Metabolismo de porfirinóides em poliquetas marinhos: Da ecologia à biotecnologia

Project POLLUX will explore the metabolism of porphyrinoids or related tetrapyrroles in Polychaeta by comparing ecology, pigment signatures and associated molecular networks between three hallmark intertidal species. In the aftermath of our previous research, four hypotheses set the foundations for the proposal: Hypothesis 1. The metabolism of tetrapyrroles is an adaptive feature, which means that it can hold significant inter-specific variation driven by environment and ecology. In intertidal Polychaeta, exposure to UV, biofoulants and aquatic or terrestrial predators, for instance, are major selective pressures. Hypothesis 2. Most porphyrinoids in the target species are haem-derived, endogenous or synthesised de novo from ingested haem proteins, complementing or replacing melanins and other common pigments. Hypothesis 3. Some porphyrinoids are photosensitive and can generate ROS when exposed to light in the presence of oxygen. This ability may enable a light-sensing arrangement independent from the nervous system that ultimately promotes negative phototaxis. Hypothesis 4. These pigments partake in the chemical defence against predators and parasites. Either by light-mediated toxicity or other mechanisms, they can have an important role in organisms with relatively simple immune systems. Our paradigm is to develop a sampling strategy that restrains parameters to isolate causal networks, or, as contingency, develop an array of controlled bioassays. Consequently, we opted for three sympatric species of intertidal Polychaeta belonging to distinct families: Hediste diversicolor (Nereididae), Glycera alba (Glyceridae) and Mysta (Eteone) picta (Phyllodocidae). They have similar habitats, though, namely the sandy or sandy-muddy intertidal flats of the Tagus and Sado estuaries, W Portugal (Annex, Fig. 1). Mysta also became a choice for being a phyllodocid like Eulalia, which enables a direct comparison with its rocky intertidal sibling. We are familiar with collecting, rearing and essential anatomy of all species[11]. Besides commonness, the choice of target species relates to: i) they are at least opportunistic predators, which means that most tetrapyrroles (endogenous or not) are likely haem- and not chlorophyll-related (i.e. chlorins and pheophorbides); ii) even though their ecological niches overlap, they have distinct anatomical and behavioural traits, like the burrowing behaviour of Hediste and Glycera but not of Mysta; and iii) their different pigmentation (Annex, Fig. 2), from the reddish Glycera (bloodworms) to the brownish Mysta and the variable colours of Hediste that have been linked to a wide range of pigments, from endogenous porphyrinoids to carotenoids[2]. In turn, Glycera‘s pigmentation has been attributed to haemoglobins[12], but details on haem breakdown are absent. Altogether, the novel aspects of our proposal are summarised in four main objectives: 1) Locate, identify and characterise the main porphyrinoid pigments in target species and infer on their adaptive value for the study species. 2) Identify the genes and networks of genes involved in porphyrin metabolism, position them in the evolution of Annelida and Eumetazoa and compare them functionally and phylogenetically. 3) Assess how season-related environmental challenge modulates porphyrin metabolism pathways and how such changes correlate to fitness and vulnerability. 4) Explore the biopharmacological properties of porphyrinoids from the target species.