imbricatine, an alkaloid produced by the sea star Dermasterias imbricate[22]
The OvoA genes in the sea urchins P. lividus and S. purpuratus genomes were identified by tblastx using as sequence query the previously characterized OvoA of E. tasmaniensis and T. cruzi
We investigated functional and evolutionary aspects related to the gene and the enzyme responsible for the biosynthesis of ovothiol, the methylated thiohistidine, first isolated in sea urchin eggs[5]
Summary
Is a component of adenochrome, the iron-binding protein in Octopus vulgaris[20,21], and of imbricatine, an alkaloid produced by the sea star Dermasterias imbricate[22]. The enzyme which catalyzes the first step of ovothiol biosynthesis, 5‐histidylcysteine sulfoxide synthase (OvoA), recently characterized from the bacterium Erwinia tasmaniensis and the pathogenic protist Trypanosoma cruzi[26], has been proposed as a target of anti-infective therapy. This enzyme is an iron (II) dependent sulfoxide synthase, which catalyzes the S-conjunction of cysteine with histidine in the presence of molecular oxygen and S-adenosyl methionine. The aim of the present work is to address the biological role of OvoA in marine metazoans To this aim, sea urchins represent exceptional models for evolutionary, ecotoxicological, and developmental biology studies. Evolutionary analysis of OvoA in metazoans has allowed us to hypothesize the involvement of ovothiol in protecting eggs and embryos released in the seawater column from environmental cues
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