title: Comparative analyses of lipidomes and transcriptomes reveal a concerted action of multiple defensive systems against photooxidative stress in Haematococcus pluvialis.
abstract: Haematococcus pluvialis cells predominantly remain in the macrozooid stage under favourable environmental conditions but are rapidly differentiated into haematocysts upon exposure to various environmental stresses. Haematocysts are characterized by massive accumulations of astaxanthin sequestered in cytosolic oil globules. Lipidomic analyses revealed that synthesis of the storage lipid triacylglycerol (TAG) was substantially stimulated under high irradiance. Simultaneously, remodelling of membrane glycerolipids occurred as a result of dramatic reductions in chloroplast membrane glycolipids but remained unchanged or declined slightly in extraplastidic membrane glycerolipids. De novo assembly of transcriptomes revealed the genomic and metabolic features of this unsequenced microalga. Comparative transcriptomic analysis showed that so-called resting cells (haematocysts) may be more active than fast-growing vegetative cells (macrozooids) regarding metabolic pathways and functions. Comparative transcriptomic analyses of astaxanthin biosynthesis suggested that the non-mevalonate pathway mediated the synthesis of isopentenyl diphosphate, as the majority of genes involved in subsequent astaxanthin biosynthesis were substantially up-regulated under high irradiance, with the genes encoding phytoene synthase, phytoene desaturase, and β-carotene hydroxylase identified as the most prominent regulatory components. Accumulation of TAG under high irradiance was attributed to moderate up-regulation of de novo fatty acid biosynthesis at the gene level as well as to moderate elevation of the TAG assembly pathways. Additionally, inferred from transcriptomic differentiation, an increase in reactive oxygen species (ROS) scavenging activity, a decrease in ROS production, and the relaxation of over-reduction of the photosynthetic electron transport chain will work together to protect against photooxidative stress in H. pluvialis under high irradiance.
authors.affiliation: Department of Life Science, Research Institute for Natural Science, Hanyang University, Seoul, 133-791, South Korea.
authors.forename: Yunho
authors.initials: Y
authors.lastname: Gwak
authors.affiliation: Department of Bioscience and Biotechnology, Konkuk University, Seoul, 143-701, South Korea.
authors.forename: Yong-sic
authors.initials: YS
authors.lastname: Hwang
authors.affiliation: College of Technology and Innovation, Arizona State University, Mesa, AZ 85212, USA.
authors.forename: Baobei
authors.initials: B
authors.lastname: Wang
authors.affiliation: Department of Life Science, Research Institute for Natural Science, Hanyang University, Seoul, 133-791, South Korea.
authors.forename: Minju
authors.initials: M
authors.lastname: Kim
authors.affiliation: Department of Life Science, Research Institute for Natural Science, Hanyang University, Seoul, 133-791, South Korea.
authors.forename: Jooyeon
authors.initials: J
authors.lastname: Jeong
authors.affiliation: Department of Biotechnology, Institute of Industrial Biotechnology, Inha University, Incheon, 402-751, South Korea.
authors.forename: Choul-Gyun
authors.initials: CG
authors.lastname: Lee
authors.affiliation: Center for Microalgal Biotechnology and Biofuels, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei 430072, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Hu
authors.affiliation: College of Technology and Innovation, Arizona State University, Mesa, AZ 85212, USA esjin@hanyang.ac.kr Danxiang.Han@asu.edu.
authors.forename: Danxiang
authors.initials: D
authors.lastname: Han
authors.affiliation: Department of Life Science, Research Institute for Natural Science, Hanyang University, Seoul, 133-791, South Korea esjin@hanyang.ac.kr Danxiang.Han@asu.edu.
authors.forename: EonSeon
authors.initials: E
authors.lastname: Jin
mesh_terms: D000460:Chlorophyta / Q000378:metabolism* / Q000528:radiation effects; D050356:Lipid Metabolism; D058977:Molecular Sequence Annotation; D018384:Oxidative Stress; D017422:Sequence Analysis, DNA; D013472:Sunlight; D059467:Transcriptome; D024341:Xanthophylls / Q000096:biosynthesis
chemical_list: D024341:Xanthophylls; C005948:astaxanthine
keywords: Astaxanthin; high irradiance; lipidome; photooxidative stress; transcriptome; triacylglycerol.