title: Protective role of hydrogen peroxide pretreatment on defense systems and BnMP1 gene expression in Cr(VI)-stressed canola seedlings.
abstract: To evaluate the ameliorating effects of hydrogen peroxide (H2O2, 200 μM) on hexavalent chromium [Cr(VI)] toxicity in canola (Brassica napus L.), we focused on the plant growth, chlorophyll content, thiol contents, lipid peroxidation, antioxidant enzymes, and the expression of metallothionein protein (BnMP1) mRNA. Cr(VI) at 50 μM significantly decreased the plant growth (fresh and dry weights). The decrease in growth was accompanied by increased lipid peroxidation and decreased chlorophyll content in leaves. Hydrogen peroxide pretreatment, however, enhanced plant growth parameters and led to the reduced levels of lipid peroxidation and higher levels of pigment. In addition, H2O2 pretreatment increased Cr accumulation in aerial parts of seedlings. The tendency of increase in thiol content under Cr(VI) stress was further increased with H2O2 pretreatment. The activities of antioxidant enzymes such as superoxide dismutase (SOD), ascorbate peroxidase (APX), guaiacol peroxidase (POD) and catalase (CAT) were differentially altered. SOD and POD activities increased under Cr(VI) stress, whereas APX and CAT activities decreased. The SOD and CAT activities remained unaffected in both durations due to H2O2 pretreatment, but activities of APX and POD were promoted in the Cr(VI)-stressed seedlings. Metallothioneins are a family of low-molecular-weight Cys-rich proteins and are thought to play a possible role in metal metabolism or detoxification. In real-time quantitative PCR analysis, the expression level of BnMP1 mRNA was increased at 1 day after treatment (DAT), whereas it was decreased at 7 DAT in Cr(VI)-stressed seedlings. At 1 DAT, pretreatment of H2O2 before Cr(VI) stress reduced the expression of BnMP1 mRNA as compared to Cr(VI) stress alone, but this effect was not significant. At 7 DAT, H2O2 pretreatment alleviated the Cr(VI) stress-mediated decrease in the expression of BnMP1 mRNA. These results suggest that H2O2 may act as a signal that triggers defense mechanisms which in turn protects canola seedlings from Cr(VI)-induced oxidative damage.
authors: Department of Biology, Faculty of Science and Literature, Afyon Kocatepe University, 03030, Afyon, Turkey, mustafa_yildizus@yahoo.com.
authors: Mustafa
authors: M
authors: Yıldız
authors: Hakan
authors: H
authors: Terzi
authors: Nagihan
authors: N
authors: Bingül
mesh_terms: D000975:Antioxidants / Q000378:metabolism; D060387:Ascorbate Peroxidases / Q000378:metabolism; D029741:Brassica rapa / Q000737:chemistry / Q000187:drug effects* / Q000235:genetics; D002374:Catalase / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D002857:Chromium / Q000633:toxicity*; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D015227:Lipid Peroxidation / Q000187:drug effects; D008315:Malondialdehyde / Q000378:metabolism; D008668:Metallothionein / Q000235:genetics / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects; D009195:Peroxidase / Q000378:metabolism; D018515:Plant Leaves / Q000737:chemistry; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D036226:Seedlings / Q000187:drug effects* / Q000235:genetics; D013438:Sulfhydryl Compounds / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism
chemical_list: D000975:Antioxidants; D012333:RNA, Messenger; D013438:Sulfhydryl Compounds; D002857:Chromium; D002734:Chlorophyll; C074702:chromium hexavalent ion; D008315:Malondialdehyde; D008668:Metallothionein; D006861:Hydrogen Peroxide; C121048:guaiacol peroxidase; D060387:Ascorbate Peroxidases; D002374:Catalase; D009195:Peroxidase; D013482:Superoxide Dismutase
references: Ecotoxicology. 2012 Aug;21(6):1633-41
references: 22711547
references: Acta Biochim Biophys Sin (Shanghai). 2010 Feb;42(2):154-64
references: 20119627
references: Sci Total Environ. 2003 Jan 1;301(1-3):251-61
references: 12493201
references: Trends Plant Sci. 2002 Sep;7(9):405-10
references: 12234732
references: Protoplasma. 2012 Jul;249(3):599-611
references: 22002742
references: Plant Sci. 2001 Jan 5;160(2):291-299
references: 11164601
references: J Exp Bot. 2003 Oct;54(391):2285-92
references: 12947053
references: Plant Biol (Stuttg). 2011 Mar;13(2):225-32
references: 21309968
references: Ecotoxicology. 2012 Jul;21(5):1476-83
references: 22526926
references: Methods. 2001 Dec;25(4):402-8
references: 11846609
references: Ann Bot. 2009 Apr;103(6):923-30
references: 19201764
references: Plant Physiol. 2000 Jul;123(3):825-32
references: 10889232
references: Plant Physiol. 1993 Dec;103(4):1305-1309
references: 12232023
references: Anal Biochem. 1971 Nov;44(1):276-87
references: 4943714
references: Plant Cell. 1994 Jan;6(1):65-74
references: 12244221
references: Chemosphere. 2003 Dec;53(9):1147-53
references: 14512119
references: Arch Biochem Biophys. 1968 Apr;125(1):189-98
references: 5655425
references: J Plant Physiol. 2009 Sep 1;166(13):1446-52
references: 19375817
references: Chemosphere. 2000 Oct;41(7):1075-82
references: 10879826
references: Environ Pollut. 2008 Mar;152(1):32-40
references: 17644228
references: Annu Rev Plant Physiol Plant Mol Biol. 1998 Jun;49:249-279
references: 15012235
references: Methods Enzymol. 1984;105:121-6
references: 6727660
references: Annu Rev Plant Biol. 2002;53:159-82
references: 12221971
references: Environ Int. 2005 Jul;31(5):739-53
references: 15878200