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

Abstract

Despite 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 NH4 Cl up-regulated rice OsSE5 expression. Oxidative stress and subsequent growth inhibition induced by excess NH4 Cl 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 NH4 Cl-triggered reactive oxygen species overproduction, lipid peroxidation and growth inhibition. OsSE5 RNAi transgenic rice plants revealed NH4 Cl-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 NH4 Cl, 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.

l‐cysteine desulfhydrase‐related H2S production is involved in OsSE5‐promoted ammonium tolerance in roots of Oryza sativa

“…Regarding to antioxidant enzymes, activities of SOD, APX and CAT were detected. Upon NH 4 Cl exposure, the total activities of SOD, APX and CAT were reduced respectively, which showed a similar tendency as our previous results (Xie et al, ). Pretreatment of NaHS followed by NH 4 Cl treatment showed alleviation in the decreases of total activities of SOD, APX and CAT (Supporting Information Fig.…”

“…OsSE5 was also involved in the improvement of plant tolerance to NH 4 + stress in both NH 4 + ‐tolerant (rice) and NH 4 + ‐sensitive species (Arabidopsis) by the activation of antioxidant defence, thereby neutralizing excess reactive oxygen species produced by excess NH 4 + (Xie et al . ). Interestingly, up‐regulation of soybean HO could protect the soybean nodule nitrogen fixation and assimilation under salt stress (Zilli et al .…”

The Nrf2‐ARE pathway is associated with Schisandrin b attenuating benzo(a)pyrene‐Induced HTR cells damages in vitro

“…And SOD had been reported to resist BaP‐induced toxicity because of its anti‐oxidative stress property in rats and mice (Aktay et al, ; Sehgal et al, ). Although the direct defense of HO1 against BaP has not been studied, HO1 is well known for its anti‐oxidative, anti‐inflammatory and cytoprotective ability (Bhakkiyalakshmi et al, ; Xie et al, ). In addition, some studies had also reported that nuclear translocation of Nrf2 could activate the downstream HO1, NQO1, and SOD expression and therefore exert extensive cytoprotection including attenuating cell death, anti‐oxidative stress, anti‐tumor (Dinkova‐Kostova et al, ; Wang et al, ; Chao et al, ).…”

Haem oxygenase: A functionally diverse enzyme of photosynthetic organisms and its role in phytochrome chromophore biosynthesis, cellular signalling and defence mechanisms

“…Haem‐HO 1 is a novel antioxidant system, which results in the regulation of ammonium tolerance in rice HO 1 ( OsSE5 ). Results showed that OsSE5 RNAi transgenic rice plants exhibited enhanced tolerance to NH 4 Cl with an impaired antioxidant defence, which helps in improving plant tolerance to excess ammonium fertilizer (Xie et al, ). Recently, Santa‐Cruz et al () studied the mechanisms regulating HO 1 expression in soybean plants exposed to ultraviolet‐B (UV‐B) radiation that remains unexplored.…”