title: Essential Role of Acyl-ACP Synthetase in Acclimation of the Cyanobacterium Synechococcus elongatus Strain PCC 7942 to High-Light Conditions.
abstract: Most organisms capable of oxygenic photosynthesis have an aas gene encoding an acyl-acyl carrier protein synthetase (Aas), which activates free fatty acids (FFAs) via esterification to acyl carrier protein. Cyanobacterial aas mutants are often used for studies aimed at photosynthetic production of biofuels because the mutation leads to intracellular accumulation of FFAs and their secretion into the external medium, but the physiological significance of the production of FFAs and their recycling involving Aas has remained unclear. Using an aas-deficient mutant of Synechococcus elongatus strain PCC 7942, we show here that remodeling of membrane lipids is activated by high-intensity light and that the recycling of FFAs is essential for acclimation to high-light conditions. Unlike wild-type cells, the mutant cells could not increase their growth rate as the light intensity was increased from 50 to 400 µmol photons m(-2) s(-1), and the high-light-grown mutant cells accumulated FFAs and the lysolipids derived from all the four major classes of membrane lipids, revealing high-light-induced lipid deacylation. The high-light-grown mutant cells showed much lower PSII activity and Chl contents as compared with the wild-type cells or low-light-grown mutant cells. The loss of Aas accelerated photodamage of PSII but did not affect the repair process of PSII, indicating that PSII is destabilized in the mutant. Thus, Aas is essential for acclimation of the cyanobacterium to high-light conditions. The relevance of the present finding s to biofuel production using cyanobacteria is discussed.
authors.affiliation: Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, 464-8601 Japan Japan Science and Technology Agency, CREST.
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Takatani
authors.affiliation: Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, 464-8601 Japan.
authors.forename: Kazuhide
authors.initials: K
authors.lastname: Use
authors.affiliation: Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, 464-8601 Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Kato
authors.affiliation: Japan Science and Technology Agency, CREST Institute for Advanced Biosciences, Keio University, Yamagata, 997-0052, Japan Present address: Laboratory for Metabolomics, RIKEN Center for Integrative Medical Sciences, Yokohama, 230-0045 Japan.
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Ikeda
authors.affiliation: Japan Science and Technology Agency, CREST Department of Biological Chemistry, Chubu University, Kasugai, 487-8501 Japan.
authors.forename: Kouji
authors.initials: K
authors.lastname: Kojima
authors.affiliation: Japan Science and Technology Agency, CREST Department of Biological Chemistry, Chubu University, Kasugai, 487-8501 Japan.
authors.forename: Makiko
authors.initials: M
authors.lastname: Aichi
authors.affiliation: Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, 464-8601 Japan Japan Science and Technology Agency, CREST.
authors.forename: Shin-Ichi
authors.initials: S
authors.lastname: Maeda
authors.affiliation: Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, 464-8601 Japan Japan Science and Technology Agency, CREST omata@agr.nagoya-u.ac.jp.
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Omata
mesh_terms: D000064:Acclimatization; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D019730:Carbon-Sulfur Ligases / Q000235:genetics / Q000378:metabolism*; D005230:Fatty Acids, Nonesterified / Q000378:metabolism; D008027:Light; D008563:Membrane Lipids / Q000378:metabolism; D009154:Mutation; D010788:Photosynthesis / Q000502:physiology / Q000528:radiation effects; D045332:Photosystem II Protein Complex / Q000502:physiology / Q000528:radiation effects; D046940:Synechococcus / Q000201:enzymology* / Q000235:genetics / Q000502:physiology / Q000528:radiation effects
chemical_list: D001426:Bacterial Proteins; D005230:Fatty Acids, Nonesterified; D008563:Membrane Lipids; D045332:Photosystem II Protein Complex; D019730:Carbon-Sulfur Ligases; C018749:long-chain-fatty-acid-(acyl-carrier-protein) ligase
keywords: Acyl-ACP synthetase; Biofuel production; Cyanobacteria; High-light acclimation; Photoinhibition of PSII