A tomato enzyme synthesizes (+)-7-iso-jasmonoyl-l-isoleucine in wounded leaves

Abstract

Jasmonoyl-L-isoleucine (JA-Ile) is a key jasmonate signal that probably functions in all plant species. The JASMONATE RESISTANT 1 (JAR1) enzyme synthesizes JA-Ile in Arabidopsis [Arabidopsis thaliana (L.) Heynh.], but a similar enzyme from tomato [Solanum lycopersicum (L.)] was not previously described. Tomato SlJAR1 has 66% sequence identity with Arabidopsis JAR1 and the SlJAR1-GST fusion protein purified from Escherichia coli catalyzed the formation of JA-amino acid conjugates in vitro. Kinetic analysis showed the enzyme has a strong preference for Ile over Leu and Val and it was about 10-fold more active with (+)-7-iso-JA than with its epimer (-)-JA. Leaf wounding rapidly increased JA-Ile 50-fold to about 450 pmol g(-1) FW at 30 min after wounding, while conjugates with Leu, Phe, Val and Met were only marginally increased or not detected. Nearly all of the endogenous JA-Ile was the bioactive epimer (+)-7-iso-JA-Ile and there was no evidence for its conversion to (-)-JA-Ile up to 6 h after wounding. A transgenic RNAi approach was used to suppress SlJAR1 transcript that reduced JA-Ile accumulation by 50-75%, suggesting that other JA conjugating enzymes may be present. These results show that SlJAR1 synthesizes the bioactive conjugate (+)-7-iso-JA-Ile and this is the predominant isomer accumulated in wounded tomato leaves.

The Role of Jasmonates in the Formation of a Compound of Chalcones and Flavans with Phytoalexin-Like Properties in Mechanically Wounded Scales of Hippeastrum × Hybr. Bulbs

“…Further experiments, including study of JMT expression in mechanically wounded tissues of Hippeastrum, should shed more light on the role of jasmonates during processes leading to achievement of immunity. Recent studies revealed that jasmonoyl-L-isoleucine (JA-Ile) acts as a key jasmonate signal (Suza and Staswick, 2008;Suza et al, 2010), so the role of JA-Ile in the response to wounding in Hippeastrum bulb scales also presents an area for investigation.…”

The genuine ligand of a jasmonic acid receptor

“…Fortunately, JA-levels correlate tightly with levels of JA-Ile even the former compound accumulates up to ten-fold higher levels in A. thaliana, tomato or tobacco. 9,10,11 Surprisingly, the highest biological activity in terms of JA-responses was observed with coronatine ( Fig. 1), a phytotoxine which does not occur in plants, but is formed by several strains of Pseudomonas syringae.…”

“…32 Recently quantitative analysis of (+)-7-iso-JA-Ile the terminal ligand of the JA receptor was shown. 11 Here the derivatization with PFBB performed in the known procedure was done only for 15 min. Consequently, epimerization of isomers could be strongly reduced, and there was no epimerization of (-)-JA-Ile to (+)-7-iso-JA-Ile and most of the JA-Ile of wounded tomato leaves could be stably detected as (+)-7-iso-JA-Ile for several hours.…”

“…Therefore, epimerization of (+)-7-iso-JA-Ile seems not to be an important mechanism to switch off JA signaling. 11 The wound response in terms of JA-induced transcripts declined much earlier than the level of the most bioactive jasmonate conjugate. 33 As suggested recently 11 , this putative discrepancy might be explained by stable accumulation of truncated JAZ proteins at elevated levels of JA-Ile thereby attenuating JA responsive gene expression.…”

Simple, Rapid, and Simultaneous Assay of Multiple Carboxyl Containing Phytohormones in Wounded Tomatoes by UPLC-MS/MS Using Single SPE Purification and Isotope Dilution

“…39,40 The synthesized JA consists of two pairs of enantiomers, (-)-JA and (+)-JA, as well as (+)-7-iso-JA and (-)-7-iso-JA, each of which could not be separated on C18 column due to chiral centers of C-3 and C-7 shown in Fig. S3 (Supporting Information).…”