Synthesis, structural characterization and biological activity of two diastereomeric JA-Ile macrolactones

Abstract

Jasmonates are phytohormones involved in a wide range of plant processes, including growth, development, senescence, and defense. Jasmonoyl-L-isoleucine (JA-Ile, 2), an amino acid conjugate of jasmonic acid (JA, 1), has been identified as a bioactive endogenous jasmonate. However, JA-Ile (2) analogues trigger different responses in the plant. ω-Hydroxylation of the pentenyl side chain leads to the inactive 12-OH-JA-Ile (3) acting as a “stop” signal. On the other hand, a lactone derivative of 12-OH-JA (5) (jasmine ketolactone, JKL) occurs in nature, although with no known biological function. Inspired by the chemical structure of JKL (6) and in order to further explore the potential biological activities of 12-modified JA-Ile derivatives, we synthesized two macrolactones (JA-Ile-lactones (4a) and (4b)) derived from 12-OH-JA-Ile (3). The biological activity of (4a) and (4b) was tested for their ability to elicit nicotine production, a well-known jasmonate dependent secondary metabolite. Both macrolactones showed strong biological activity, inducing nicotine accumulation to a similar extent as methyl jasmonate does in Nicotiana attenuata leaves. Surprisingly, the highest nicotine contents were found in plants treated with the JA-Ile-lactone (4b), which has (3S,7S) configuration at the cyclopentanone not known from natural jasmonates. Macrolactone (4a) is a valuable standard to explore for its occurrence in nature.

Auxin Is Rapidly Induced by Herbivore Attack and Regulates a Subset of Systemic, Jasmonate-Dependent Defenses

“…This transcription factor may therefore represent a target for the integration of IAA and JA signaling. While IAA strongly potentiated the accumulation of stem phenolamides, it had little effect on the accumulation of other JA-dependent secondary metabolites, including nicotine and 7-hydroxygeranyllinalool diterpene glycosides (Machado et al, 2013(Machado et al, , 2016Paschold et al, 2007;Jimenez-Aleman et al, 2015). This result is consistent with earlier studies showing neutral to negative effects of auxin application on nicotine accumulation in Nicotiana spp.…”

Species‐specific regulation of herbivory‐induced defoliation tolerance is associated with jasmonate inducibility

“…A phylogenetic study across 36 Asclepias species uncovered no clear correlation between resistance traits and regrowth ability (Agrawal & Fishbein, ), and evidence is emerging that plants may employ mixed strategies to survive herbivore attack (Núñez‐Farfán, Fornoni, & Valverde, ). At first glance, our results may lead to the conclusion that a negative association between resistance and defoliation tolerance would be very likely for the Solanaceae, as jasmonates regulate resistance traits positively (Jimenez‐Aleman, Machado, Baldwin, & Boland, ) and defoliation tolerance negatively (Jimenez‐Aleman, Machado, Görls, Baldwin, & Boland, ; Machado et al., ). However, while resistance factors are in large part controlled by JA‐Ile, we found strong negative correlations between JA, but not JA‐Ile and defoliation tolerance.…”

Aboveground herbivory induced jasmonates disproportionately reduce plant reproductive potential by facilitating root nematode infestation

“…Soluble sugars and starch were quantified as described elsewhere (Machado, Arce, Ferrieri, Baldwin, & Erb, ; Machado, Baldwin, & Erb, ; Robert et al, ). Nicotine was quantified as described elsewhere (Jimenez‐Aleman, Machado, Baldwin, & Boland, ; Jimenez‐Aleman, Machado, Görls, Baldwin, & Boland, ). For amino acid quantification, 100 mg of ground plant material were extracted in acidified methanol (50% MeOH, 49.5% H 2 O, 0.05% acetic acid).…”