Osteococcus tauri plastidic lipid C18-PUFA remodelling involves two plastid-located cytochrome-b5 fused Δ6-desaturases with distinct preferences for both head-group and acyl-chain.
Alteration of fatty-acid unsaturation is a universal response to temperature changes. Marine microalgae display the largest diversity of polyunsaturated fatty-acid (PUFA) whose content notably varies according to temperature. The physiological relevance and the molecular mechanisms underlying these changes are however, still poorly understood. The ancestral green picoalga Ostreococcus tauri displays original lipidic features that combines PUFAs from two distinctive microalgal lineages (Chlorophyceae, Chromista kingdom). In this study, optimized conditions were implemented to unveil early fatty-acid and desaturase transcriptional variations upon chilling and warming. We further functionally characterized the O. tauri ω3-desaturase which is closely related to ω3-desaturases from Chromista species. Our results show that the overall omega-3 to omega-6 ratio is swiftly and reversibly regulated by temperature variations. The proportion of the peculiar 18:5 fatty-acid and temperature are highly and inversely correlated pinpointing the importance of 18:5 temperature-dependent variations across kingdoms. Chilling rapidly and sustainably up-regulated most desaturase genes. Desaturases involved in the regulation of the C18-PUFA pool as well as the Δ5-desaturase appear to be major transcriptional targets. The only ω3-desaturase candidate, related to ω3-desaturases from Chromista species, is localized at chloroplasts in Nicotiana benthamiana and efficiently performs ω3-desaturation of C18-PUFAs in Synechocystis sp. PCC6803. Overexpression in the native host further unveils a broad impact on plastidial and non-plastidial glycerolipids illustrated by the alteration of omega-3/omega-6 ratio in C16-PUFA and VLC-PUFA pools. Global glycerolipid features of the overexpressor recall those of chilling acclimated cells.
Short title: plastidic Δ6-desaturase in the green lineage 15One sentence summary: Osteococcus tauri plastidic lipid C18-PUFA remodelling 16 involves two plastid-located cytochrome-b5 fused Δ6-desaturases with distinct preferences for 17 both head-group and acyl-chain. 18 Footnotes: 19Author Contributions 20 CDG performed the work and analyses on O. tauri (cloning, transgenic screening, TCL, GC-FID, MS/MS); RD performed the work and analyses on N. benthamiana OE 22 (cloning, FAMES analysis); CL performed most of the lipid analyses of 23 O. tauri and N. benthamiana (agro-transformation, HP-TLC, GC-FID); NP performed the 24 work and analysis on Synechocystis (transformation, screening, TCL, GC-FID); SM designed, 25 2 performed and analyzed the photosynthesis experiments; KT performed cloning and qPCR 26 experiments; JeJ performed the work on DES localization and qPCR analyses; JuJ performed 27 MS/MS analyses; JG performed the work on DES localization; IS supervised the work on 28Synechocystis; FD performed and supervised the work on N. benthamiana, helped to organize 29 the MS; FC designed, supervised and performed the research, analyzed the data (O. tauri, N. 30 benthamiana, Synechocystis), wrote the paper. 31The authors responsible for distribution of materials integral to the findings presented in 32 this article in accordance with the policy described in the Instructions for Authors are: 33 Florence Corellou, florence.corellou@u-bordeaux.fr and Iwane Suzuki, 34 iwanes6803@biol.tsukuba.ac.jp concerning Synechocystis PCC 6803 lines. 35 3 ABSTRACT 36 Eukaryotic Δ6-desaturases are microsomal enzymes which balance the synthesis of ω-3 37 and ω-6 C18-polyunsaturated-fatty-acids (PUFA) accordingly to their specificity. In several 38 microalgae, including O. tauri, plastidic C18-PUFA are specifically regulated by 39 environmental cues suggesting an autonomous control of Δ6-desaturation of plastidic PUFA. 40 Sequence retrieval from O. tauri desaturases, highlighted two putative Δ6/Δ8-desaturases 41 sequences clustering, with other microalgal homologs, apart from other characterized Δ-6 42 desaturases. Their overexpression in heterologous hosts, including N. benthamiana and 43 Synechocystis, unveiled their Δ6-desaturation activity and plastid localization. O. tauri lines 44 overexpressing these Δ6-desaturases no longer adjusted their plastidic C18-PUFA amount 45 under phosphate starvation but didn't show any obvious physiological alterations. Detailed 46 lipid analyses from the various overexpressing hosts, unravelled that the substrate features 47 involved in the Δ6-desaturase specificity importantly involved the lipid head-group and likely 48 the non-substrate acyl-chain, in addition to the overall preference for the ω-class of the 49 substrate acyl-chain. The most active desaturase displayed a broad range substrate specificity 50for plastidic lipids and a preference for ω-3 substrates, while the other was selective for ω-6 51 substrates, phosphatidylglycerol and 16:4-galactolipid species specific to the native h...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.