title: Analysis of ΔpH and the xanthophyll cycle in NPQ of the Antarctic sea ice alga Chlamydomonas sp. ICE-L.
abstract: Non-photochemical fluorescence quenching (NPQ) is mainly associated with the transthylakoid proton gradient (ΔpH) and xanthophyll cycle. However, the exact mechanism of NPQ is different in different oxygenic photosynthetic organisms. In this study, several inhibitors were used to study NPQ kinetics in the sea ice alga Chlamydomonas sp. ICE-L and to determine the functions of ΔpH and the xanthophyll cycle in the NPQ process. NH4Cl and nigericin, uncouplers of ΔpH, inhibited NPQ completely and zeaxanthin (Z) was not detected in 1 mM NH4Cl-treated samples. Moreover, Z and NPQ were increased in the samples containing N,N'-dicyclohexyl-carbodiimide (DCCD) under low light conditions. We conclude that ΔpH plays a major role in NPQ, and activation of the xanthophyll cycle is related to ΔpH. In dithiothreitol (DTT)-treated samples, no Z was observed and NPQ decreased. NPQ was completely inhibited when NH4Cl was added suggesting that part of the NPQ process is related to the xanthophyll cycle and the remainder depends on ΔpH. Moreover, lutein and β-carotene were also essential for NPQ. These results indicate that NPQ in the sea ice alga Chlamydomonas sp. ICE-L is mainly dependent on ΔpH which affects the protonation of PSII proteins and de-epoxidation of the xanthophyll cycle, and the transthylakoid proton gradient alone can induce NPQ.
authors.affiliation: Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao 266071, China.
authors.forename: Shanli
authors.initials: S
authors.lastname: Mou
authors.forename: Xiaowen
authors.initials: X
authors.lastname: Zhang
authors.forename: Naihao
authors.initials: N
authors.lastname: Ye
authors.forename: Jinlai
authors.initials: J
authors.lastname: Miao
authors.forename: Shaona
authors.initials: S
authors.lastname: Cao
authors.forename: Dong
authors.initials: D
authors.lastname: Xu
authors.forename: Xiao
authors.initials: X
authors.lastname: Fan
authors.forename: Meiling
authors.initials: M
authors.lastname: An
mesh_terms: D000643:Ammonium Chloride / Q000494:pharmacology; D000864:Antarctic Regions; D002696:Chlamydomonas / Q000378:metabolism*; D004024:Dicyclohexylcarbodiimide / Q000494:pharmacology; D005453:Fluorescence; D006863:Hydrogen-Ion Concentration; D014975:Lutein / Q000378:metabolism*; D009550:Nigericin / Q000494:pharmacology; D017785:Photons; D012623:Seawater; D020524:Thylakoids / Q000187:drug effects / Q000378:metabolism; D024341:Xanthophylls / Q000378:metabolism; D065146:Zeaxanthins; D019207:beta Carotene / Q000378:metabolism
chemical_list: D024341:Xanthophylls; D065146:Zeaxanthins; D000643:Ammonium Chloride; D019207:beta Carotene; D004024:Dicyclohexylcarbodiimide; D009550:Nigericin; D014975:Lutein