Jasmonate Accumulation Research Articles

CHH methylation of genes associated with fatty acid and jasmonate biosynthesis contributes to cold tolerance in autotetraploids of Poncirus trifoliata.

Polyploids have elevated stress tolerance, but the underlying mechanisms remain largely elusive. In this study, we showed that naturally occurring tetraploid plants of trifoliate orange (Poncirus trifoliata (L.) Raf.) exhibited enhanced cold tolerance relative to their diploid progenitors. Transcriptome analysis revealed that whole-genome duplication was associated with higher expression levels of a range of well-characterized cold stress-responsive genes. Global DNA methylation profiling demonstrated that the tetraploids underwent more extensive DNA demethylation in comparison with the diploids under cold stress. CHH methylation in the promoters was associated with up-regulation of related genes, whereas CG, CHG, and CHH methylation in the 3'-regions was relevant to gene down-regulation. Of note, genes involved in unsaturated fatty acids (UFAs) and jasmonate (JA) biosynthesis in the tetraploids displayed different CHH methylation in the gene flanking regions and were prominently up-regulated, consistent with greater accumulation of UFAs and JA when exposed to the cold stress. Collectively, our findings explored the difference in cold stress response between diploids and tetraploids at both transcriptional and epigenetic levels, and gained new insight into the molecular mechanisms underlying enhanced cold tolerance of the tetraploid. These results contribute to uncovering a novel regulatory role of DNA methylation in better cold tolerance of polyploids.

Herbivore-induced Ca2+ signals trigger a jasmonate burst by activating ERF16-mediated expression in tomato.

Herbivory severely affects plant growth, posing a threat to crop production. Calcium ion (Ca2+ ) signaling and accumulation of jasmonates (JAs) are activated in plant response to herbivore attack, leading to the expression of defense pathways. However, little is known about how the Ca2+ signal modulates JA biosynthesis. We used diverse techniques, including CRISPR/Cas9, UPLC-MS/MS and molecular biology methods to explore the role of ETHYLENE RESPONSE FACTOR 16 in Ca2+ signal-triggered JA burst during herbivore defense in tomato. Here we show that simulated herbivory induces GLUTAMATE RECEPTOR LIKE3.3/3.5 (GLR3.3/3.5)-dependent increases in electrical activity, Ca2+ influx and increases the abundance of CALMODULIN2 (CaM2) and ERF16 transcripts in tomato. The interaction between CaM2 and ERF16 promotes JA biosynthesis by enhancing the transcriptional activity of ERF16, which increases the activation of ERF16 expression and causes expression of LIPOXYGENASE D (LOXD), AOC and 12-OXO-PHYTODIENOIC ACID REDUCTASE 3 (OPR3), the key genes in JA biosynthesis. Mutation of CaM2 results in decreased JA accumulation, together with the expression of JA biosynthesis-related genes, leading to reduced resistance to the cotton bollworm Helicoverpa armigera. These findings reveal a molecular mechanism underpinning the Ca2+ signal-initiated systemic JA burst and emphasize the pivotal role of Ca2+ signal/ERF16 crosstalk in herbivore defense.

SlMYC2 mediates stomatal movement in response to drought stress by repressing SlCHS1 expression.

Drought stress limits plant development and reproduction. Multiple mechanisms in plants are activated to respond to stress. The MYC2 transcription factor is a core regulator of the jasmonate (JA) pathway and plays a vital role in the crosstalk between abscisic acid (ABA) and JA. In this study, we found that SlMYC2 responded to drought stress and regulated stomatal aperture in tomato (Solanum lycopersicum). Overexpression of SlMYC2 repressed SlCHS1 expression and decreased the flavonol content, increased the reactive oxygen species (ROS) content in guard cells and promoted the accumulation of JA and ABA in leaves. Additionally, silencing the SlCHS1 gene produced a phenotype that was similar to that of the MYC2-overexpressing (MYC2-OE) strain, especially in terms of stomatal dynamics and ROS levels. Finally, we confirmed that SlMYC2 directly repressed the expression of SlCHS1. Our study revealed that SlMYC2 drove stomatal closure by modulating the accumulation of flavonol and the JA and ABA contents, helping us decipher the mechanism of stomatal movement under drought stress.

SQUINT Positively Regulates Resistance to the Pathogen Botrytis cinerea via miR156-SPL9 Module in Arabidopsis.

SQUINT (SQN) regulates plant maturation by promoting the activity of miR156, which functions primarily in the miR156-SQUAMOSA PROMOTER BINDING PROTEIN-LIKE9 (SPL9) module regulating plant growth and development. Here, we show that SQN acts in the jasmonate (JA) pathway, a major signaling pathway regulating plant responses to insect herbivory and pathogen infection. Arabidopsis thaliana sqn mutants showed elevated sensitivity to the necrotrophic fungus Botrytis cinerea compared with wild type. However, SQN is not involved in the early pattern-triggered immunity response often triggered by fungal attack. Rather, SQN positively regulates the JA pathway, as sqn loss-of-function mutants treated with B. cinerea showed reduced JA accumulation, JA response and sensitivity to JA. Furthermore, the miR156-SPL9 module regulates plant resistance to B. cinerea: mir156 mutant, and SPL9 overexpression plants displayed elevated sensitivity to B. cinerea. Moreover, constitutively expressing miR156a or reducing SPL9 expression in the sqn-1 mutant restored the sensitivity of Arabidopsis to B. cinerea and JA responses. These results suggest that SQN positively modulates plant resistance to B. cinerea through the JA pathway, and the miR156-SPL9 module functions as a bridge between SQN and JA to mediate plant resistance to this pathogen.

On the initiation of jasmonate biosynthesis in wounded leaves.

The basal level of the plant defense hormone jasmonate (JA) in unstressed leaves is low, but wounding causes its near instantaneous increase. How JA biosynthesis is initiated is uncertain, but the lipolysis step that generates fatty acid precursors is generally considered to be the first step. Here, we used a series of physiological, pharmacological, genetic, and kinetic analyses of gene expression and hormone profiling to demonstrate that the early spiking of JA upon wounding does not depend on the expression of JA biosynthetic genes in Arabidopsis (Arabidopsis thaliana). Using a transgenic system, we showed how decoupling the responses to wounding and JA prevents the perpetual synthesis of JA in wounded leaves. We then used DEFECTIVE IN ANTHER DEHISCENCE1 (DAD1) as a model wound-responsive lipase to demonstrate that although its transient expression in leaves can elicit JA biosynthesis to a low level, an additional level of activation is triggered by wounding, which causes massive accumulation of JA. This wound-triggered boosting effect of DAD1-mediated JA synthesis can happen directly in damaged leaves or indirectly in undamaged remote leaves by the systemically transmitted wound signal. Finally, protein stability of DAD1 was influenced by wounding, α-linolenic acid, and mutation in its catalytic site. Together, the data support mechanisms that are independent of gene transcription and translation to initiate the rapid JA burst in wounded leaves and demonstrate how transient expression of the lipase can be used to reveal changes occurring at the level of activity and stability of the key lipolytic step.

Exploring the Effect of Methyl Jasmonate on the Expression of microRNAs Involved in Biosynthesis of Active Compounds of Rosemary Cell Suspension Cultures through RNA-Sequencing.

Our aim in the experiment was to study the effects of methyl jasmonates (MeJA) on the active compounds of rosemary suspension cells, the metabolites’ change of contents under different concentrations of MeJA, including 0 (CK), 10 (M10), 50 (M50) and 100 μM MeJA (M100). The results demonstrated that MeJA treatments promoted the accumulation of rosmarinic acid (RA), carnosic acid (CA), flavonoids, jasmonate (JA), gibberellin (GA), and auxin (IAA); but reduced the accumulations of abscisic acid (ABA), salicylic acid (SA), and aspartate (Asp). In addition, 50 and 100 μM MeJA promoted the accumulation of alanine (Ala) and glutamate (Glu), and 50 μM MeJA promoted the accumulation of linoleic acid and alpha-linolenic acid in rosemary suspension cells. Comparative RNA-sequencing analysis of different concentrations of MeJA showed that a total of 30, 61, and 39 miRNAs were differentially expressed in the comparisons of CKvsM10, CKvsM50, CKvsM100, respectively. The analysis of the target genes of the differentially expressed miRNAs showed that plant hormone signal transduction, linoleic acid, and alpha-linolenic acid metabolism-related genes were significantly enriched. In addition, we found that miR160a-5p target ARF, miR171d_1 and miR171f_3 target DELLA, miR171b-3p target ETR, and miR156a target BRI1, which played a key role in rosemary suspension cells under MeJA treatments. qRT-PCR of 12 differentially expressed miRNAs and their target genes showed a high correlation between the RNA-seq and the qRT-PCR result. Amplification culture of rosemary suspension cells in a 5 L stirred bioreactor showed that cell biomass accumulation in the bioreactor was less than that in the shake flask under the same conditions, and the whole cultivation period was extended to 14 d. Taken together, MeJA promoted the synthesis of the active compounds in rosemary suspension cells in a wide concentration range via concentration-dependent differential expression patterns. This study provided an overall view of the miRNAs responding to MeJA in rosemary.

Volatile Signals From Guava Plants Prime Defense Signaling and Increase Jasmonate-Dependent Herbivore Resistance in Neighboring Citrus Plants.

Intercropping can reduce agricultural pest incidence and represents an important sustainable alternative to conventional pest control methods. Citrus intercropped with guava (Psidium guajava L.) has a lower incidence of Asian citrus psyllid (ACP, Diaphorina citri Kuwayama) and huanglongbing disease (HLB), but the mechanisms are still unknown. In this study, we tested whether volatile organic compounds (VOCs) emitted by guava plants play a role in plant–plant communications and trigger defense responses in sweet orange (Citrus sinensis L. Osbeck) in the laboratory. The results showed that the behavioral preference and developmental performance of ACP on citrus plants that were exposed to guava VOCs were suppressed. The expression of defense-related pathways involved in early signaling, jasmonate (JA) biosynthesis, protease inhibitor (PI), terpenoid, phenylpropanoid, and flavonoid biosynthesis was induced in guava VOC-exposed citrus plants. Headspace analysis revealed that guava plants constitutively emit high levels of (E)-β-caryophyllene and (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT), which can induce the accumulation of JA and promote stronger defense responses of citrus to ACP feeding. In addition, exposure to guava VOCs also increased the indirect defense of citrus by attracting the parasitic wasp Tamarixia radiata. Together, our findings indicate that citrus plants can eavesdrop on the VOC cues emitted by neighboring intact guava plants to boost their JA-dependent anti-herbivore activities. The knowledge gained from this study will provide mechanisms underlying citrus-guava intercropping for the ecological management of insect pests.

The acceleration of yellow lupine flower abscission by jasmonates is accompanied by lipid-related events in abscission zone cells

Yellow lupine is an economically important crop. This species has been used as a great model for abscission processes for several years due to extreme flower abortion, which takes place in the abscission zone (AZ). AZ activation involves modifications of cell walls, membranes, and cellular structure. In this paper, we applied physiological, molecular, biochemical, and instrumental methods to explore lipid-associated changes and the possible involvement of lipid-derived phytohormones – jasmonates (JAs) - in flower AZ activation. Our comprehensive analyses revealed that natural abscission is accompanied by the upregulation of peroxidase, which reflects a disruption of redox balance and/or lipids peroxidation in AZ cell membranes. Redox imbalance was confirmed by appearance of malondialdehyde. Lipid-related processes involved the specific localization and increased level and activity of lipase and LOX, enzymes associated with cell membrane rupture, and JA biosynthesis. Lipid-hydrolyzing phospholipase D, implicated previously in abscission, is also found in naturally active AZs. Observed changes are accompanied by the accumulation of jasmonates, both free jasmonic acid and its methyl ester. The JA derivative exhibited higher biological activity than the nonconjugated form. Overall, our study shed new light on the lipid and phytohormonal regulation of AZ functioning supporting a role of JAs during abscission-associated events.

The Mycorrhiza-and Trichoderma-Mediated Elicitation of Secondary Metabolism and Modulation of Phytohormone Profile in Tomato Plants

Arbuscular mycorrhiza and Trichoderma are well-known beneficial fungi whose plant growth promotion and defense elicitation effects are known. However, the molecular and biochemical processes underlying the beneficial effects of these priming microorganisms have not been fully elucidated yet. On this basis, the present work aimed to use metabolomics to dissect comprehensively the modulation of secondary metabolism induced by mycorrhiza and Trichoderma, using tomato as a model plant. To this aim, either mycorrhiza or Trichoderma were applied to tomato roots at transplanting using a commercial formulation and then harvested once the mutualistic relationship was well established. Shoots were analyzed using an MS-based untargeted metabolomics approach, and differential metabolites identified by multivariate statistics were subjected to pathway analysis. Together with promoting plant growth, the treatments induced a broad molecular reprogramming with the phenylpropanoid biosynthetic pathway (including defense phenolics like coumarins and glycosylated anthocyanins) being strongly elicited. An accumulation of auxins, cytokinins, and jasmonate (especially after treatment with Trichoderma) could be observed concerning phytohormone profiles. Overall, the broad and distinctive effects triggered by mycorrhiza and Trichoderma in tomato secondary metabolism supported both plant growth promotion and immunity.

The rice wound-inducible transcription factor RERJ1 sharing same signal transduction pathway with OsMYC2 is necessary for defense response to herbivory and bacterial blight.

This study describes biological functions of the bHLH transcription factor RERJ1 involved in the jasmonate response and the related defense-associated metabolic pathways in rice, with particular focus on deciphering the regulatory mechanisms underlying stress-induced volatile emission and herbivory resistance. RERJ1 is rapidly and drastically induced by wounding and jasmonate treatment but its biological function remains unknown as yet. Here we provide evidence of the biological function of RERJ1 in plant defense, specifically in response to herbivory and pathogen attack, and offer insights into the RERJ1-mediated regulation of metabolic pathways of specialized defense compounds, such as monoterpene linalool, in possible collaboration with OsMYC2-a well-known master regulator in jasmonate signaling. In rice (Oryza sativa L.), the basic helix-loop-helix (bHLH) family transcription factor RERJ1 is induced under environmental stresses, such as wounding and drought, which are closely linked to jasmonate (JA) accumulation. Here, we investigated the biological function of RERJ1 in response to biotic stresses, such as herbivory and pathogen infection, using an RERJ1-defective mutant. Transcriptome analysis of the rerj1-Tos17 mutant revealed that RERJ1 regulated the expression of a typical family of conserved JA-responsive genes (e.g., terpene synthases, proteinase inhibitors, and jasmonate ZIM domain proteins). Upon exposure to armyworm attack, the rerj1-Tos17 mutant exhibited more severe damage than the wildtype, and significant weight gain of the larvae fed on the mutant was observed. Upon Xanthomonas oryzae infection, the rerj1-Tos17 mutant developed more severe symptoms than the wildtype. Among RERJ1-regulated terpene synthases, linalool synthase expression was markedly disrupted and linalool emission after wounding was significantly decreased in the rerj1-Tos17 mutant. RERJ1 appears to interact with OsMYC2-a master regulator of JA signaling-and many OsJAZ proteins, although no obvious epistatic interaction was detected between them at the transcriptional level. These results indicate that RERJ1 is involved in the transcriptional induction of JA-mediated stress-responsive genes via physical association with OsMYC2 and mediates defense against herbivory and bacterial infection through JA signaling.

Drought stress-induced methyl jasmonate accumulation promotes calycosin-7-O-β-d-glucoside production in Astragalus membranaceus adventitious roots

Drought stress-induced methyl jasmonate accumulation promotes calycosin-7-O-β-d-glucoside production in Astragalus membranaceus adventitious roots

Contrasting effect of prey capture on jasmonate accumulation in two genera of aquatic carnivorous plants (Aldrovanda, Utricularia)

Terrestrial carnivorous plants of genera Drosera, Dionaea and Nepenthes within the order Caryophyllales employ jasmonates for the induction of digestive processes in their traps. Here, we focused on two aquatic carnivorous plant genera with different trapping mechanism from distinct families and orders: Aldrovanda (Droseraceae, Caryophyllales) with snap-traps and Utricularia (Lentibulariaceae, Lamiales) with suction traps. Using phytohormone analyses and simple biotest, we asked whether the jasmonates are involved in the activation of carnivorous response similar to that known in traps of terrestrial genera of Droseraceae (Drosera, Dionaea). The results showed that Utricularia, in contrast with Aldrovanda, does not use jasmonates for activation of carnivorous response and is the second genus in Lamiales, which has not co-opted jasmonate signalling for botanical carnivory. On the other hand, the nLC-MS/MS analyses revealed that both genera secreted digestive fluid containing cysteine protease homologous to dionain although the mode of its regulation may differ. Whereas in Utricularia the cysteine protease is present constitutively in digestive fluid, it is induced by prey and exogenous application of jasmonic acid in Aldrovanda.

GmST1, which encodes a sulfotransferase, confers resistance to soybean mosaic virus strains G2 and G3.

Soybean mosaic virus (SMV) is one of the most widespread and devastating viral diseases worldwide. The genetic architecture of qualitative resistance to SMV in soybean remains unclear. Here, the Rsvg2 locus was identified as underlying soybean resistance to SMV by genome-wide association and linkage analyses. Fine mapping results showed that soybean resistance to SMV strains G2 and G3 was controlled by a single dominant gene, GmST1, on chromosome 13, encoding a sulfotransferase (SOT). A key variation at position 506 in the coding region of GmST1 associated with the structure of the encoded SOT and changed SOT activity levels between RSVG2-S and RSVG2-R alleles. In RSVG2-S allele carrier "Hefeng25", the overexpression of GmST1 carrying the RSVG2-R allele from the SMV-resistant line "Dongnong93-046" conferred resistance to SMV strains G2 and G3. Compared to Hefeng25, the accumulation of SMV was decreased in transgenic plants carrying the RSVG2-R allele. SMV infection differentiated both the accumulation of jasmonates and expression patterns of genes involved in jasmonic acid (JA) signalling, biosynthesis and catabolism in RSVG2-R and RSVG2-S allele carriers. This characterization of GmST1 suggests a new scenario explaining soybean resistance to SMV.

Exogenous Methyl Jasmonate Improves Heat Tolerance of Perennial Ryegrass Through Alteration of Osmotic Adjustment, Antioxidant Defense, and Expression of Jasmonic Acid-Responsive Genes.

Perennial ryegrass (Lolium perenne L.) is an important cool-season grass species that is widely cultivated in temperate regions worldwide but usually sensitive to heat stress. Jasmonates (JAs) may have a positive effect on plant tolerance under heat stress. In this study, results showed that exogenous methyl jasmonic acid (MeJA) could significantly improve heat tolerance of perennial ryegrass through alteration of osmotic adjustment, antioxidant defense, and the expression of JA-responsive genes. MeJA-induced heat tolerance was involved in the maintenance of better relative water content (RWC), the decline of chlorophyll (Chl) loss for photosynthetic maintenance, as well as maintained lower electrolyte leakage (EL) and malondialdehyde (MDA) content under heat condition, so as to avoid further damage to plants. Besides, results also indicated that exogenous MeJA treatment could increase the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX), thus enhancing the scavenging ability of reactive oxygen species, alleviating the oxidative damage caused by heat stress. Heat stress and exogenous MeJA upregulated transcript levels of related genes (LpLOX2, LpAOC, LpOPR3, and LpJMT) in JA biosynthetic pathway, which also could enhance the accumulation of JA and MeJA content. Furthermore, some NAC transcription factors and heat shock proteins may play a positive role in enhancing resistance of perennial ryegrass with heat stress.

ANNEXIN1 mediates calcium-dependent systemic defense in Arabidopsis plants upon herbivory and wounding.

Cellular calcium (Ca) transients are endogenous signals involved in local and systemic signaling and defense activation upon environmental stress, including wounding and herbivory. Still, not all Ca2+ channels contributing to the signaling have been identified, nor are their modes of action fully known. Plant annexins are proteins capable of binding to anionic phospholipids and can exhibit Ca channel-like activity. Arabidopsis ANNEXIN1 (ANN1) is suggested to contribute to Ca transport. Here, we report that wounding and simulated-herbivory-induced cytosolic free Ca elevation was impaired in systemic leaves in ann1 loss-of-function plants. We provide evidence for a role of ANN1 in local and systemic defense of plants attacked by herbivorous Spodoptera littoralis larvae. Bioassays identified ANN1 as a positive defense regulator. Spodoptera littoralis feeding on ann1 gained significantly more weight than larvae feeding on wild-type, whereas those feeding on ANN1-overexpressing lines gained less weight. Herbivory and wounding both induced defense-related responses on treated leaves, such as jasmonate accumulation and defense gene expression. These responses remained local and were strongly reduced in systemic leaves in ann1 plants. Our results indicate that ANN1 plays an important role in activation of systemic rather than local defense in plants attacked by herbivorous insects.

Methyl jasmonate mediates melatonin-induced cold tolerance of grafted watermelon plants

Root–shoot communication has a critical role in plant adaptation to environmental stress. Grafting is widely applied to enhance the abiotic stress tolerance of many horticultural crop species; however, the signal transduction mechanism involved in this tolerance remains unknown. Here, we show that pumpkin- or figleaf gourd rootstock-enhanced cold tolerance of watermelon shoots is accompanied by increases in the accumulation of melatonin, methyl jasmonate (MeJA), and hydrogen peroxide (H2O2). Increased melatonin levels in leaves were associated with both increased melatonin in rootstocks and MeJA-induced melatonin biosynthesis in leaves of plants under cold stress. Exogenous melatonin increased the accumulation of MeJA and H2O2 and enhanced cold tolerance, while inhibition of melatonin accumulation attenuated rootstock-induced MeJA and H2O2 accumulation and cold tolerance. MeJA application induced H2O2 accumulation and cold tolerance, but inhibition of JA biosynthesis abolished rootstock- or melatonin-induced H2O2 accumulation and cold tolerance. Additionally, inhibition of H2O2 production attenuated MeJA-induced tolerance to cold stress. Taken together, our results suggest that melatonin is involved in grafting-induced cold tolerance by inducing the accumulation of MeJA and H2O2. MeJA subsequently increases melatonin accumulation, forming a self-amplifying feedback loop that leads to increased H2O2 accumulation and cold tolerance. This study reveals a novel regulatory mechanism of rootstock-induced cold tolerance.

Gas exchange, vine performance and modulation of secondary metabolism in Vitis vinifera L. cv Barbera following long-term nitrogen deficit

Main ConclusionA reprogramming of secondary metabolism to acclimate to nitrogen deficiency was seen in grapevine eliciting an accumulation of strigolactones and jasmonate. This response links with photosynthetic compensation and enhanced ripening.In addition to the metabolism directly related to nitrogen assimilation, long-term nitrogen depletion may affect plant secondary metabolism, in turn affecting grapevine performance. In this work, the effect of nitrogen deficit was investigated in V. vinifera cv. Barbera potted vines following three years of deprivation, using a combination of morpho-physiological assessments and mass spectrometry-based untargeted metabolomics. Plants grown under nitrogen limitation showed reduced growth and even more curtailed yields, lowered SPAD values, and a quite preserved leaf gas exchange, compared to plants grown under non-limiting nitrogen availability. Ripening was decidedly accelerated, and berry composition improved in terms of higher sugar and phenolic contents under nitrogen-limiting conditions. Metabolomics showed the broad involvement of secondary metabolism in acclimation to nitrogen deficiency, including a distinctive modulation of the phytohormone profile. Several nitrogen-containing metabolites were down accumulated under nitrogen-limiting conditions, including alkaloids, glucosinolates, hypoxanthine, and inosine. On the other hand, phenylpropanoids showed an accumulation trend. Concerning the recruitment of hormones, nitrogen deprivation elicited an accumulation of strigolactones and jasmonate. Noteworthy, both strigolactones and jasmonates have been previously related to increased photosynthetic efficiency under abiotic stress. Furthermore, the severe reduction of lateral shoot development we recorded in N-deprived vines is consistent with the accumulation of strigolactones. Overall, our results suggest that nitrogen deprivation induced a rather broad metabolic reprogramming, mainly including secondary metabolism and hormones profile, reflected in the modulation of photosynthetic performance, canopy growth, and possibly fruit quality.

Long non-coding RNAs associate with jasmonate-mediated plant defence against herbivores.

Long non-coding RNA (lncRNA) are important regulators of many biological processes in plants, including defence against pathogens; whether lncRNAs mediate defence against herbivore attack is yet to be explored. With wild tobacco, Nicotiana attenuata, and its well-characterized interactions with herbivores, we identified a total of 1,290 significantly up- or down-regulated lncRNAs in response to a precise herbivore elicitation treatment. Of these, long intergenic non-coding RNAs (lincRNAs) were the most abundant. Based on their expression patterns, these up-regulated lincRNAs were classified as early (<1 hr) or late (>3 hr) responders. The early responding lincRNAs had accumulation patterns that tracked the herbivore-elicited burst of bioactive jasmonates (JAs) and the expression of regulator genes in JA signalling which regulate plant defences against herbivores. Silencing two of these early responders in N. attenuata (JAL1 and JAL3) significantly attenuated the accumulation of JAs, JA-mediated defensives and the plant's resistance to M. sexta attack, suggesting roles in regulating JA-mediated plant defence. By lincRNA sequencing of JA-deficient lines, many late responder lincRNAs were found to be transcriptionally regulated by JA signalling. This study uncovers a new role of lncRNAs in JA-mediated herbivore resistance.

Molecular Mechanism Underlying the Synergetic Effect of Jasmonate on Abscisic Acid Signaling during Seed Germination in Arabidopsis

Abscisic acid (ABA) is known to suppress seed germination and post-germinative growth of Arabidopsis (Arabidopsis thaliana), and jasmonate (JA) enhances ABA function. However, the molecular mechanism underlying the crosstalk between the ABA and JA signaling pathways remains largely elusive. Here, we show that exogenous coronatine, a JA analog structurally similar to the active conjugate jasmonate-isoleucine, significantly enhances the delayed seed germination response to ABA. Disruption of the JA receptor CORONATINE INSENSITIVE1 or accumulation of the JA signaling repressor JASMONATE ZIM-DOMAIN (JAZ) reduced ABA signaling, while jaz mutants enhanced ABA responses. Mechanistic investigations revealed that several JAZ repressors of JA signaling physically interact with ABSCISIC ACID INSENSITIVE3 (ABI3), a critical transcription factor that positively modulates ABA signaling, and that JAZ proteins repress the transcription of ABI3 and ABI5. Further genetic analyses showed that JA activates ABA signaling and requires functional ABI3 and ABI5. Overexpression of ABI3 and ABI5 simultaneously suppressed the ABA-insensitive phenotypes of the coi1-2 mutant and JAZ-accumulating (JAZ-ΔJas) plants. Together, our results reveal a previously uncharacterized signaling module in which JAZ repressors of the JA pathway regulate the ABA-responsive ABI3 and ABI5 transcription factors to integrate JA and ABA signals during seed germination and post-germinative growth.

Red Light Controls Adventitious Root Regeneration by Modulating Hormone Homeostasis in Picea abies Seedlings.

Vegetative propagation relies on the capacity of plants to regenerate de novo adventitious roots (ARs), a quantitative trait controlled by the interaction of endogenous factors, such as hormones and environmental cues among which light plays a central role. However, the physiological and molecular components mediating light cues during AR initiation (ARI) remain largely elusive. Here, we explored the role of red light (RL) on ARI in de-rooted Norway spruce seedlings. We combined investigation of hormone metabolism and gene expression analysis to identify potential signaling pathways. We also performed extensive anatomical characterization to investigate ARI at the cellular level. We showed that in contrast to white light, red light promoted ARI likely by reducing jasmonate (JA) and JA-isoleucine biosynthesis and repressing the accumulation of isopentyl-adenine-type cytokinins. We demonstrated that exogenously applied JA and/or CK inhibit ARI in a dose-dependent manner and found that they possibly act in the same pathway. The negative effect of JA on ARI was confirmed at the histological level. We showed that JA represses the early events of ARI. In conclusion, RL promotes ARI by repressing the accumulation of the wound-induced phytohormones JA and CK.