title: Molecular mechanisms of the coordination between astaxanthin and fatty acid biosynthesis in Haematococcus pluvialis (Chlorophyceae).
abstract: Astaxanthin, a red ketocarotenoid with strong antioxidant activity and high commercial value, possesses important physiological functions in astaxanthin-producing microalgae. The green microalga Haematococcus pluvialis accumulates up to 4% fatty acid-esterified astaxanthin (by dry weight), and is used as a model species for exploring astaxanthin biosynthesis in unicellular photosynthetic organisms. Although coordination of astaxanthin and fatty acid biosynthesis in a stoichiometric fashion was observed in H. pluvialis, the interaction mechanism is unclear. Here we dissected the molecular mechanism underlying coordination between the two pathways in H. pluvialis. Our results eliminated possible coordination of this inter-dependence at the transcriptional level, and showed that this interaction was feedback-coordinated at the metabolite level. In vivo and in vitro experiments indicated that astaxanthin esterification drove the formation and accumulation of astaxanthin. We further showed that both free astaxanthin biosynthesis and esterification occurred in the endoplasmic reticulum, and that certain diacylglycerol acyltransferases may be the candidate enzymes catalyzing astaxanthin esterification. A model of astaxanthin biosynthesis in H. pluvialis was subsequently proposed. These findings provide further insights into astaxanthin biosynthesis in H. pluvialis.
authors.affiliation: Laboratory for Algae Research and Biotechnology, College of Technology and Innovation, Arizona State University, 7001 E. Williams Field Road, Mesa, AZ, 85212, USA.
authors.forename: Guanqun
authors.initials: G
authors.lastname: Chen
authors.forename: Baobei
authors.initials: B
authors.lastname: Wang
authors.forename: Danxiang
authors.initials: D
authors.lastname: Han
authors.forename: Milton
authors.initials: M
authors.lastname: Sommerfeld
authors.forename: Yinghua
authors.initials: Y
authors.lastname: Lu
authors.forename: Feng
authors.initials: F
authors.lastname: Chen
authors.forename: Qiang
authors.initials: Q
authors.lastname: Hu
mesh_terms: D020418:Algal Proteins / Q000378:metabolism / Q000502:physiology; D000460:Chlorophyta / Q000235:genetics / Q000378:metabolism*; D051048:Diacylglycerol O-Acyltransferase / Q000378:metabolism / Q000502:physiology; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004951:Esterification; D005227:Fatty Acids / Q000096:biosynthesis*; D053858:Metabolic Networks and Pathways; D058086:Microalgae / Q000378:metabolism*; D014158:Transcription, Genetic; D024341:Xanthophylls / Q000096:biosynthesis
chemical_list: D020418:Algal Proteins; D005227:Fatty Acids; D024341:Xanthophylls; C005948:astaxanthine; D051048:Diacylglycerol O-Acyltransferase
keywords: Haematococcus pluvialis; acyl CoA diacylglycerol acyltransferase; carotenoid; fatty acid biosynthesis; gene transcription; metabolic coordination; microalgae