title: Photoprotection vs. Photoinhibition of Photosystem II in Transplastomic Lettuce (Lactuca sativa) Dominantly Accumulating Astaxanthin.
abstract: Transplastomic (chloroplast genome-modified; CGM) lettuce that dominantly accumulates astaxanthin grows similarly to a non-transgenic control with almost no accumulation of naturally occurring photosynthetic carotenoids. In this study, we evaluated the activity and assembly of PSII in CGM lettuce. The maximum quantum yield of PSII in CGM lettuce was <0.6; however, the quantum yield of PSII was comparable with that in control leaves under higher light intensity. CGM lettuce showed a lower ability to induce non-photochemical quenching (NPQ) than the control under various light intensities. The fraction of slowly recovering NPQ in CGM lettuce, which is considered to be photoinhibitory quenching (qI), was less than half that of the control. In fact,1O2generation was lower in CGM than in control leaves under high light intensity. CGM lettuce contained less PSII, accumulated mostly as a monomer in thylakoid membranes. The PSII monomers purified from the CGM thylakoids bound echinenone and canthaxanthin in addition to β-carotene, suggesting that a shortage of β-carotene and/or the binding of carbonyl carotenoids would interfere with the photophysical function as well as normal assembly of PSII. In contrast, high accumulation of astaxanthin and other carbonyl carotenoids was found within the thylakoid membranes. This finding would be associated with the suppression of photo-oxidative stress in the thylakoid membranes. Our observation suggests the importance of a specific balance between photoprotection and photoinhibition that can support normal photosynthesis in CGM lettuce producing astaxanthin.
authors.affiliation: The Osaka City University Advanced Research Institute for Natural Science and Technology (OCARINA), Osaka City University, 3-3-138, Sugimoto, Sumiyoshi-ku, Osaka, 558-8585 Japan ritsuko@ocarina.osaka-cu.ac.jp ifuku@kais.kyoto-u.ac.jp.|Graduate School of Science, Osaka City University, 3-3-138, Sugimoto, Sumiyoshi-ku, Osaka, 558-8585 Japan.|JST, PRESTO, 4-1-8 Honcho Kawaguchi, Saitama, 332-0012 Japan.
authors.forename: Ritsuko
authors.initials: R
authors.lastname: Fujii
authors.affiliation: Graduate School of Science, Osaka City University, 3-3-138, Sugimoto, Sumiyoshi-ku, Osaka, 558-8585 Japan.
authors.forename: Nami
authors.initials: N
authors.lastname: Yamano
authors.affiliation: The Osaka City University Advanced Research Institute for Natural Science and Technology (OCARINA), Osaka City University, 3-3-138, Sugimoto, Sumiyoshi-ku, Osaka, 558-8585 Japan.|Graduate School of Science, Osaka City University, 3-3-138, Sugimoto, Sumiyoshi-ku, Osaka, 558-8585 Japan.|Present address: Department of Applied Chemistry for Environment, Graduate School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda, Hyogo, 669-1337 Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Hashimoto
authors.affiliation: Research Institute for Bioresources and Biotechnology, Ishikawa Prefectural University, 1-308 Suematsu, Nonoichi-Shi Ishikawa, 921-8836 Japan.
authors.forename: Norihiko
authors.initials: N
authors.lastname: Misawa
authors.affiliation: Graduate School of Biostudies, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, 606-8502 Japan ritsuko@ocarina.osaka-cu.ac.jp ifuku@kais.kyoto-u.ac.jp.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Ifuku
mesh_terms: D002499:Centrifugation, Density Gradient; D002734:Chlorophyll / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D054628:Genome, Chloroplast; D018545:Lactuca / Q000235:genetics* / Q000528:radiation effects*; D008027:Light; D010641:Phenotype; D055668:Photochemical Processes / Q000528:radiation effects*; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism / Q000528:radiation effects / Q000648:ultrastructure; D030821:Plants, Genetically Modified; D018087:Plastids / Q000235:genetics* / Q000528:radiation effects / Q000648:ultrastructure; D026082:Singlet Oxygen / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D013696:Temperature; D020524:Thylakoids / Q000378:metabolism / Q000528:radiation effects / Q000648:ultrastructure; D024341:Xanthophylls / Q000378:metabolism
chemical_list: D045332:Photosystem II Protein Complex; D024341:Xanthophylls; D002734:Chlorophyll; D026082:Singlet Oxygen; C005948:astaxanthine
keywords: Astaxanthin; Carbonyl carotenoids; Chloroplast genome modified; Lactuca sativa; PSII; Photoinhibition