Oxylipin Diversity in the Diatom Family Leptocylindraceae Reveals DHA Derivatives in Marine Diatoms

Abstract

Marine planktonic organisms, such as diatoms, are prospective sources of novel bioactive metabolites. Oxygenated derivatives of fatty acids, generally referred to as oxylipins, in diatoms comprise a highly diverse and complex family of secondary metabolites. These molecules have recently been implicated in several biological processes including intra- and inter-cellular signaling as well as in defense against biotic stressors and grazers. Here, we analyze the production and diversity of C20 and C22 non-volatile oxylipins in five species of the family Leptocylindraceae, which constitute a basal clade in the diatom phylogeny. We report the presence of species-specific lipoxygenase activity and oxylipin patterns, providing the first demonstration of enzymatic production of docosahexaenoic acid derivatives in marine diatoms. The differences observed in lipoxygenase pathways among the species investigated broadly reflected the relationships observed with phylogenetic markers, thus providing functional support to the taxonomic diversity of the individual species.

Comparative Transcriptomic Analysis Uncovers Genes Responsible for the DHA Enhancement in the Mutant Aurantiochytrium sp.

“…The FAS pathway comprised seven or more kinds of desaturases, including ∆12, ∆9, ∆8, ∆6, ∆5, ∆4, and n-3 (e.g., ∆17 and ∆15). However, the activity of desaturase and elongase was not detected in Schizochytrium by 14 C labeling, which implies the existence of a different DHA biosynthesis mechanism in the genus Schizochytrium [56]. The transcriptomic study of the mutant X2 and WT revealed that only one gene encoding desaturase was involved in the FAS pathway; however, the ∆4, ∆6, and ∆12 desaturase genes, which are important for DHA production, were not observed in the present study.…”

“…Eggs naturally contain small amounts of DHA, but new DHA enriched eggs can contain up to 258.2 mg of DHA per egg [11]. Furthermore, marine microalgae including chrysophyta [12], dinoflagellate [13], and diatom [14], are also regarded as a promising alternative as the primary producer of the EPA and DHA in marine food webs. Marine eukaryotes, such as Thraustochytrids [15] and Schizochytrium, with abundant FA contents, have emerged as promising producers of n-3 LC-PUFAs [16].…”

Non-volatile oxylipins can render some diatom blooms more toxic for copepod reproduction

“…One of these compounds, 15S-HEPE, acts similarly to PUAs in that it induces malformations in newlyhatched nauplii and arrests embryogenesis at elevated concentrations (Ianora et al, 2011b). Interestingly, many diatom species seem to produce only these NVOs and not PUAs (Barreiro et al, 2011;Cutignano and Lamari, 2011;d'Ippolito et al, 2009;Fontana et al, 2007;Nanjappa et al, 2014). Similar compounds are also produced by benthic diatoms, where these compounds have been suggested to play a role as foraging kairomones, indicating the presence of abundant food (Jü ttner et al, 2010).…”

Analysis of light quality and assemblage composition on diatom motility and accumulation rate

“…While the molecular mechanisms driving resource partitioning between species are poorly understood, diatom signalling molecules have been found that affect both inter-and intra-cellular processes (Caldwell 2009, Nanjappa et al 2014 or may act as sexual pheromones (Gillard et al 2013). Species-specific releases of molecules affecting cell vitality, such as CNBr (Vanelslander et al 2012), have also been shown to be involved in the formation of algal biofilms.…”