The genuine ligand of a jasmonic acid receptor

Abstract

Jasmonic acid (JA), its metabolites, such as the methyl ester or amino acid conjugates as well as its precursor 12-oxophytodienoic acid (OPDA) are lipid-derived signals. JA, OPDA and JA-amino acid conjugates are known to function as signals in plant stress responses and development. More recently, formation of JA-amino acid conjugates and high biological activity of JA-Isoleucine (JA-Ile) were found to be essential in JA signalling. A breakthrough was the identification of JAZ proteins which interact with the F-box protein COI1 if JA-Ile is bound. This interaction leads to proteasomal degradation of JAZs being negative regulators of JA-induced transcription. Surprisingly, a distinct stereoisomer of JA-Ile, the (+)-7-iso-JA-Ile ((3R,7S) form) is most active. Coronatine, a bacterial phytotoxine with an identical stereochemistry at the cyclopentanone ring, has a similar bioactivity . This was explained by the recent identification of COI1 as the JA receptor and accords well with molecular modelling studies. Whereas over the last two decades JA was quantified to describe any JA dependent process, now we have to take into account a distinct stereoisomer of JA-Ile. Until recently a quantitative analysis of (+)-7-iso-JA-Ile was missing presumable due to its equilibration to (-)-JA-Ile. Now such an analysis was achieved. These aspects will be discussed based on our new knowledge on JA perception and signalling.

Acknowledgements

The authors' laboratory work was financially supported by a grant of the graduate program of the excellence cluster initiative of Sachsen-Anhalt, Germany (C.W.) and by the National Science Foundation of China, The National Basic Research 973 Program of China, and the Tsinghua-Yue-Yuen Medical Sciences Fund and grant from Chinese Academy of Sciences (D.X.). We thank B. Hause for critical reading of the manuscript.

Figures and Tables

Figure 1 Stuctures of (+)-7-iso-JA-L-ile [(3R,7S)-JA-L-ile], coronatine (COR), (−)-JA-L-Ile [(3R,7R)-JA-L-Ile] and (+)-JA-L-Ile [(3S,7S)-JA-L-Ile].

Figure 2 Coronatine and JA-Ile could fit within the surface pocket of COI1. Molecular modeling of the interaction between COI1 and Coronatine (A), (+)-7-iso-JA-Ile (B) or MeJA (C). Left panel: chemical structures of the jasmonates. Middle panel: the pose with the highest GoldScore fitness value in the molecular docking simulation. The jasmonates are shown as red sticks. The surface pocket of COI1 is shown in grey. Right panel: superposition of representative frames of the restricted molecular dynamics simulation. Frames at the early, intermediate and late stages were extracted and superimposed. The jasmonates are shown as pink sticks, and their interacting residues are shown as white lines. Polar contacts are shown as yellow dotted lines (modified from Yan et al., 200926).