Combined Effects of Diatom-Derived Oxylipins on the Sea Urchin Paracentrotus lividus

Abstract

Oxylipins are diatom-derived secondary metabolites, deriving from the oxidation of polyunsatured fatty acids that are released from cell membranes after cell damage or senescence of these single-celled algae. Previous results revealed harmful toxic effects of polyunsaturated aldehydes (PUAs) and hydroxyacids (HEPEs) on sea urchin Paracentrotus lividus embryonic development by testing individual compounds and mixtures of the same chemical group. Here, we investigated the combined effects of these compounds on sea urchin development at the morphological and molecular level for the first time. Our results demonstrated that oxylipin mixtures had stronger effects on sea urchin embryos compared with individual compounds, confirming that PUAs induce malformations and HEPEs cause developmental delay. This harmful effect was also confirmed by molecular analysis. Twelve new genes, involved in stress response and embryonic developmental processes, were isolated from the sea urchin P. lividus; these genes were found to be functionally interconnected with 11 genes already identified as a stress response of P. lividus embryos to single oxylipins. The expression levels of most of the analyzed genes targeted by oxylipin mixtures were involved in stress, skeletogenesis, development/differentiation, and detoxification processes. This work has important ecological implications, considering that PUAs and HEPEs represent the most abundant oxylipins in bloom-forming diatoms, opening new perspectives in understanding the molecular pathways activated by sea urchins exposed to diatom oxylipins.

Two Benthic Diatoms, Nanofrustulum shiloi and Striatella unipunctata, Encapsulated in Alginate Beads, Influence the Reproductive Efficiency of Paracentrotus lividus by Modulating the Gene Expression

“…These results could indicate that benthic diatoms affect some common molecular pathways by changing the normal biological mechanisms, which, in turn, generate aberrant progenies in sea urchins. Interestingly, several genes followed by RT-qPCR in the present study were previously found to be functionally interconnected [41][42][43]. In particular, Varrella et al [41] showed that both diatoms altered the expression of all genes belonging to the network, except for Alix, whose relative expression was not significant (Figure 6).…”

Multiple Roles of Diatom-Derived Oxylipins within Marine Environments and Their Potential Biotechnological Applications

“…Since marine organisms are normally exposed to LOX products as a whole, very recent studies were conducted to evaluate the potentially negative effect of PUAs and HEPEs mixtures on the sea urchin P. lividus [ 74 , 76 , 78 ]. Specifically, Ruocco et al [ 76 ] showed that, by decreasing PUAs concentrations to one third of those used in individual tests (reported in Varrella et al [ 67 ]), both binary and ternary mixtures were able to induce malformations in a synergic way, with the highest percentage of malformed plutei achieved in the case of 0.5 μM DD plus 1.0 μM HD at 48 hpf.…”

“…The effects of oxylipin combinations on sea urchin embryos were further clarified by testing PUAs plus HEPEs mixtures [ 78 ]. Morphological observations revealed that these mixtures induced a stronger effect, compared to single compounds, with a dose-dependent developmental delay.…”

“…In fact, even if PUAs in individual tests resulted stronger than HEPEs, when in mixtures PUAs + HEPEs the effects of HEPEs diluted those of PUAs. In fact, in the first 48 hpf, oxylipin mixtures only induced developmental delay in sea urchin embryos and no malformed embryos were detected [ 78 ]. Moreover, IPA analysis led to the isolation of twelve new genes that were functionally correlated to eleven genes already identified in previous studies [ 67 , 71 , 73 ].…”

“…Moreover, IPA analysis led to the isolation of twelve new genes that were functionally correlated to eleven genes already identified in previous studies [ 67 , 71 , 73 ]. Real time qPCR analyses revealed that almost all of the genes, belonging to stress and developmental processes were significantly altered (>2-fold) [ 78 ]. Taken together, all these results strongly indicate that the delay observed in the early development of sea urchins exposed to oxylipin mixtures may be due to HEPEs, which act in an irreversible way, targeting many genes involved in skeletogenesis and development/differentiation processes already at the blastula stage.…”