title: Photosynthetic responses of Oryza sativa L. seedlings to cadmium stress: physiological, biochemical and ultrastructural analyses.
abstract: In the present study, photosynthetic responses induced by cadmium stress in chlorophyll biosynthesis, photochemical activities, the stability of thylakoid membranes chlorophyll-protein complexes and the chloroplast ultrastructure of the cereal crop Oryza sativa L. were characterized. Cadmium inhibited the biosynthesis of chlorophyll by interfering with activity of δ-aminolevulinic acid dehydratase in the rice seedlings. For the photochemical activities analyses, the extent of the decrease in photosystem II activity was much greater than that in the PS I activity. The variations in the chlorophyll a fluorescence parameters also indicated that cadmium toxicity drastically affected the photochemistry of PS II. Biochemical analyses by BN-PAGE and protein immunoblot showed that cadmium toxicity considerably affected the stability of PS II-core, cytb 6 /f, RuBisCO, PSI + LHCI and LHCII (Trimeric). We observed the rate of the thylakoid membranes protein degradation, was mainly at the level of RbcL, PsaA, Lhca1 and D1. In addition, the damages to chloroplast structure and thylakoid stacking analyzed by transmission electron microscopy were indicative of general disarray in the photosynthetic functions exerted by cadmium toxicity. These results are valuable for understanding the biological consequences of heavy metals contamination particularly in soils devoted to organic agriculture.
authors.affiliation: Jiangsu Key Laboratory of Biodiversity and Biotechnology, Life Sciences College, Nanjing Normal University, Nanjing, 210023, China.
authors.forename: Yuwen
authors.initials: Y
authors.lastname: Wang
authors.forename: Xiaohan
authors.initials: X
authors.lastname: Jiang
authors.forename: Kang
authors.initials: K
authors.lastname: Li
authors.forename: Min
authors.initials: M
authors.lastname: Wu
authors.forename: Rufeng
authors.initials: R
authors.lastname: Zhang
authors.forename: Lu
authors.initials: L
authors.lastname: Zhang
authors.forename: Guoxiang
authors.initials: G
authors.lastname: Chen
mesh_terms: D002104:Cadmium / Q000494:pharmacology*; D002734:Chlorophyll / Q000096:biosynthesis; D002736:Chloroplasts / Q000187:drug effects / Q000648:ultrastructure*; D012275:Oryza / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism* / Q000648:ultrastructure; D018384:Oxidative Stress / Q000187:drug effects*; D010788:Photosynthesis / Q000187:drug effects*; D045331:Photosystem I Protein Complex / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000378:metabolism; D036226:Seedlings / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism
chemical_list: D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D002104:Cadmium; D002734:Chlorophyll