title: Hydrogen-rich water regulates cucumber adventitious root development in a heme oxygenase-1/carbon monoxide-dependent manner.
abstract: Hydrogen gas (H2) is an endogenous gaseous molecule in plants. Although its reputation is as a "biologically inert gas", recent results suggested that H2 has therapeutic antioxidant properties in animals and plays fundamental roles in plant responses to environmental stresses. However, whether H2 regulates root morphological patterns is largely unknown. In this report, hydrogen-rich water (HRW) was used to characterize H2 physiological roles and possible signaling transduction pathways in the promotion of adventitious root (AR) formation in cucumber explants. Our results showed that a 50% concentration of HRW was able to mimic the effect of hemin, an inducer of a carbon monoxide (CO) synthetic enzyme, and heme oxygenase-1 (HO-1), in restoring AR formation in comparison with the inhibition effect conferred by auxin-depletion treatment alone. It was further shown that the inducible effect of HRW could be further blocked by the co-treatment with N-1-naphthylphtalamic acid (NPA; an auxin transport inhibitor). The HRW-induced response, at least partially, was HO-1-dependent. This conclusion was supported by the fact that the exposure of cucumber explants to HRW up-regulates cucumber HO-1 gene expression and its protein levels. HRW-mediated induction of representative target genes related to auxin signaling and AR formation, such as CsDNAJ-1, CsCDPK1/5, CsCDC6, CsAUX22B-like, and CsAUX22D-like, and thereafter AR formation (particularly in the AR length) was differentially sensitive to the HO-1 inhibitor zinc protoporphyrin IX (ZnPP). Above blocking actions were clearly reversed by CO, further confirming that the above response was HO-1/CO-specific. However, the addition of a well-known antioxidant, ascorbic acid (AsA), failed to influence AR formation triggered by HRW, thus ruling out the involvement of redox homeostasis in this process. Together, these results indicated that HRW-induced adventitious rooting is, at least partially, correlated with the HO-1/CO-mediated responses. We also suggested that exogenous HRW treatment on plants might be a good option to induce root organogenesis.
authors: College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China.
authors: Yuting
authors: Y
authors: Lin
authors: College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China.
authors: Wei
authors: W
authors: Zhang
authors: College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China.
authors: Fang
authors: F
authors: Qi
authors: College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China.
authors: Weiti
authors: W
authors: Cui
authors: College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China.
authors: Yanjie
authors: Y
authors: Xie
authors: College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China. Electronic address: wbshenh@njau.edu.cn.
authors: Wenbiao
authors: W
authors: Shen
mesh_terms: D001205:Ascorbic Acid / Q000502:physiology; D002248:Carbon Monoxide / Q000378:metabolism*; D018553:Cucumis sativus / Q000254:growth & development*; D018506:Gene Expression Regulation, Plant; D051547:Heme Oxygenase-1 / Q000378:metabolism*; D006427:Hemin / Q000502:physiology; D006859:Hydrogen / Q000502:physiology*; D007210:Indoleacetic Acids / Q000378:metabolism; D010797:Phthalimides; D063245:Plant Development; D018517:Plant Roots / Q000254:growth & development*
chemical_list: D007210:Indoleacetic Acids; D010797:Phthalimides; C002687:alpha-naphthylphthalamic acid; C030737:indoleacetic acid; D006427:Hemin; D002248:Carbon Monoxide; D006859:Hydrogen; D051547:Heme Oxygenase-1; D001205:Ascorbic Acid
keywords: AR; Adventitious root formation; AsA; BR; Cucumber; Fe(2+); FeSO(4)·7H(2)O; H(2); H(2)O(2); H(2)S; HO-1/CO; HRW; Heme oxygenase-1/carbon monoxide; Hydrogen gas; Hydrogen-rich water; N-1-naphthylphthalamic acid; NO; NPA; ZnPP; adventitious roots; ascorbic acid; bilirubin; heme oxygenase-1/carbon monoxide; hydrogen gas; hydrogen peroxide; hydrogen sulfide; hydrogen-rich water; nitric oxide; zinc protoporphyrin IX