Figure 1.
Molecular phylogeny of Pseudo-nitzschia species.
Maximum Likelihood tree constructed with rbcL (A) and LSU (B) sequences. The strains in bold have been analysed for oxylipin production. The position specificity of the LOX activity detected for the different strains and the still unidentified compounds are mapped with different colours on the trees.
Figure 2.
Major EPA-derived oxylipins characterized in Pseudo-nitzschia species during this study.
Compounds have been identified on the basis of comparison of primary analytical indicators (retention time, UV spectrum, molecular weight and mass/mass fragmentation) with those experimentally determined or calculated in agreement with [21].
Figure 3.
Lipoxygenase positional specificity in the genus Pseudo-nitzschia.
Identification is inferred on MS/MS fragmentation of hydroxy-epoxy eicosatetraenoic acids (HEpETEs) derived from LOX-mediated metabolism of EPA. (a) EPA and position of LOX oxidation. (b) Biochemical mechanism leading to specific transformation of primary LOX product (hydroperoxy-eicosapentaenoic acid, HpEPE) to HEpETE. For simplicity, the polyunsaturated chain of EPA is represented by the 1,3-pentadiene moiety that undergoes to enzymatic oxidation. R1 and R2 are variable alkyl residues to complement the structure of EPA. (c) Diagnostic ions of different HEpETEs generated by MS/MS fragmentation.
Figure 4.
Heat map representation of oxylipin signals in the Pseudo-nitzschia strains.
A semi-quantitative estimate of the individual oxylipins (rows) recorded in the analyzed strains (columns). Color scale represents the ratio between peak areas of individual oxylipins and internal standard (see Materials and Methods). Suffix ‘/r’ followed by number indicates biological replicates of the same strain. Chemical abbreviations are in agreement with Figure 2.