Abstract
Auxin regulates a variety of physiological and developmental processes in plants. Although auxin acts as a suppressor of leaf senescence, its exact role in this respect has not been clearly defined, aside from circumstantial evidence. It was found here that ARF2 functions in the auxin-mediated control of Arabidopsis leaf longevity, as discovered by screening EMS mutant pools for a delayed leaf senescence phenotype. Two allelic mutations, ore14-1 and 14-2, caused a highly significant delay in all senescence parameters examined, including chlorophyll content, the photochemical efficiency of photosystem II, membrane ion leakage, and the expression of senescence-associated genes. A delay of senescence symptoms was also observed under various senescence-accelerating conditions, where detached leaves were treated with darkness, phytohormones, or oxidative stress. These results indicate that the gene defined by these mutations might be a key regulatory genetic component controlling functional leaf senescence. Map-based cloning of ORE14 revealed that it encodes ARF2, a member of the auxin response factor (ARF) protein family, which modulates early auxin-induced gene expression in plants. The ore14/arf2 mutation also conferred an increased sensitivity to exogenous auxin in hypocotyl growth inhibition, thereby demonstrating that ARF2 is a repressor of auxin signalling. Therefore, the ore14/arf2 lesion appears to cause reduced repression of auxin signalling with increased auxin sensitivity, leading to delayed senescence. Altogether, our data suggest that ARF2 positively regulates leaf senescence in Arabidopsis.
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Claims 5
Claim · model-written summary
The ore14-1 and 14-2 mutations significantly delayed leaf senescence parameters.
- Taxon
- Arabidopsis
Arabidopsise1 - Material
- ore14-1 and 14-2e0
- Treatment
- Two allelic mutations, ore14-1 and 14-2e0
- Outcome
- senescence parameterse0
- Direction
- delaye0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Two allelic mutations, ore14-1 and 14-2, caused a highly significant delay in all senescence parameters examined, including chlorophyll content, the photochemical efficiency of photosystem II, membrane ion leakage, and the expression of senescence-associated genes”
e1“Arabidopsis leaf longevity”
Claim · model-written summary
Mutant detached leaves showed delayed senescence symptoms under darkness, phytohormones, or oxidative stress.
- Taxon
- ArabidopsisArabidopsise1
- Organ / stage
- detached leavese0
- Treatment
- darkness, phytohormones, or oxidative stresse0
- Outcome
- senescence symptomse0
- Direction
- delaye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A delay of senescence symptoms was also observed under various senescence-accelerating conditions, where detached leaves were treated with darkness, phytohormones, or oxidative stress”
e1“Arabidopsis leaf longevity”
Claim · model-written summary
ORE14 was identified as encoding ARF2.
- Taxon
- ArabidopsisArabidopsise1
- Gene
- ORE14e0
- Outcome
- encodes ARF2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Map-based cloning of ORE14 revealed that it encodes ARF2”
e1“Arabidopsis leaf longevity”
Claim · model-written summary
The ore14/arf2 mutation increased sensitivity to exogenous auxin during hypocotyl growth inhibition.
- Taxon
- ArabidopsisArabidopsise1
- Organ / stage
- hypocotyle0
- Treatment
- ore14/arf2 mutatione0
- Outcome
- sensitivity to exogenous auxine0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The ore14/arf2 mutation also conferred an increased sensitivity to exogenous auxin in hypocotyl growth inhibition”
e1“Arabidopsis leaf longevity”
Claim · model-written summary
ARF2 was interpreted as a repressor of auxin signaling and positive regulator of leaf senescence.
- Taxon
- ArabidopsisArabidopsise1
- Gene
- ARF2e1
- Outcome
- leaf senescencee1
- Qualifier
- positively regulatese1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ARF2 is a repressor of auxin signalling”
e1“ARF2 positively regulates leaf senescence in Arabidopsis”
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