title: Carotenoid Biosynthesis in Calothrix sp. 336/3: Composition of Carotenoids on Full Medium, During Diazotrophic Growth and After Long-Term H2 Photoproduction.
abstract: The carotenoid composition of the filamentous heterocystous N2-fixing cyanobacterium Calothrix sp. 336/3 was investigated under three conditions: in full medium (non-diazotrophic growth); in the absence of combined nitrogen (diazotrophic growth); and after long-term H2photoproduction (diazotrophic medium and absence of nitrogen in the atmosphere). Anabaena sp. PCC 7120 and its ΔhupL mutant with disrupted uptake hydrogenase were used as reference strains. Analysis of identified carotenoids and enzymes involved in carotenogenesis showed the presence of three distinct biosynthetic pathways in Calothrix sp. 336/3. The first one is directed towards biosynthesis of myxoxanthophylls, such as myxol 2'-methylpentoside and 2-hydroxymyxol 2'-methylpentoside. The second pathway results in production of hydroxylated carotenoids, such as zeaxanthin, caloxanthin and nostoxanthin, and the last pathway is responsible for biosynthesis of echinenone and hydroxylated forms of ketocarotenoids, such as 3'-hydroxyechinenone and adonixanthin. We found that carotenogenesis in filamentous heterocystous cyanobacteria varies depending on the nitrogen status of the cultures, with significant accumulation of echinenone during diazotrophic growth at the expense of β-carotene. Under the severe N deficiency and high CO2supply, which leads to efficient H2photoproduction, cyanobacteria degrade echinenone and β-carotene, and accumulate glycosylated and hydroxylated carotenoids, such as myxol (or ketomyxol) 2'-methylpentosides, 3'-hydroxyechinenone and zeaxanthin. We suggest that the stability of the photosynthetic apparatus in Calothrix sp. 336/3 cells under N deficiency and high carbon conditions, which also appeared as the partial recovery of the pigment composition by the end of the long-term (∼1 month) H2photoproduction process, might be mediated by a high content of hydroxycarotenoids.
authors: Molecular Plant Biology, Department of Biochemistry, University of Turku, Turku, Finland.
authors: Sergey
authors: S
authors: Kosourov
authors: Molecular Plant Biology, Department of Biochemistry, University of Turku, Turku, Finland.
authors: Gayathri
authors: G
authors: Murukesan
authors: Division of Microbiology and Biotechnology, Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland.
authors: Jouni
authors: J
authors: Jokela
authors: Molecular Plant Biology, Department of Biochemistry, University of Turku, Turku, Finland allahve@utu.fi.
authors: Yagut
authors: Y
authors: Allahverdiyeva
mesh_terms: D053898:Biosynthetic Pathways / Q000235:genetics / Q000528:radiation effects*; D002338:Carotenoids / Q000096:biosynthesis*; D002851:Chromatography, High Pressure Liquid; D003470:Culture Media; D000458:Cyanobacteria / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism / Q000528:radiation effects*; D005798:Genes, Bacterial; D006859:Hydrogen / Q000378:metabolism*; D008027:Light; D009586:Nitrogen Fixation / Q000528:radiation effects*; D010860:Pigments, Biological / Q000378:metabolism; D013057:Spectrum Analysis; D013997:Time Factors
chemical_list: D003470:Culture Media; D010860:Pigments, Biological; D002338:Carotenoids; D006859:Hydrogen
keywords: Carotenogenic genes; Carotenoid biosynthesis; Diazotrophic growth; Hydrogen photoproduction; Oxidative stress; Photoinhibition