Abstract
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.
Highlights
The phytohormone 7-iso-(+)-jasmonoyl-L-isoleucine (JA-Ile) mediates plant defense responses against herbivore and pathogen attack, and increases plant resistance against foreign invaders
Analogs of 3 with partially altered shapes compared with the original molecule might exhibit selectivity for protein-protein interactions (PPIs) induction between CORONATINE INSENSITIVE1 (COI1) and some JASMONATE ZIM DOMAIN (JAZ) subtypes over others (Fig. 1b,c)
These results showed that the ketone oxygen of 3 mainly forms hydrogen bonds with the NH1-proton of R496 (COI1) and NH-proton of A204 (JAZ1) during the molecular dynamics (MD) simulation, indicating the importance of these hydrogen bonds for the binding of JAZ1 with COI1
Summary
The phytohormone 7-iso-(+)-jasmonoyl-L-isoleucine (JA-Ile) mediates plant defense responses against herbivore and pathogen attack, and increases plant resistance against foreign invaders. CORONATINE INSENSITIVE1 (COI1; the F-box subunit of the skp/Cullin/F-box-type ubiquitin ligase complex) and JASMONATE ZIM DOMAIN (JAZ) transcriptional repressor proteins[9,10,11], leading to plant defense responses, as well as plant growth inhibition or senescence[6,7]. Such a growth-defense trade off[12] is partly due to resource allocation in the plant body, as upregulating defense responses requires plant nutrients, thereby suppressing plant growth[8]. PPI induction between COI1 and specific JAZ subtypes is only involved in plant defense responses It might allow activation of plant defenses but do not cause growth inhibition. The detailed physiological functions of all JAZ subtypes remain unclear, as genetic analyses have sometimes provided enigmatic results due to the complexity of the JA-mediated signaling cascade—the genetic redundancy of JAZ genes, the involvement of multiple co-acting factors[15], and signaling crosstalk with other phytohormones[18,19,20,21] have all been observed; and a well-known antagonistic interaction occurs between JA-mediated defense responses against necrotrophs and salicylic acid (SA)mediated defense responses against biotrophs[21,22,23]
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