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Jasmonates: News on Occurrence, Biosynthesis, Metabolism and Action of an Ancient Group of Signaling Compounds
Jasmonic acid (JA) and its related derivatives are ubiquitously occurring compounds of land plants acting in numerous stress responses and development. Recent studies on evolution of JA and other oxylipins indicated conserved biosynthesis. JA formation is initiated by oxygenation of α-linolenic acid (α-LeA, 18:3) or 16:3 fatty acid of chloroplast membranes leading to 12-oxo-phytodienoic acid (OPDA) as intermediate compound, but in Marchantia polymorpha and Physcomitrella patens, OPDA and some of its derivatives are final products active in a conserved signaling pathway. JA formation and its metabolic conversion take place in chloroplasts, peroxisomes and cytosol, respectively. Metabolites of JA are formed in 12 different pathways leading to active, inactive and partially active compounds. The isoleucine conjugate of JA (JA-Ile) is the ligand of the receptor component COI1 in vascular plants, whereas in the bryophyte M. polymorpha COI1 perceives an OPDA derivative indicating its functionally conserved activity. JA-induced gene expressions in the numerous biotic and abiotic stress responses and development are initiated in a well-studied complex regulation by homeostasis of transcription factors functioning as repressors and activators.
Journal Article
Hydroxylated jasmonates are commonly occurring metabolites of jasmonic acid and contribute to a partial switch-off in jasmonate signaling
In potato 12-hydroxyjasmonic acid (12-OH-JA) is a tuber-inducing compound. Here, it is demonstrated that 12-OH-JA, as well as its sulfated and glucosylated derivatives, are constituents of various organs of many plant species. All accumulate differentially and usually to much higher concentrations than jasmonic acid (JA). In wounded tomato leaves, 12-OH-JA and its sulfated, as well as glucosylated, derivative accumulate after JA, and their diminished accumulation in wounded leaves of the JA-deficient mutants spr2 and acx1 and also a JA-deficient 35S::AOCantisense line suggest their JA-dependent formation. To elucidate how signaling properties of JA/JAME (jasmonic acid methyl ester) are affected by hydroxylation and sulfation, germination and root growth were recorded in the presence of the different jasmonates, indicating that 12-OH-JA and 12-hydroxyjasmonic acid sulfate (12-HSO₄-JA) were not bioactive. Expression analyses for 29 genes showed that expression of wound-inducible genes such as those coding for PROTEINASE INHIBITOR2, POLYPHENOL OXIDASE, THREONINE DEAMINASE or ARGINASE was induced by JAME and less induced or even down-regulated by 12-OH-JA and 12-HSO₄-JA. Almost all genes coding for enzymes in JA biosynthesis were up-regulated by JAME but down-regulated by 12-OH-JA and 12-HSO₄-JA. The data suggest that wound-induced metabolic conversion of JA/JAME into 12-OH-JA alters expression pattern of genes including a switch off in JA signaling for a subset of genes.
Journal Article
The Meloidogyne javanica effector Mj2G02 interferes with jasmonic acid signalling to suppress cell death and promote parasitism in Arabidopsis
Plant‐parasitic nematodes can cause devastating damage to crops. These nematodes secrete effectors that suppress the host immune responses to enhance their survival. In this study, Mj2G02, an effector from Meloidogyne javanica, is described. In situ hybridization and transcriptional analysis showed that Mj2G02 was highly expressed in the early infection stages and exclusively expressed in the nematode subventral oesophageal gland cells. In planta RNA interference targeting Mj2G02 impaired M. javanica parasitism, and Mj2G02‐transgenic Arabidopsis lines displayed more susceptibility to M. javanica. Using an Agrobacterium‐mediated transient expression system and plant immune response assays, we demonstrated that Mj2G02 localized in the plant cell nuclei and could suppress Gpa2/RBP‐1‐induced cell death. Moreover, by RNA‐Seq and quantitative reverse transcription PCR analyses, we showed that Mj2G02 was capable of interfering with the host jasmonic acid (JA) signalling pathway. Multiple jasmonate ZIM‐domain (JAZ) genes were significantly upregulated, whereas the JAR1 gene and four JA‐responsive genes, MYC3, UPI, THI2.1, and WRKY75, were significantly downregulated. In addition, HPLC analysis showed that the endogenous jasmonoyl‐isoleucine (JA‐Ile) level in Mj2G02‐transgenic Arabidopsis lines was significantly decreased compared to that in wildtype plants. Our results indicate that the M. javanica effector Mj2G02 suppresses the plant immune response, therefore facilitating nematode parasitism. This process is probably mediated by a JA‐Ile reduction and JAZ enhancement to repress JA‐responsive genes. The effector Mj2G02 from Meloidogyne javanica reduces JA‐Ile and promotes JAZ proteins to repress JA‐responsive genes and impair the plant immunity.
Journal Article
The MIK2/SCOOP Signaling System Contributes to Arabidopsis Resistance Against Herbivory by Modulating Jasmonate and Indole Glucosinolate Biosynthesis
Initiation of plant immune signaling requires recognition of conserved molecular patterns from microbes and herbivores by plasma membrane-localized pattern recognition receptors. Additionally, plants produce and secrete numerous small peptide hormones, termed phytocytokines, which act as secondary danger signals to modulate immunity. In Arabidopsis, the Brassicae -specific SERINE RICH ENDOGENOUS PEPTIDE (SCOOP) family consists of 14 members that are perceived by the leucine-rich repeat receptor kinase MALE DISCOVERER 1-INTERACTING RECEPTOR LIKE KINASE 2 (MIK2). Recognition of SCOOP peptides elicits generic early signaling responses but knowledge on how and if SCOOPs modulate specific downstream immune defenses is limited. We report here that depletion of MIK2 or the single PROSCOOP12 precursor results in decreased Arabidopsis resistance against the generalist herbivore Spodoptera littoralis but not the specialist Pieris brassicae. Increased performance of S. littoralis on mik2-1 and proscoop12 is accompanied by a diminished accumulation of jasmonic acid, jasmonate-isoleucine and indolic glucosinolates. Additionally, we show transcriptional activation of the PROSCOOP gene family in response to insect herbivory. Our data therefore indicate that perception of endogenous SCOOP peptides by MIK2 modulates the jasmonate pathway and thereby contributes to enhanced defense against a generalist herbivore.
Journal Article
Jasmonates: biosynthesis, perception, signal transduction and action in plant stress response, growth and development. An update to the 2007 review in Annals of Botany
• Background Jasmonates are important regulators in plant responses to biotic and abiotic stresses as well as in development. Synthesized from lipid-constituents, the initially formed jasmonic acid is converted to different metabolites including the conjugate with isoleucine. Important new components of jasmonate signalling including its receptor were identified, providing deeper insight into the role of jasmonate signalling pathways in stress responses and development. • Scope The present review is an update of the review on jasmonates published in this journal in 2007. New data of the last five years are described with emphasis on metabolites of jasmonates, on jasmonate perception and signalling, on cross-talk to other plant hormones and on jasmonate signalling in response to herbivores and pathogens, in symbiotic interactions, in flower development, in root growth and in light perception. • Conclusions The last few years have seen breakthroughs in the identification of JASMONATE ZIM DOMAIN (JAZ) proteins and their interactors such as transcription factors and co-repressors, and the crystallization of the jasmonate receptor as well as of the enzyme conjugating jasmonate to amino acids. Now, the complex nature of networks of jasmonate signalling in stress responses and development including hormone cross-talk can be addressed.
Journal Article
A plant’s balance of growth and defense – revisited
This article is a Commentary on Major et al., 215: 1533–1547.
Journal Article
Jasmonic Acid Signaling Pathway in Response to Abiotic Stresses in Plants
Plants as immovable organisms sense the stressors in their environment and respond to them by means of dedicated stress response pathways. In response to stress, jasmonates (jasmonic acid, its precursors and derivatives), a class of polyunsaturated fatty acid-derived phytohormones, play crucial roles in several biotic and abiotic stresses. As the major immunity hormone, jasmonates participate in numerous signal transduction pathways, including those of gene networks, regulatory proteins, signaling intermediates, and proteins, enzymes, and molecules that act to protect cells from the toxic effects of abiotic stresses. As cellular hubs for integrating informational cues from the environment, jasmonates play significant roles in alleviating salt stress, drought stress, heavy metal toxicity, micronutrient toxicity, freezing stress, ozone stress, CO2 stress, and light stress. Besides these, jasmonates are involved in several developmental and physiological processes throughout the plant life. In this review, we discuss the biosynthesis and signal transduction pathways of the JAs and the roles of these molecules in the plant responses to abiotic stresses.
Journal Article
A non‐JA producing oxophytodienoate reductase functions in salicylic acid‐mediated antagonism with jasmonic acid during pathogen attack
Peroxisome‐localized oxo‐phytodienoic acid (OPDA) reductases (OPR) are enzymes converting 12‐OPDA into jasmonic acid (JA). However, the biochemical and physiological functions of the cytoplasmic non‐JA producing OPRs remain largely unknown. Here, we generated Mutator‐insertional mutants of the maize OPR2 gene and tested its role in resistance to pathogens with distinct lifestyles. Functional analyses showed that the opr2 mutants were more susceptible to the (hemi)biotrophic pathogens Colletotrichum graminicola and Ustilago maydis, but were more resistant to the necrotrophic fungus Cochliobolus heterostrophus. Hormone profiling revealed that increased susceptibility to C. graminicola was associated with decreased salicylic acid (SA) but increased JA levels. Mutation of the JA‐producing lipoxygenase 10 (LOX10) reversed this phenotype in the opr2 mutant background, corroborating the notion that JA promotes susceptibility to this pathogen. Exogenous SA did not rescue normal resistance levels in opr2 mutants, suggesting that this SA‐inducible gene is the key downstream component of the SA‐mediated defences against C. graminicola. Disease assays of the single and double opr2 and lox10 mutants and the JA‐deficient opr7opr8 mutants showed that OPR2 negatively regulates JA biosynthesis, and that JA is required for resistance against C. heterostrophus. Overall, this study uncovers a novel function of a non‐JA producing OPR as a major negative regulator of JA biosynthesis during pathogen infection, a function that leads to its contrasting contribution to either resistance or susceptibility depending on pathogen lifestyle. ZmOPR2 functions as a key component of salicylic acid‐mediated defences via suppressing jasmonic acid biosynthesis during pathogen infection, leading to its contrasting contribution to either resistance or susceptibility depending on pathogen lifestyle.
Journal Article