A Small-Molecule Screen Identifies l-Kynurenine as a Competitive Inhibitor of TAA1/TAR Activity in Ethylene-Directed Auxin Biosynthesis and Root Growth in Arabidopsis

A Proposed Model Illustrating the Interaction between Ethylene Signaling and Auxin Biosynthesis in the Regulation of Root Elongation.Ethylene acts to stabilize EIN3 through its canonical signaling pathway, and the accumulated EIN3 transcription factor activates the expression of several auxin biosynthetic genes, including WEI2, WEI7, TAA1, and TAR2. WEI2 and WEI7 are required for Trp production, while TAA1 and TAR2 (and probably other TARs as well) convert Trp into IPyA, which eventually leads to the synthesis of IAA and the inhibition of root elongation. In addition to promoting ethylene biosynthesis, IAA is also able to enhance EIN3 stability probably by repressing EBF1/2-mediated EIN3 degradation, forming a positive feedback loop between ethylene signaling and auxin biosynthesis. Kyn has been identified in this study as a small compound that competitively and selectively inhibits the family of TAA1/TARs.[See online article for color version of this figure.]

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A Small-Molecule Screen Identifies l-Kynurenine as a Competitive Inhibitor of TAA1/TAR Activity in Ethylene-Directed Auxin Biosynthesis and Root Growth in Arabidopsis. (2011) Wenrong He, et al. Plant Cell. 2011 Nov;23(11):3944-3960. Figure: F9. Arabidopsis thaliana

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