Heme‐heme oxygenase 1 system is involved in ammonium tolerance by regulating antioxidant defence in Oryza sativa

• DOI: 10.1111/pce.12380
• Publication Date: 2014-06-06T11:53:06Z
• Authors: YANJIE XIE; YU MAO; SHENG XU; HENG ZHOU; XINGLIANG DUAN; WEITI CUI; JING ZHANG; GUOHUA XU
• Keywords: 2. Zero hunger; Carbon Monoxide; 0303 health sciences; Arabidopsis; Down-Regulation; Oryza; Plants, Genetically Modified; Plant Roots; 6. Clean water; Antioxidants; Up-Regulation; Oxidative Stress; 03 medical and health sciences; Gene Expression Regulation, Plant; Seedlings; Ammonium Compounds; Hemin; Lipid Peroxidation; Reactive Oxygen Species; Heme Oxygenase-1

AbstractDespite substantial evidence showing the ammonium‐altered redox homeostasis in plants, the involvement and molecular mechanism of heme‐heme oxygenase 1 (heme‐HO1), a novel antioxidant system, in the regulation of ammonium tolerance remain elusive. To fill in these gaps, the biological function of rice HO1 (OsSE5) was investigated. Results showed that NH4Cl up‐regulated rice OsSE5 expression. Oxidative stress and subsequent growth inhibition induced by excess NH4Cl was partly mitigated by pretreatment with carbon monoxide (CO, a by‐product of HO1 activity) or intensified by zinc protoporphyrin (ZnPP, a potent inhibitor of HO1 activity). Pretreatment with HO1 inducer hemin, not only up‐regulated OsSE5 expression and HO activity, but also rescued the down‐regulation of antioxidant transcripts, total and related isozymatic activities, thus significantly counteracting the excess NH4Cl‐triggered reactive oxygen species overproduction, lipid peroxidation and growth inhibition. OsSE5 RNAi transgenic rice plants revealed NH4Cl‐hypersensitive phenotype with impaired antioxidant defence, both of which could be rescued by CO but not hemin. Transgenic Arabidopsis plants over‐expressing OsSE5 also exhibited enhanced tolerance to NH4Cl, which might be attributed to the up‐regulation of several antioxidant transcripts. Altogether, these results illustrated the involvement of heme‐HO1 system in ammonium tolerance by enhancing antioxidant defence, which may improve plant tolerance to excess ammonium fertilizer.