Abstract
A novel abscisic acid (ABA)-deficient mutant, aba4, was identified in a screen for paclobutrazol-resistant germination. Compared with wild-type, the mutant showed reduced endogenous ABA levels in both dehydrated rosettes and seeds. Carotenoid composition analysis demonstrated that the defective locus affects neoxanthin synthesis. The ABA4 gene was identified by map-based cloning, and found to be a unique gene in the Arabidopsis genome. The predicted protein has four putative helical transmembrane domains and shows significant similarity to predicted proteins from tomato, rice and cyanobacteria. Constitutive expression of the ABA4 gene in Arabidopsis transgenic plants led to increased accumulation of trans-neoxanthin, indicating that the ABA4 protein has a direct role in neoxanthin synthesis. aba4 mutant phenotypes were mild compared with previously identified ABA-deficient mutants that exhibit vegetative tissue phenotypes. Indeed, ABA levels in seeds of aba4 mutants were higher than those of aba1 mutants. As aba1 mutants are also affected in a unique gene, this suggests that ABA can be produced in the aba4 mutant by an alternative pathway using violaxanthin as a substrate. It appears, therefore, that in Arabidopsis both violaxanthin and neoxanthin are in vivo substrates for 9-cis-epoxycarotenoid dioxygenases. Furthermore, significantly reduced levels of ABA were synthesized in the aba4 mutant on dehydration, demonstrating that ABA biosynthesis in response to stress must occur mainly via neoxanthin isomer precursors.
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Claims 13
Claim · model-written summary
The aba4 mutant had reduced ABA in dehydrated rosettes and seeds.
- Taxon
- Arabidopsis
Arabidopsist0 - Material
- aba4t0
- Organ / stage
- dehydrated rosettes and seedse0
- Outcome
- endogenous ABA levelse0
- Direction
- reducede0
- Comparator
- wild-typee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Compared with wild-type, the mutant showed reduced endogenous ABA levels in both dehydrated rosettes and seeds.”
t0“The Arabidopsis ABA‐deficient mutant aba4”
Claim · model-written summary
The defective aba4 locus affects neoxanthin synthesis.
- Taxon
- ArabidopsisArabidopsist0
- Gene
- aba4t0
- Outcome
- neoxanthin synthesise0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the defective locus affects neoxanthin synthesis”
t0“The Arabidopsis ABA‐deficient mutant aba4”
Claim · model-written summary
ABA4 was identified as a unique gene in the Arabidopsis genome.
- Taxon
- ArabidopsisArabidopsise0
- Gene
- ABA4e0
- Outcome
- a unique gene in the Arabidopsis genomee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The ABA4 gene was identified by map-based cloning, and found to be a unique gene in the Arabidopsis genome.”
Claim · model-written summary
The predicted ABA4 protein has four putative transmembrane helices.
- Taxon
- ArabidopsisArabidopsist0
- Gene
- ABA4e1
- Outcome
- four putative helical transmembrane domainse0
- Value
- foure0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The predicted protein has four putative helical transmembrane domains”
e1“The ABA4 gene was identified”
t0“The Arabidopsis ABA‐deficient mutant aba4”
Claim · model-written summary
ABA4 protein shows similarity to predicted proteins from tomato, rice and cyanobacteria.
- Taxon
- ArabidopsisArabidopsist0
- Gene
- ABA4e1
- Outcome
- significant similarity to predicted proteins from tomato, rice and cyanobacteriae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“shows significant similarity to predicted proteins from tomato, rice and cyanobacteria”
e1“The ABA4 gene was identified”
t0“The Arabidopsis ABA‐deficient mutant aba4”
Claim · model-written summary
Constitutive ABA4 expression increased trans-neoxanthin accumulation.
- Taxon
- ArabidopsisArabidopsise0
- Treatment
- Constitutive expression of the ABA4 genee0
- Gene
- ABA4e0
- Outcome
- accumulation of trans-neoxanthine0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Constitutive expression of the ABA4 gene in Arabidopsis transgenic plants led to increased accumulation of trans-neoxanthin”
Claim · model-written summary
The authors infer ABA4 protein directly contributes to neoxanthin synthesis.
- Taxon
- ArabidopsisArabidopsist0
- Gene
- ABA4 proteine0
- Outcome
- neoxanthin synthesise0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the ABA4 protein has a direct role in neoxanthin synthesis”
t0“The Arabidopsis ABA‐deficient mutant aba4”
Claim · model-written summary
The aba4 phenotype was mild relative to earlier ABA-deficient mutants.
- Taxon
- ArabidopsisArabidopsist0
- Material
- aba4e0
- Outcome
- mutant phenotypese0
- Direction
- milde0
- Comparator
- previously identified ABA-deficient mutantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“aba4 mutant phenotypes were mild compared with previously identified ABA-deficient mutants that exhibit vegetative tissue phenotypes.”
t0“The Arabidopsis ABA‐deficient mutant aba4”
Claim · model-written summary
ABA in aba4 seeds exceeded that in aba1 seeds.
- Taxon
- ArabidopsisArabidopsist0
- Material
- aba4 mutantse0
- Outcome
- ABA levels in seedse0
- Direction
- highere0
- Comparator
- aba1 mutantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ABA levels in seeds of aba4 mutants were higher than those of aba1 mutants.”
t0“The Arabidopsis ABA‐deficient mutant aba4”
Claim · model-written summary
The authors suggest an alternative violaxanthin-dependent ABA pathway in aba4.
- Taxon
- ArabidopsisArabidopsist0
- Gene
- aba4e0
- Compound
- violaxanthine0
- Outcome
- ABA can be producede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ABA can be produced in the aba4 mutant by an alternative pathway using violaxanthin as a substrate”
t0“The Arabidopsis ABA‐deficient mutant aba4”
Claim · model-written summary
Violaxanthin and neoxanthin appear to be in vivo substrates for 9-cis-epoxycarotenoid dioxygenases.
- Taxon
- ArabidopsisArabidopsise0
- Gene
- 9-cis-epoxycarotenoid dioxygenasese0
- Outcome
- violaxanthin and neoxanthin are in vivo substratese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in Arabidopsis both violaxanthin and neoxanthin are in vivo substrates for 9-cis-epoxycarotenoid dioxygenases”
Claim · model-written summary
Dehydrated aba4 synthesized significantly less ABA.
- Taxon
- ArabidopsisArabidopsist0
- Material
- aba4 mutante0
- Treatment
- dehydratione0
- Outcome
- levels of ABAe0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“significantly reduced levels of ABA were synthesized in the aba4 mutant on dehydration”
t0“The Arabidopsis ABA‐deficient mutant aba4”
Claim · model-written summary
The authors infer stress-induced ABA biosynthesis occurs mainly through neoxanthin isomer precursors.
- Taxon
- ArabidopsisArabidopsist0
- Compound
- neoxanthin isomer precursorse0
- Outcome
- ABA biosynthesis in response to stresse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ABA biosynthesis in response to stress must occur mainly via neoxanthin isomer precursors”
t0“The Arabidopsis ABA‐deficient mutant aba4”
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See all 36 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.