title: Ectopic expression of the cotton non-symbiotic hemoglobin gene GhHbd1 triggers defense responses and increases disease tolerance in Arabidopsis.
abstract: Plant non-symbiotic hemoglobins (nsHbs) play important roles in a variety of cellular processes. Previous evidence from this laboratory indicates that the expression of a class 1 nsHb gene (GhHb1) from cotton is induced in cotton roots challenged with the Verticillium wilt fungus. The present study examined further the expression patterns of the GhHb1 gene in cotton plants and characterized its in vivo function through ectopic overexpression of the gene in Arabidopsis thaliana. Expression of GhHb1 in cotton plants was induced by exogenously applied salicylic acid, methyl jasmonic acid, ethylene, hydrogen peroxide (H(2)O(2)) and nitric oxide (NO). Ectopic overproduction of GhHb1 in Arabidopsis led to constitutive expression of the defense genes PR-1 and PDF1.2, and conferred enhanced disease resistance to Pseudomonas syringae and tolerance to V. dahliae. GhHb1-transgenic Arabidopsis seedlings were more tolerant to exogenous NO and contained lower levels of cellular NO than the wild-type control. Moreover, transgenic plants with relatively high levels of expression of the GhHb1 gene developed spontaneous hypersensitive lesions on the leaves in the absence of pathogen inoculation. Our results indicate that GhHb1 proteins play a role in the defense responses against pathogen invasions, possibly by modulating the NO level and the ratio of H(2)O(2)/NO in the defense process.
authors.affiliation: State Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100080, PR China.
authors.forename: Zhan-Liang
authors.initials: ZL
authors.lastname: Qu
authors.forename: Nai-Qin
authors.initials: NQ
authors.lastname: Zhong
authors.forename: Hai-Yun
authors.initials: HY
authors.lastname: Wang
authors.forename: An-Ping
authors.initials: AP
authors.lastname: Chen
authors.forename: Gui-Liang
authors.initials: GL
authors.lastname: Jian
authors.forename: Gui-Xian
authors.initials: GX
authors.lastname: Xia
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000378:metabolism; D016923:Cell Death / Q000502:physiology; D023082:Defensins / Q000378:metabolism; D003368:Gossypium / Q000235:genetics; D006454:Hemoglobins / Q000235:genetics / Q000502:physiology*; D007113:Immunity, Innate / Q000235:genetics / Q000502:physiology*; D009569:Nitric Oxide / Q000378:metabolism*; D009599:Nitroprusside / Q000494:pharmacology; D030821:Plants, Genetically Modified; D044224:Pseudomonas syringae / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D020172:Verticillium / Q000472:pathogenicity / Q000502:physiology; D014774:Virulence
chemical_list: D029681:Arabidopsis Proteins; D023082:Defensins; D006454:Hemoglobins; D009569:Nitric Oxide; D009599:Nitroprusside; C487542:At5g44420 protein, Arabidopsis; C077262:PR-1 protein, Arabidopsis