The phytohormone 7-iso-(+)-jasmonoyl-L-isoleucine (JA-Ile) mediates plant defense responses against herbivore and pathogen attack, and thus increases plant resistance against foreign invaders. However, JA-Ile also causes growth inhibition; and therefore JA-Ile is not a practical chemical regulator of plant defense responses. Here, we describe the rational design and synthesis of a small molecule agonist that can upregulate defense-related gene expression and promote pathogen resistance at concentrations that do not cause growth inhibition in Arabidopsis. By stabilizing interactions between COI1 and JAZ9 and JAZ10 but no other JAZ isoforms, the agonist leads to formation of JA-Ile co-receptors that selectively activate the JAZ9-EIN3/EIL1-ORA59 signaling pathway. The design of a JA-Ile agonist with high selectivity for specific protein subtypes may help promote the development of chemical regulators that do not cause a tradeoff between growth and defense.
Plant root systems are indispensable for water uptake, nutrient acquisition, and anchoring plants in the soil. Previous studies using auxin inhibitors definitively established that auxin plays a central role regulating root growth and development. Most auxin inhibitors affect all auxin signaling at the same time, which obscures an understanding of individual events. Here, we report that jasmonic acid (JA) functions as a lateral root (LR)-preferential auxin inhibitor in Arabidopsis () in a manner that is independent of the JA receptor, CORONATINE INSENSITIVE1 (COI1). Treatment of wild-type Arabidopsis with either (-)-JA or (+)-JA reduced primary root length and LR number; the reduction of LR number was also observed in mutants. Treatment of seedlings with (-)-JA or (+)-JA suppressed auxin-inducible genes related to LR formation, diminished accumulation of the auxin reporter, and inhibited auxin-dependent DII-VENUS degradation. A structural mimic of (-)-JA and (+)-coronafacic acid also inhibited LR formation and stabilized DII-VENUS protein. COI1-independent activity was retained in the double mutant of and () but reduced in the single mutant. These results reveal JAs and (+)-coronafacic acid to be selective counter-auxins, a finding that could lead to new approaches for studying the mechanisms of LR formation.
γ-Linolenic acid (GLA) is reported to show tumor-selective cytotoxicity via unidentified mechanisms. We introduced deuterium into GLA as a dual functional tag for metabolic inhibition and Raman imaging and applied for mechanistic studies.
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