title: Cadmium Disrupts the Balance between Hydrogen Peroxide and Superoxide Radical by Regulating Endogenous Hydrogen Sulfide in the Root Tip ofBrassica rapa.
abstract: Cd (cadmium) stress always alters the homeostasis of ROS (reactive oxygen species) including H2O2(hydrogen sulfide) and [Formula: see text] (superoxide radical), leading to the oxidative injury and growth inhibition in plants. In addition to triggering oxidative injury, ROS has been suggested as important regulators modulating root elongation. However, whether and how Cd stress induces the inhibition of root elongation by differentially regulating endogenous H2O2and [Formula: see text], rather than by inducing oxidative injury, remains elusive. To address these gaps, histochemical, physiological, and biochemical approaches were applied to investigate the mechanism for Cd to fine-tune the balance between H2O2and [Formula: see text] in the root tip ofBrassica rapa. Treatment with Cd at 4 and 16 μM significantly inhibited root elongation, while only 16 μM but not 4 μM of Cd induced oxidative injury and cell death in root tip. Fluorescent and pharmaceutical tests suggested that H2O2and [Formula: see text] played negative and positive roles, respectively, in the regulation of root elongation in the presence of Cd (4 μM) or not. Treatment with Cd at 4 μM led to the increase in H2O2and the decrease in [Formula: see text] in root tip, which may be attributed to the up-regulation ofBr_UPB1sand the down-regulation of their predicted targets (four peroxidase genes). Cd at 4 μM resulted in the increase in endogenous H2S in root tip by inducing the up-regulation ofLCDsandDCDs. Treatment with H2S biosynthesis inhibitor or H2S scavenger significantly blocked Cd (4 μM)-induced increase in endogenous H2S level, coinciding with the recovery of root elongation, the altered balance between H2O2and [Formula: see text], and the expression ofBr_UPB1sand two peroxidase genes. Taken together, it can be proposed that endogenous H2S mediated the phytotoxicity of Cd at low concentration by regulatingBr_UPB1s-modulated balance between H2O2and [Formula: see text] in root tip. Such findings shed new light on the regulatory role of endogenous H2S in plant adaptions to Cd stress.
authors.affiliation: Institute of Food Quality and Safety, Jiangsu Academy of Agricultural SciencesNanjing, China; College of Horticulture, Nanjing Agricultural UniversityNanjing, China; Key Lab of Food Quality and Safety of Jiangsu Province - State Key Laboratory Breeding Base, Jiangsu Provincial Department of Agriculture and ForestryNanjing, China.
authors.forename: Wenjing
authors.initials: W
authors.lastname: Lv
authors.affiliation: College of Horticulture, Nanjing Agricultural University Nanjing, China.
authors.forename: Lifei
authors.initials: L
authors.lastname: Yang
authors.affiliation: Central Laboratory, Jiangsu Academy of Agricultural Science Nanjing, China.
authors.forename: Cunfa
authors.initials: C
authors.lastname: Xu
authors.affiliation: Institute of Food Quality and Safety, Jiangsu Academy of Agricultural SciencesNanjing, China; Key Lab of Food Quality and Safety of Jiangsu Province - State Key Laboratory Breeding Base, Jiangsu Provincial Department of Agriculture and ForestryNanjing, China.
authors.forename: Zhiqi
authors.initials: Z
authors.lastname: Shi
authors.affiliation: Agricultural Products Quality and Safety Superivision, Inspection, and Testing Center, Ministry of Agriculture Nanjing, China.
authors.forename: Jinsong
authors.initials: J
authors.lastname: Shao
authors.affiliation: Department of Chemistry, Washington State University, Pullman WA, USA.
authors.forename: Ming
authors.initials: M
authors.lastname: Xian
authors.affiliation: Institute of Food Quality and Safety, Jiangsu Academy of Agricultural SciencesNanjing, China; Key Lab of Food Quality and Safety of Jiangsu Province - State Key Laboratory Breeding Base, Jiangsu Provincial Department of Agriculture and ForestryNanjing, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Chen
keywords: Brassica rapa; cadmium; hydrogen peroxide; hydrogen sulfide; root tip; superoxide radical