Abstract
The interactions between phytohormones are crucial for plants to adapt to complex environmental changes. One example is the ethylene-regulated local auxin biosynthesis in roots, which partly contributes to ethylene-directed root development and gravitropism. Using a chemical biology approach, we identified a small molecule, l-kynurenine (Kyn), which effectively inhibited ethylene responses in Arabidopsis thaliana root tissues. Kyn application repressed nuclear accumulation of the ETHYLENE INSENSITIVE3 (EIN3) transcription factor. Moreover, Kyn application decreased ethylene-induced auxin biosynthesis in roots, and TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS1/TRYPTOPHAN AMINOTRANSFERASE RELATEDs (TAA1/TARs), the key enzymes in the indole-3-pyruvic acid pathway of auxin biosynthesis, were identified as the molecular targets of Kyn. Further biochemical and phenotypic analyses revealed that Kyn, being an alternate substrate, competitively inhibits TAA1/TAR activity, and Kyn treatment mimicked the loss of TAA1/TAR functions. Molecular modeling and sequence alignments suggested that Kyn effectively and selectively binds to the substrate pocket of TAA1/TAR proteins but not those of other families of aminotransferases. To elucidate the destabilizing effect of Kyn on EIN3, we further found that auxin enhanced EIN3 nuclear accumulation in an EIN3 BINDING F-BOX PROTEIN1 (EBF1)/EBF2-dependent manner, suggesting the existence of a positive feedback loop between auxin biosynthesis and ethylene signaling. Thus, our study not only reveals a new level of interactions between ethylene and auxin pathways but also offers an efficient method to explore and exploit TAA1/TAR-dependent auxin biosynthesis.
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Claims 9
Claim · model-written summary
L-kynurenine inhibited ethylene responses in Arabidopsis root tissues.
- Taxon
- Arabidopsis thaliana
Arabidopsis thalianae0 - Organ / stage
- root tissuese0
- Treatment
- l-kynureninee0
- Outcome
- ethylene responsese0
- Direction
- inhibitede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“we identified a small molecule, l-kynurenine (Kyn), which effectively inhibited ethylene responses in Arabidopsis thaliana root tissues.”
Claim · model-written summary
Kyn application repressed nuclear accumulation of EIN3.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- Kyn applicatione0
- Gene
- ETHYLENE INSENSITIVE3 (EIN3)e0
- Outcome
- nuclear accumulation of the ETHYLENE INSENSITIVE3 (EIN3) transcription factore0
- Direction
- repressede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Kyn application repressed nuclear accumulation of the ETHYLENE INSENSITIVE3 (EIN3) transcription factor.”
t0“Arabidopsis”
Claim · model-written summary
Kyn application decreased ethylene-induced auxin biosynthesis in roots.
- Taxon
- ArabidopsisArabidopsist0
- Organ / stage
- rootse0
- Treatment
- Kyn applicatione0
- Outcome
- ethylene-induced auxin biosynthesise0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Kyn application decreased ethylene-induced auxin biosynthesis in roots, and TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS1/TRYPTOPHAN AMINOTRANSFERASE RELATEDs (TAA1/TARs), the key enzymes in the indole-3-pyruvic acid pathway of auxin biosynthesis, were identified as the molecular targets of Kyn.”
t0“Arabidopsis”
Claim · model-written summary
TAA1/TAR enzymes were identified as molecular targets of Kyn.
- Taxon
- ArabidopsisArabidopsist0
- Gene
- TAA1/TARse0
- Outcome
- molecular targets of Kyne0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Kyn application decreased ethylene-induced auxin biosynthesis in roots, and TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS1/TRYPTOPHAN AMINOTRANSFERASE RELATEDs (TAA1/TARs), the key enzymes in the indole-3-pyruvic acid pathway of auxin biosynthesis, were identified as the molecular targets of Kyn.”
t0“Arabidopsis”
Claim · model-written summary
Kyn competitively inhibited TAA1/TAR activity as an alternate substrate.
- Taxon
- ArabidopsisArabidopsist0
- Gene
- TAA1/TARe0
- Outcome
- TAA1/TAR activitye0
- Direction
- inhibitse0
- Qualifier
- alternate substratee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Further biochemical and phenotypic analyses revealed that Kyn, being an alternate substrate, competitively inhibits TAA1/TAR activity, and Kyn treatment mimicked the loss of TAA1/TAR functions.”
t0“Arabidopsis”
Claim · model-written summary
Kyn treatment mimicked loss of TAA1/TAR functions.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- Kyn treatmente0
- Gene
- TAA1/TARe0
- Outcome
- loss of TAA1/TAR functionse0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Further biochemical and phenotypic analyses revealed that Kyn, being an alternate substrate, competitively inhibits TAA1/TAR activity, and Kyn treatment mimicked the loss of TAA1/TAR functions.”
t0“Arabidopsis”
Claim · model-written summary
Modeling suggested selective Kyn binding to the TAA1/TAR substrate pocket compared with other aminotransferase families.
- Taxon
- ArabidopsisArabidopsist0
- Gene
- TAA1/TAR proteinse0
- Outcome
- binds to the substrate pocket of TAA1/TAR proteinse0
- Comparator
- other families of aminotransferasese0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Molecular modeling and sequence alignments suggested that Kyn effectively and selectively binds to the substrate pocket of TAA1/TAR proteins but not those of other families of aminotransferases.”
t0“Arabidopsis”
Claim · model-written summary
Auxin enhanced EIN3 nuclear accumulation in an EBF1/EBF2-dependent manner.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- auxine0
- Gene
- EIN3e0
- Outcome
- EIN3 nuclear accumulatione0
- Direction
- enhancede0
- Qualifier
- EBF2-dependent mannere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“auxin enhanced EIN3 nuclear accumulation in an EIN3 BINDING F-BOX PROTEIN1 (EBF1)/EBF2-dependent manner, suggesting the existence of a positive feedback loop between auxin biosynthesis and ethylene signaling.”
t0“Arabidopsis”
Claim · model-written summary
The authors suggest a positive feedback loop between auxin biosynthesis and ethylene signaling.
- Taxon
- ArabidopsisArabidopsist0
- Outcome
- positive feedback loop between auxin biosynthesis and ethylene signalinge0
- Qualifier
- positive feedback loope0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“auxin enhanced EIN3 nuclear accumulation in an EIN3 BINDING F-BOX PROTEIN1 (EBF1)/EBF2-dependent manner, suggesting the existence of a positive feedback loop between auxin biosynthesis and ethylene signaling.”
t0“Arabidopsis”
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class · physiology: hormones · ArabidopsisPositive and negative results
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