title: Nitrate reductase-mediated NO production enhances Cd accumulation in Panax notoginseng roots by affecting root cell wall properties.
abstract: Panax notoginseng (Burk) F. H. Chen is a traditional medicinal herb in China. However, the high capacity of its roots to accumulate cadmium (Cd) poses a potential risk to human health. Although there is some evidence for the involvement of nitric oxide (NO) in mediating Cd toxicity, the origin of Cd-induced NO and its function in plant responses to Cd remain unknown. In this study, we examined NO synthesis and its role in Cd accumulation in P. notoginseng roots. Cd-induced NO production was significantly decreased by application of the nitrate reductase inhibitor tungstate but not the nitric oxide synthase inhibitor L-NAME (N(G)-methyl-l-arginine acetate), indicating that nitrate reductase is the major contributor to Cd-induced NO production in P. notoginseng roots. Under conditions of Cd stress, sodium nitroprusside (SNP, an NO donor) increased Cd accumulation in root cell walls but decreased Cd translocation to the shoot. In contrast, the NO scavenger cPTIO (2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) and tungstate both significantly decreased NO-increased Cd retention in root cell walls. The amounts of hemicellulose 1 and pectin, together with pectin methylesterase activity, were increased with the addition of SNP but were decreased by cPTIO and tungstate. Furthermore, increases or decreases in hemicellulose 1 and pectin contents as well as pectin methylesterase activity fit well with the increased or decreased retention of Cd in the cell walls of P. notoginseng roots. The results suggest that nitrate reductase-mediated NO production enhances Cd retention in P. notoginseng roots by modulating the properties of the cell wall.
authors.affiliation: Faculty of Life Science and Biotechnology, Chenggong Campus, Kunming University of Science and Technology, Kunming 650500, China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Kan
authors.affiliation: Faculty of Life Science and Biotechnology, Chenggong Campus, Kunming University of Science and Technology, Kunming 650500, China.
authors.forename: Wenwei
authors.initials: W
authors.lastname: Wu
authors.affiliation: Faculty of Life Science and Biotechnology, Chenggong Campus, Kunming University of Science and Technology, Kunming 650500, China.
authors.forename: Wenqian
authors.initials: W
authors.lastname: Yu
authors.affiliation: Faculty of Life Science and Biotechnology, Chenggong Campus, Kunming University of Science and Technology, Kunming 650500, China.
authors.forename: Jiarong
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, Mengla, Yunnan 666303, China.
authors.forename: Jin
authors.initials: J
authors.lastname: Xu
authors.affiliation: Soil Science and Plant Nutrition, Faculty of Science, The University of Western Australia, 35 Stirling Highway, Perth, WA 6000, Australia.
authors.forename: Zed
authors.initials: Z
authors.lastname: Rengel
authors.affiliation: Faculty of Life Science and Biotechnology, Chenggong Campus, Kunming University of Science and Technology, Kunming 650500, China.
authors.forename: Limei
authors.initials: L
authors.lastname: Chen
authors.affiliation: Faculty of Life Science and Biotechnology, Chenggong Campus, Kunming University of Science and Technology, Kunming 650500, China.
authors.forename: Xiuming
authors.initials: X
authors.lastname: Cui
authors.affiliation: Faculty of Life Science and Biotechnology, Chenggong Campus, Kunming University of Science and Technology, Kunming 650500, China. Electronic address: chenq0321@163.com.
authors.forename: Qi
authors.initials: Q
authors.lastname: Chen
mesh_terms: D001565:Benzoates / Q000494:pharmacology; D002104:Cadmium / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism*; D002681:China; D007093:Imidazoles / Q000494:pharmacology; D050901:Nitrate Reductase / Q000378:metabolism*; D009566:Nitrates; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D053723:Panax notoginseng / Q000187:drug effects / Q000201:enzymology* / Q000502:physiology; D010368:Pectins / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000201:enzymology* / Q000502:physiology; D010946:Plants, Medicinal; D011134:Polysaccharides / Q000378:metabolism; D017973:Tungsten Compounds / Q000494:pharmacology
chemical_list: D001565:Benzoates; D007093:Imidazoles; D009566:Nitrates; D020030:Nitric Oxide Donors; D010940:Plant Proteins; D011134:Polysaccharides; D017973:Tungsten Compounds; D002104:Cadmium; C079393:1,3-dihydroxy-4,4,5,5-tetramethyl-2-(4-carboxyphenyl)tetrahydroimidazole; D009599:Nitroprusside; D009569:Nitric Oxide; C007916:hemicellulose; D010368:Pectins; D050901:Nitrate Reductase; C045951:tungstate
keywords: Cd accumulation; Hemicellulose 1; Nitrate reductase; Nitric oxide; Panax notoginseng; Pectin