title: The mechanisms by which phenanthrene affects the photosynthetic apparatus of cucumber leaves.
abstract: Phenanthrene is a polycyclic aromatic hydrocarbon (PAH) that is widely distributed in the environment and seriously affects the growth and development of plants. To clarify the mechanisms of the direct effects of phenanthrene on the plant photosynthetic apparatus, we measured short-term phenanthrene-treated cucumber leaves. Phenanthrene inhibited Rubisco carboxylation activity, decreasing photosynthesis rates (Pn). And phenanthrene inhibited photosystem II (PSII) activity, thereby blocking photosynthetic electron transport. The inhibition of the light and dark reactions decreased the photosynthetic electron transport rate (ETR) and increased the excitation pressure (1-qP). Under high light, the maximum photochemical efficiency of photosystem II (Fv/Fm) in phenanthrene-treated cucumber leaves decreased significantly, but photosystem I (PSI) activity (Δ I/Io) did not. Phenanthrene also caused a J-point rise in the OJIP curve under high light, which indicated that the acceptor side of PSII QAto QBelectron transfer was restricted. This was primarily due to the net degradation of D1 protein, which is caused by the accumulation of reactive oxygen species (ROS) in phenanthrene-treated cucumber leaves under high light. This study demonstrated that phenanthrene could directly inhibit photosynthetic electron transport and Rubisco carboxylation activity to decrease net Pn. Under high light, phenanthrene caused the accumulation of ROS, resulting in net increases in D1 protein degradation and consequently causing PSII photoinhibition.
authors.affiliation: State Key Lab of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an, 271018, China.
authors.forename: Liqiao
authors.initials: L
authors.lastname: Jin
authors.affiliation: State Key Lab of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an, 271018, China.
authors.forename: Xingkai
authors.initials: X
authors.lastname: Che
authors.affiliation: State Key Lab of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an, 271018, China.
authors.forename: Zishan
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: State Key Lab of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an, 271018, China.
authors.forename: Yuting
authors.initials: Y
authors.lastname: Li
authors.affiliation: State Key Lab of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an, 271018, China. Electronic address: gaohy@sdau.edu.cn.
authors.forename: Huiyuan
authors.initials: H
authors.lastname: Gao
authors.affiliation: State Key Lab of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an, 271018, China. Electronic address: sjzhao@sdau.edu.cn.
authors.forename: Shijie
authors.initials: S
authors.lastname: Zhao
mesh_terms: D018553:Cucumis sativus / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D004579:Electron Transport; D008027:Light; D010616:Phenanthrenes / Q000378:metabolism / Q000633:toxicity*; D010788:Photosynthesis / Q000187:drug effects*; D045331:Photosystem I Protein Complex / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D012989:Soil Pollutants / Q000633:toxicity*
chemical_list: D010616:Phenanthrenes; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D017382:Reactive Oxygen Species; D012989:Soil Pollutants; C031181:phenanthrene
keywords: D1 protein; PSII photoinhibition; Phenanthrene; Photosynthesis; ROS