title: Excess copper induced physiological and proteomic changes in germinating rice seeds.
abstract: Copper is an essential micronutrient for plants. Present at a high concentration in soil, copper is also regarded as a major toxicant to plant cells due to its potential inhibitory effects against many physiological and biochemical processes. The interference of germination-related proteins by heavy metals has not been well documented at the proteomic level. In the current study, physiological, biochemical and proteomic changes of germinating rice seeds were investigated under copper stress. Germination rate, shoot elongation, plant biomass, and water content were decreased, whereas accumulation of copper and TBARS content in seeds were increased significantly with increasing copper concentrations from 0.2mM to 1.5mM followed by germination. The SDS-PAGE showed the preliminary changes in the polypeptides patterns under copper stress. Protein profiles analyzed by two-dimensional electrophoresis (2-DE) revealed that 25 protein spots were differentially expressed in copper-treated samples. Among them, 18 protein spots were up-regulated and 7 protein spots were down-regulated. These differentially displayed proteins were identified by MALDI-TOF mass spectrometry. The up-regulation of some antioxidant and stress-related proteins such as glyoxalase I, peroxiredoxin, aldose reductase, and some regulatory proteins such as DnaK-type molecular chaperone, UlpI protease, and receptor-like kinase clearly indicated that excess copper generates oxidative stress that might be disruptive to other important metabolic processes. Moreover, down-regulation of key metabolic enzymes like alpha-amylase or enolase revealed that the inhibition of seed germinations after exposure to excess copper not only affects starvation in water uptake by seeds but also results in failure in the reserve mobilization processes. These results indicate a good correlation between the physiological and biochemical changes in germinating rice seeds exposed to excess copper.
authors.affiliation: Department of Animal Science and Biotechnology, College of Agriculture and Life Sciences, Kyungpook National University, Daegu 702-701, Republic of Korea.
authors.forename: Nagib
authors.initials: N
authors.lastname: Ahsan
authors.forename: Dong-Gi
authors.initials: DG
authors.lastname: Lee
authors.forename: Sang-Hoon
authors.initials: SH
authors.lastname: Lee
authors.forename: Kyu Young
authors.initials: KY
authors.lastname: Kang
authors.forename: Jeung Joo
authors.initials: JJ
authors.lastname: Lee
authors.forename: Pil Joo
authors.initials: PJ
authors.lastname: Kim
authors.forename: Ho-Sung
authors.initials: HS
authors.lastname: Yoon
authors.forename: Jong-Sang
authors.initials: JS
authors.lastname: Kim
authors.forename: Byung-Hyun
authors.initials: BH
authors.lastname: Lee
mesh_terms: D018533:Biomass; D003300:Copper / Q000378:metabolism / Q000633:toxicity*; D018525:Germination / Q000187:drug effects / Q000502:physiology*; D012275:Oryza / Q000187:drug effects*; D018384:Oxidative Stress; D040901:Proteomics; D036226:Seedlings / Q000187:drug effects / Q000378:metabolism; D012639:Seeds / Q000187:drug effects / Q000254:growth & development*
chemical_list: D003300:Copper