Plant biologists have been fascinated by auxin - a small chemical hormone so simple in structure yet so powerful - which regulates virtually every aspect of plant growth, development and behavior. Synthetic chemistry has played a major role in unraveling the physiological effects of auxin and the application of synthetic analogs has had a dramatic effect on tissue culture, horticulture and the agriculture of economically relevant plant species. Chemical genetics of the model plant Arabidopsis, has helped to elucidate the nuclear auxin signaling pathway mediated by the receptor, TIR1, and opened the door to structure-guided, rational designs of auxin agonists and antagonists. We have engineered an orthogonal auxin-TIR1 receptor pair, developed through a bump-and-hole strategy, that triggers auxin signaling without interfering with endogenous auxin or TIR1/AFBs. A synthetic, convex IAA (cvxIAA) hijacked the downstream auxin signaling in vivo both at the transcriptomic level and in specific developmental contexts, only in the presence of a complementary, concave TIR1 (ccvTIR1) receptor. Harnessing the cvxIAA-ccvTIR1 system,  we provide conclusive evidence for the role of the TIR1-mediated pathway in auxin-induced seedling acid growth, and further delve into the unprecedented, non-genomic rapid growth response mediated by auxin via TIR1. The cvxIAA-ccvTIR1 system serves as a powerful tool for solving outstanding questions in auxin biology and for precise manipulation of auxin-mediated processes as a controllable switch.

Harnessing synthetic chemistry to hijack auxin signaling in plants

2019 Spring National Meeting

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