title: Whole-cell response of the pennate diatom Phaeodactylum tricornutum to iron starvation.
abstract: Marine primary productivity is iron (Fe)-limited in vast regions of the contemporary oceans, most notably the high nutrient low chlorophyll (HNLC) regions. Diatoms often form large blooms upon the relief of Fe limitation in HNLC regions despite their prebloom low cell density. Although Fe plays an important role in controlling diatom distribution, the mechanisms of Fe uptake and adaptation to low iron availability are largely unknown. Through a combination of nontargeted transcriptomic and metabolomic approaches, we have explored the biochemical strategies preferred by Phaeo dactylum tricornutum at growth-limiting levels of dissolved Fe. Processes carried out by components rich in Fe, such as photosynthesis, mitochondrial electron transport, and nitrate assimilation, were down-regulated. Our results show that this retrenchment is compensated by nitrogen (N) and carbon (C) reallocation from protein and carbohydrate degradation, adaptations to chlorophyll biosynthesis and pigment metabolism, removal of excess electrons by mitochondrial alternative oxidase (AOX) and non-photochemical quenching (NPQ), and augmented Fe-independent oxidative stress responses. Iron limitation leads to the elevated expression of at least three gene clusters absent from the Thalassiosira pseudonana genome that encode for components of iron capture and uptake mechanisms.
authors.affiliation: Centre National de la Recherche Scientifique Unite Mixte de Recherche 8186, Dept of Biology, Ecole Normale Supérieure, 46 rue d'Ulm, 75005 Paris, France.
authors.forename: Andrew E
authors.initials: AE
authors.lastname: Allen
authors.forename: Julie
authors.initials: J
authors.lastname: Laroche
authors.forename: Uma
authors.initials: U
authors.lastname: Maheswari
authors.forename: Markus
authors.initials: M
authors.lastname: Lommer
authors.forename: Nicolas
authors.initials: N
authors.lastname: Schauer
authors.forename: Pascal J
authors.initials: PJ
authors.lastname: Lopez
authors.forename: Giovanni
authors.initials: G
authors.lastname: Finazzi
authors.forename: Alisdair R
authors.initials: AR
authors.lastname: Fernie
authors.forename: Chris
authors.initials: C
authors.lastname: Bowler
mesh_terms: D002241:Carbohydrates / Q000737:chemistry; D002244:Carbon / Q000737:chemistry; D002734:Chlorophyll / Q000737:chemistry; D017377:Diatoms / Q000235:genetics* / Q000378:metabolism*; D015536:Down-Regulation; D016678:Genome; D007501:Iron / Q000737:chemistry / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism; D024101:Mitochondrial Proteins; D008954:Models, Biological; D005810:Multigene Family; D009584:Nitrogen / Q000737:chemistry; D009792:Oceans and Seas; D010088:Oxidoreductases / Q000737:chemistry; D010777:Photochemistry / Q000379:methods; D010858:Pigmentation; D010940:Plant Proteins; D000099188:Alternative Oxidase
chemical_list: D002241:Carbohydrates; D002244:Carbon; D002734:Chlorophyll; D007501:Iron; D024101:Mitochondrial Proteins; D009584:Nitrogen; D010088:Oxidoreductases; D010940:Plant Proteins; D000099188:Alternative Oxidase