title: Plant growth enhancement and associated physiological responses are coregulated by ethylene and gibberellin in response to harpin protein Hpa1.
abstract: The harpin protein Hpa1 produced by the bacterial blight pathogen of rice induces several growth-promoting responses in plants, activating the ethylene signaling pathway, increasing photosynthesis rates and EXPANSIN (EXP) gene expression levels, and thereby enhancing the vegetative growth. This study was attempted to analyze any mechanistic connections among the above and the role of gibberellin in these responses. Hpa1-induced growth enhancement was evaluated in Arabidopsis, tomato, and rice. And growth-promoting responses were determined mainly as an increase of chlorophyll a/b ratio, which indicates a potential elevation of photosynthesis rates, and enhancements of photosynthesis and EXP expression in the three plant species. In Arabidopsis, Hpa1-induced growth-promoting responses were partially compromised by a defect in ethylene perception or gibberellin biosynthesis. In tomato and rice, compromises of Hpa1-induced growth-promoting responses were caused by a pharmacological treatment with an ethylene perception inhibitor or a gibberellin biosynthesis inhibitor. In the three plant species, moreover, Hpa1-induced growth-promoting responses were significantly impaired, but not totally eliminated, by abolishing ethylene perception or gibberellin synthesis. However, simultaneous nullifications in both ethylene perception and gibberellin biosynthesis almost canceled the full effects of Hpa1 on plant growth, photosynthesis, and EXP2 expression. Theses results suggest that ethylene and gibberellin coregulate Hpa1-induced plant growth enhancement and associated physiological and molecular responses.
authors.affiliation: State Ministry of Education Key Laboratory of Integrated Management of Crop Pathogens and Insect Pests, Nanjing Agricultural University, Nanjing, 210095, China.
authors.forename: Xiaojie
authors.initials: X
authors.lastname: Li
authors.forename: Bing
authors.initials: B
authors.lastname: Han
authors.forename: Manyu
authors.initials: M
authors.lastname: Xu
authors.forename: Liping
authors.initials: L
authors.lastname: Han
authors.forename: Yanying
authors.initials: Y
authors.lastname: Zhao
authors.forename: Zhilan
authors.initials: Z
authors.lastname: Liu
authors.forename: Hansong
authors.initials: H
authors.lastname: Dong
authors.forename: Chunling
authors.initials: C
authors.lastname: Zhang
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D001425:Bacterial Outer Membrane Proteins / Q000494:pharmacology*; D002734:Chlorophyll / Q000378:metabolism; D005030:Ethylenes / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005875:Gibberellins / Q000378:metabolism; D018551:Solanum lycopersicum / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D009154:Mutation; D012275:Oryza / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D010788:Photosynthesis; D010937:Plant Growth Regulators / Q000378:metabolism*; D018515:Plant Leaves / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D036226:Seedlings / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects*
chemical_list: D001425:Bacterial Outer Membrane Proteins; D005030:Ethylenes; D005875:Gibberellins; D010937:Plant Growth Regulators; D010940:Plant Proteins; C095825:expansin protein, plant; D002734:Chlorophyll; C087295:HrpZ protein, Pseudomonas syringae; C036216:ethylene