Abstract
Physiological studies with excised stem segments have implicated the plant hormone indole-3-acetic acid (IAA or auxin) in the regulation of cell elongation. Supporting evidence from intact plants has been somewhat more difficult to obtain, however. Here, we report the identification and characterization of an auxin-mediated cell elongation growth response in Arabidopsis thaliana. When grown in the light at high temperature (29 degreesC), Arabidopsis seedlings exhibit dramatic hypocotyl elongation compared with seedlings grown at 20 degreesC. This temperature-dependent growth response is sharply reduced by mutations in the auxin response or transport pathways and in seedlings containing reduced levels of free IAA. In contrast, mutants deficient in gibberellin and abscisic acid biosynthesis or in ethylene response are unaffected. Furthermore, we detect a corresponding increase in the level of free IAA in seedlings grown at high temperature, suggesting that temperature regulates auxin synthesis or catabolism to mediate this growth response. Consistent with this possibility, high temperature also stimulates other auxin-mediated processes including auxin-inducible gene expression. Based on these results, we propose that growth at high temperature promotes an increase in auxin levels resulting in increased hypocotyl elongation. These results strongly support the contention that endogenous auxin promotes cell elongation in intact plants.
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Claims 7
Claim · model-written summary
At 29 degreesC, Arabidopsis hypocotyls elongated dramatically relative to 20 degreesC.
- Taxon
- Arabidopsis
Arabidopsise0 - Treatment
- high temperature (29 degreesC)e0
- Outcome
- hypocotyl elongatione0
- Direction
- dramatice0
- Comparator
- 20 degreesCe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When grown in the light at high temperature (29 degreesC), Arabidopsis seedlings exhibit dramatic hypocotyl elongation compared with seedlings grown at 20 degreesC.”
Claim · model-written summary
Auxin-response or transport mutations sharply reduced the temperature-dependent growth response.
- Taxon
- ArabidopsisArabidopsist0
- Outcome
- temperature-dependent growth responsee0
- Direction
- sharply reducede0
- Qualifier
- mutations in the auxin response or transport pathwayse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This temperature-dependent growth response is sharply reduced by mutations in the auxin response or transport pathways”
t0“Arabidopsis”
Claim · model-written summary
Reduced free IAA sharply reduced the temperature-dependent growth response.
- Taxon
- ArabidopsisArabidopsist0
- Outcome
- temperature-dependent growth responsee0
- Direction
- sharply reducede0
- Qualifier
- reduced levels of free IAAe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This temperature-dependent growth response is sharply reduced by mutations in the auxin response or transport pathways and in seedlings containing reduced levels of free IAA.”
t0“Arabidopsis”
Claim · model-written summary
Gibberellin-biosynthesis mutants were unaffected in the response.
- Taxon
- ArabidopsisArabidopsist0
- Outcome
- ethylene responsee0
- Direction
- unaffectede0
- Qualifier
- gibberellin and abscisic acid biosynthesise0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“mutants deficient in gibberellin and abscisic acid biosynthesis or in ethylene response are unaffected.”
t0“Arabidopsis”
Claim · model-written summary
High temperature raised free IAA in seedlings.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- high temperaturee0
- Outcome
- level of free IAAe0
- Direction
- increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“we detect a corresponding increase in the level of free IAA in seedlings grown at high temperature”
t0“Arabidopsis”
Claim · model-written summary
High temperature stimulated auxin-inducible gene expression.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- high temperaturee0
- Outcome
- auxin-inducible gene expressione0
- Direction
- stimulatese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“high temperature also stimulates other auxin-mediated processes including auxin-inducible gene expression.”
t0“Arabidopsis”
Claim · model-written summary
The authors propose that temperature increases auxin levels, causing more hypocotyl elongation.
- Taxon
- ArabidopsisArabidopsist0
- Outcome
- hypocotyl elongatione0
- Qualifier
- increase in auxin levelse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“growth at high temperature promotes an increase in auxin levels resulting in increased hypocotyl elongation.”
t0“Arabidopsis”
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