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

Abstract

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 1 and K 1 both for germination and subsequent growth but were hypersensitive to Li 1 . 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 NaClinduced 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.

RETRACTED: HOS10 encodes an R2R3-type MYB transcription factor essential for cold acclimation in plants

“…The RT-PCR product was then subcloned into pGEM-T Easy Vector (Promega) and sequenced. The HOS10 was released from the resulting clone 10-133 and cloned into binary vector 99-1 between SacI and XbaI sites, resulting in an expression cassette of HOS10 under the control of the cauliflower mosaic virus 35 S promoter. The construct was introduced into hos10-1 mutant plants through an A. tumefaciens-mediated (strain GV3101) T-DNA transformation.…”

“…The HOS10 cDNA was cloned by RT-PCR using RNA prepared from wild-type plants. We conducted a complementation test by constitutive expression of HOS10 cDNA under the control of the cauliflower mosaic virus 35 S promoter. Twenty of 29 hos10-1 plants transformed with the wild-type HOS10 cDNA cassette exhibited wild-type phenotypes in the T 2 generation (Fig.…”

“…7G). HOS10 was fused in-frame to the C terminus of GFP and expressed under the control of the cauliflower mosaic virus 35 S promoter. We found that the GFP-HOS10 fusion protein accumulates in the nucleus with or without low-temperature treatment, consistent with its predicted function as a transcription factor (Fig.…”

High Temperature-Induced Abscisic Acid Biosynthesis and Its Role in the Inhibition of Gibberellin Action in Arabidopsis Seeds

“…It is also possible that the spatial distribution of carotenoid precursors and expression of ABA biosynthesis genes, including NCED itself, in a seed affect the contribution of each NCED to ABA biosynthesis. Among the five NCED genes in Arabidopsis, expression of NCED3 is induced by drought stress in plants (Iuchi et al, 2001;Ruggiero et al, 2004). In this study, we found that expression of NCED2, NCED5, and NCED9 was up-regulated by high temperature in after-ripened seeds under continuous illumination.…”

“…Each member of the NCED family plays a unique regulatory role in specific environmental responses and developmental processes. Expression of the NCED3 gene is induced by drought stress, and it plays a major role in ABA synthesis in response to the stress (Iuchi et al, 2001;Ruggiero et al, 2004). NCED6 expression is regulated in a photoreversible manner via phytochrome in seeds, and it plays a role in far-red light-induced suppression of seed germination .…”