Uncoupling the effects of abscisic acid on plant growth and water relations. Analysis of sto1/nced3, an abscisic acid-deficient but salt stress-tolerant mutant in Arabidopsis

• Published in: Plant physiology (Bethesda) 2004-10, Vol.136 (2), p.3134-3147
• Main Authors: Ruggiero, B, Koiwa, H, Manabe, Y, Quist, T.M, Inan, G, Saccardo, F, Joly, R.J, Hasegawa, P.M, Bressan, R.A, Maggio, A
• Format: Article
• Language: English
• Subjects: 9-cis-epoxicarotenoid dioxygenase; abscisic acid; Abscisic Acid - metabolism; Abscisic Acid - pharmacology; Abscisic Acid - physiology; Arabidopsis - drug effects; Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis thaliana; Biological and medical sciences; biosynthesis; chromosome mapping; circadian rhythm; Dehydration; Environmental Stress and Adaptation; ethylene; Ethylenes - pharmacology; Fundamental and applied biological sciences. Psychology; gene expression regulation; Genes; genetic complementation; Genetic mutation; Germination; hypersensitive response; insertional mutagenesis; Lithium Chloride - pharmacology; loci; messenger RNA; Molecular Sequence Data; mutants; Mutation; nucleotide sequences; Osmotic Pressure; osmotic stress; oxygenases; Phenotype; Phenotypes; phenotypic variation; Physical agents; Plant cells; Plant growth; Plant Leaves - metabolism; plant morphology; Plant physiology and development; plant proteins; plant stress; Plant Transpiration - genetics; plant-water relations; Plants; Potassium Chloride - pharmacology; Salt tolerance; Seedlings; signal transduction; Sodium Chloride - pharmacology; soil water; soil-plant interactions; stomatal movement; transfer DNA; transgenic plants; Vegetative apparatus, growth and morphogenesis. Senescence; Water - metabolism; water stress
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.104.046169

We have identified a T-DNA insertion mutation of Arabidopsis (ecotype C24), named sto1 (salt tolerant), that results in enhanced germination on both ionic (NaCl) and nonionic (sorbitol) hyperosmotic media. sto1 plants were more tolerant in vitro than wild type to Na(+) and K(+) both for germination and subsequent growth but were hypersensitive to Li(+). Postgermination growth of the sto1 plants on sorbitol was not improved. Analysis of the amino acid sequence revealed that STO1 encodes a 9-cis-epoxicarotenoid dioxygenase (similar to 9-cis-epoxicarotenoid dioxygenase GB:AAF26356 Phaseolus vulgaris and to NCED3 GB:AB020817 Arabidopsis), a key enzyme in the abscisic acid (ABA) biosynthetic pathway. STO1 transcript abundance was substantially reduced in mutant plants. Mutant sto1 plants were unable to accumulate ABA following a hyperosmotic stress, although their basal ABA level was only moderately altered. Either complementation of the sto1 with the native gene from the wild-type genome or supplementation of ABA to the growth medium restored the wild-type phenotype. Improved growth of sto1 mutant plants on NaCl, but not sorbitol, medium was associated with a reduction in both NaCl-induced expression of the ICK1 gene and ethylene accumulation. Osmotic adjustment of sto1 plants was substantially reduced compared to wild-type plants under conditions where sto1 plants grew faster. The sto1 mutation has revealed that reduced ABA can lead to more rapid growth during hyperionic stress by a signal pathway that apparently is at least partially independent of signals that mediate nonionic osmotic responses.