The Rise and Fall of Jasmonate Biological Activities

Abstract

Jasmonates (JAs) constitute a major class of plant regulators that coordinate responses to biotic and abiotic threats and important aspects of plant development. The core biosynthetic pathway converts linolenic acid released from plastid membrane lipids to the cyclopentenone cis-oxo-phytodienoic acid (OPDA) that is further reduced and shortened to jasmonic acid (JA) in peroxisomes. Abundant pools of OPDA esterified to plastid lipids also occur upon stress, mainly in the Arabidopsis genus. Long thought to be the bioactive hormone, JA only gains its pleiotropic hormonal properties upon conjugation into jasmonoyl-isoleucine (JA-Ile). The signaling pathway triggered when JA-Ile promotes the assembly of COI1-JAZ (Coronatine Insensitive 1-JAsmonate Zim domain) co-receptor complexes has been the focus of most recent research in the jasmonate field. In parallel, OPDA and several other JA derivatives are recognized for their separate activities and contribute to the diversity of jasmonate action in plant physiology. We summarize in this chapter the properties of different bioactive JAs and review elements known for their perception and signal transduction. Much progress has also been gained on the enzymatic processes governing JA-Ile removal. Two JA-Ile catabolic pathways, operating through ω-oxidation (cytochromes P450) or conjugate cleavage (amido hydrolases) shape signal dynamics to allow optimal control on defense. JA-Ile turnover not only participates in signal attenuation, but also impact the homeostasis of the entire JA metabolic pathway.

Caterpillars induce jasmonates in flowers and alter plant responses to a second attacker

“…Thus, we quantified the concentration of the phytohormones ABA, SA, JA and the precursor of JA, cis-(+)-12-oxophytodienoic acid (cis-OPDA) (Heitz et al, 2016). In addition, we quantified (+)-7-isojasmonoyl-ʟ-isoleucine ((+)-7-iso-JA-Ile) assumed to be the most active form of JA and (À)-jasmonoyl-ʟ-isoleucine ((À)-JA-Ile), a less active form of JA (Fonseca et al, 2009;Avanci et al, 2010), and we quantified the degradation products of JA that are nonactive: 12-hydroxy-jasmonate (12-OH-JA), 12-hydroxy-jasmonoylisoleucine (12-OH-JA-Ile) and 12-carboxy-jasmonoyl-isoleucine (12-COOH-JA-Ile) (Heitz et al, 2016). Phytohormone concentrations (ng g À1 of dry mass) were quantified for six plant replicates per treatment, and per time point.…”

Stress‐ and pathway‐specific impacts of impaired jasmonoyl‐isoleucine (JA‐Ile) catabolism on defense signalling and biotic stress resistance

“…Another way to repress or terminate jasmonate action is at the metabolic level, either by diverting the flux to hydroxy‐JA rather than to JA‐Ile (Smirnova et al, ) or by modifying JA‐Ile to alleviate its receptor‐binding properties. The characterisation of JA‐Ile catabolic pathways has shed light on hormone homeostasis regulation and has also provided a framework explaining additional complexity in the JA metabolic grid (Heitz et al, ). Two distinct enzymatic pathways are known to modify or degrade JA‐Ile.…”

“…These enzymes act on JA‐Ile and other JA‐amino acid conjugates but also on 12OH‐JA‐Ile generated by CYP94Bs, releasing JA and 12OH‐JA, respectively (Widemann et al, ; Zhang et al, ). The interconnection of the two catabolic pathways generates increased metabolic complexity because many of the above‐mentioned JAs are derived, in fact, from JA‐Ile catabolism (Heitz et al, ; Widemann et al, ). Expression of both JA‐Ile oxidases and amidohydrolases (AH) genes is induced by environmental cues and co‐regulated with the central regulon defined by JA pathway biosynthetic and signalling genes.…”

Gibberellin antagonizes jasmonate‐induced defense against Meloidogyne graminicola in rice

“…Studies involving plant-nematode interactions provide an opportunity to decipher hormone-mediated defense responses in roots. Jasmonate is one of the archetypal hormones involved in plant defense and developmental processes (Glazebrook, 2005;Wasternack & Hause, 2013;Heitz et al, 2016). Previous studies have shown the vital role of JA in basal resistance against the RKN M. graminicola in rice (Nahar et al, 2011), M. javanica and M. incognita in tomato (Cooper et al, 2005;Fujimoto et al, 2011) and M. hapla in Arabidopsis and soybean (Gleason et al, 2016;Hu et al, 2017).…”