title: Glycinebetaine accumulation is more effective in chloroplasts than in the cytosol for protecting transgenic tomato plants against abiotic stress.
abstract: Tomato (Lycopersicon esculentum Mill. cv. Moneymaker) plants were transformed with a gene for choline oxidase (codA) from Arthrobacter globiformis. The gene product (CODA) was targeted to the chloroplasts (Chl-codA), cytosol (Cyt-codA) or both compartments simultaneously (ChlCyt-codA). These three transgenic plant types accumulated different amounts and proportions of glycinebetaine (GB) in their chloroplasts and cytosol. Targeting CODA to either the cytosol or both compartments simultaneously increased total GB content by five- to sixfold over that measured from the chloroplast targeted lines. Accumulation of GB in codA transgenic plants was tissue dependent, with the highest levels being recorded in reproductive organs. Despite accumulating, the lowest amounts of GB, Chl-codA plants exhibited equal or higher degrees of enhanced tolerance to various abiotic stresses. This suggests that chloroplastic GB is more effective than cytosolic GB in protecting plant cells against chilling, high salt and oxidative stresses. Chloroplastic GB levels were positively correlated with the degree of oxidative stress tolerance conferred, whereas cytosolic GB showed no such a correlation. Thus, an increase in total GB content does not necessarily lead to enhanced stress tolerance, but additional accumulation of chloroplastic GB is likely to further raise the level of stress tolerance beyond what we have observed.
authors.affiliation: Department of Horticulture, ALS 4017, Oregon State University, Corvallis, OR 97331, USA.
authors.forename: Eung-Jun
authors.initials: EJ
authors.lastname: Park
authors.forename: Zoran
authors.initials: Z
authors.lastname: Jeknić
authors.forename: María-Teresa
authors.initials: MT
authors.lastname: Pino
authors.forename: Norio
authors.initials: N
authors.lastname: Murata
authors.forename: Tony Hwei-Hwang
authors.initials: TH
authors.lastname: Chen
mesh_terms: D000429:Alcohol Oxidoreductases / Q000235:genetics / Q000378:metabolism; D001173:Arthrobacter / Q000201:enzymology / Q000235:genetics; D001622:Betaine / Q000378:metabolism*; D002374:Catalase / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism*; D003080:Cold Temperature; D003600:Cytosol / Q000378:metabolism*; D018525:Germination / Q000502:physiology; D006861:Hydrogen Peroxide / Q000378:metabolism; D018551:Solanum lycopersicum / Q000235:genetics*; D018384:Oxidative Stress; D045332:Photosystem II Protein Complex / Q000502:physiology; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000254:growth & development / Q000378:metabolism* / Q000502:physiology; D021381:Protein Transport; D012965:Sodium Chloride / Q000378:metabolism
chemical_list: D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D001622:Betaine; D012965:Sodium Chloride; D006861:Hydrogen Peroxide; D000429:Alcohol Oxidoreductases; C019888:choline oxidase; D002374:Catalase