Enhanced tolerance to light stress of transgenic Arabidopsis plants that express the codA gene for a bacterial choline oxidase.
Arabidopsis thaliana was transformed with the codA gene from Arthrobacter globiformis. This gene encodes choline oxidase, an enzyme that converts choline to glycinebetaine. The photosynthetic activity, monitored in terms of chlorophyll fluorescence, of transformed plants was more tolerant to light stress than that of wild-type plants. This enhanced tolerance to light stress was caused by acceleration of the recovery of the photosystem II (PS II) complex from the photo-inactivated state. The transformed plants synthesized glycinebetaine, but no changes were detected in the relative levels of membrane lipids or in the relative levels of fatty acids in the various membrane lipids. Transformation with the codA gene increased levels of H2O2, a by-product of the reaction catalyzed by choline oxidase, by only 50% to 100% under stress or non-stress conditions. The activity of ascorbate peroxidase and, to a lesser extent, that of catalase in transformed plants were significantly higher than in the wild-type plants. These observations suggest that H2O2 produced by choline oxidase in the transformed plants might have stimulated the expression of H2O2 scavenging enzymes, with resultant maintenance of the level of H2O2 within a certain limited range. It appears that glycinebetaine produced in vivo, but not changes in membrane lipids or in the level of H2O2, protected the PS II complex in transformed plants from damage due to light stress.
Department of Regulation Biology, National Institute for Basic Biology, Okazaki, Japan.
Alia
Y
Y
Kondo
A
A
Sakamoto
H
H
Nonaka
H
H
Hayashi
P P
PP
Saradhi
T H
TH
Chen
N
N
Murata
D000222:Adaptation, Physiological / Q000235:genetics; D000429:Alcohol Oxidoreductases / Q000235:genetics* / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000502:physiology*; D001173:Arthrobacter / Q000201:enzymology; D060387:Ascorbate Peroxidases; D002374:Catalase / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D005227:Fatty Acids / Q000737:chemistry; D016166:Free Radical Scavengers / Q000378:metabolism; D015870:Gene Expression; D005798:Genes, Bacterial; D020404:Glycerophospholipids / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000378:metabolism; D008027:Light; D010544:Peroxidases / Q000378:metabolism; D010788:Photosynthesis / Q000528:radiation effects; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D030821:Plants, Genetically Modified; D012965:Sodium Chloride / Q000494:pharmacology; D013696:Temperature
D005227:Fatty Acids; D016166:Free Radical Scavengers; D020404:Glycerophospholipids; D012965:Sodium Chloride; D006861:Hydrogen Peroxide; D000429:Alcohol Oxidoreductases; C019888:choline oxidase; D010544:Peroxidases; D060387:Ascorbate Peroxidases; D002374:Catalase