title: Hydrogen peroxide-mediated growth of the root system occurs via auxin signaling modification and variations in the expression of cell-cycle genes in rice seedlings exposed to cadmium stress.
abstract: The link between root growth, H₂O₂, auxin signaling, and the cell cycle in cadmium (Cd)-stressed rice (Oryza sativa L. cv. Zhonghua No. 11) was analyzed in this study. Exposure to Cd induced a significant accumulation of Cd, but caused a decrease in zinc (Zn) content which resulted from the decreased expression of OsHMA9 and OsZIP. Analysis using a Cd-specific probe showed that Cd was mainly localized in the meristematic zone and vascular tissues. Formation and elongation of the root system were significantly promoted by 3-amino-1,2,4-triazole (AT), but were markedly inhibited by N,N'-dimethylthiourea (DMTU) under Cd stress. The effect of H₂O₂ on Cd-stressed root growth was further confirmed by examining a gain-of-function rice mutant (carrying catalase1 and glutathione-S-transferase) in the presence or absence of diphenylene iodonium. DR5-GUS staining revealed close associations between H₂O₂ and the concentration and distribution of auxin. H₂O₂ affected the expression of key genes, including OsYUCCA, OsPIN, OsARF, and OsIAA, in the auxin signaling pathway in Cd-treated plants. These results suggest that H₂O₂ functions upstream of the auxin signaling pathway. Furthermore, H₂O₂ modified the expression of cell-cycle genes in Cd-treated roots. The effects of H₂O₂ on root system growth are therefore linked to auxin signal modification and to variations in the expression of cell-cycle genes in Cd-stressed rice. A working model for the effects of H₂O₂ on Cd-stressed root system growth is thus proposed and discussed in this paper.
authors.affiliation: College of Life Sciences, Shandong University of Technology, Zibo 255049, China. zhaofengyun@sdut.edu.cn
authors.forename: Feng-Yun
authors.initials: FY
authors.lastname: Zhao
authors.forename: Ming-Ming
authors.initials: MM
authors.lastname: Han
authors.forename: Shi-Yong
authors.initials: SY
authors.lastname: Zhang
authors.forename: Kai
authors.initials: K
authors.lastname: Wang
authors.forename: Cheng-Ren
authors.initials: CR
authors.lastname: Zhang
authors.forename: Tao
authors.initials: T
authors.lastname: Liu
authors.forename: Wen
authors.initials: W
authors.lastname: Liu
mesh_terms: D002104:Cadmium / Q000633:toxicity*; D018816:Genes, cdc; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D007210:Indoleacetic Acids / Q000378:metabolism*; D012275:Oryza / Q000166:cytology / Q000235:genetics*; D018517:Plant Roots / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*
chemical_list: D007210:Indoleacetic Acids; D002104:Cadmium; D006861:Hydrogen Peroxide