Jasmonate Research Articles

Interplay between secondary metabolites and plant hormones in silver nitrate-elicited Arabidopsis thaliana plants

Plants produce a myriad of specialized compounds in response to threats such as pathogens or pests and different abiotic factors. The stress-related induction of specialized metabolites can be mimicked using silver nitrate (AgNO3) as an elicitor, which application in conservation agriculture has gained interest. In Arabidopsis thaliana, AgNO3 triggers the accumulation of indole glucosinolates (IGs) and the phytoalexin camalexin as well as pheylpropanoid-derived defensive metabolites such as coumaroylagmatins and scopoletin through a yet unknown mechanism. In this work, the role of jasmonic (JA) and salicylic acid (SA) signaling in the AgNO3-triggered specialized metabolite production was investigated. To attain this objective, AgNO3, MeJA and SA were applied to A. thaliana lines impaired in JA or SA signaling, or affected in the endogenous levels of IGs and AGs. Metabolomics data indicated that AgNO3 elicitation required an intact JA and SA signaling to elicit the metabolic response, although mutants impaired in hormone signaling retained certain capacity to induce specialized metabolites. In turn, plants overproducing or abolishing IGs production had also an altered hormonal signaling response, both in the accumulation of signaling molecules and the molecular response mechanisms (ORA59, PDF1.2, VSP2 and PR1 gene expression), which pointed out to a crosstalk between defense hormones and specialized metabolites. The present work provides evidence of a crosstalk mechanism between JA and SA underlying AgNO3 defense metabolite elicitation in A. thaliana. In this mechanism, IGs would act as retrograde feedback signals dampening the hormonal response; hence, expanding the signaling molecule concept.

Exposure to Light of the Abaxial versus Adaxial Side of Detached Kalanchoë blossfeldiana Leaves Affects Anthocyanin Content and Composition Differently.

The accumulation and composition of anthocyanins in leaves of Kalanchoë blossfeldiana, detached and kept for five days under natural light conditions, were investigated. The presence of fifteen derivatives of cyanidin, petunidin, and delphinidin was found. Changes in the content of each anthocyanin in the leaves before and after exposure to light on the abaxial (naturally upper) and adaxial (naturally lower) sides of the leaves were compared. When the adaxial side was exposed to light, the anthocyanin contents of the leaves did not change. In contrast, when the abaxial side of detached leaves was exposed to light, there was enhanced accumulation of delphinidin-rhamnoside-glucoside, cyanidin-rhamnoside-glucoside, cyanidin-glucoside-glucoside, and two unknown derivatives of petunidin and delphinidin. Application of methyl jasmonate (JA-Me) on the abaxial side exposed to light inhibited the accumulation of these anthocyanins. This effect could probably be due to the presence of these anthocyanins in the epidermal cells of K. blossfeldiana leaves and was visible in the microscopic view of its cross-section. These anthocyanins were directly exposed to JA-Me, leading to inhibition of their formation and/or accumulation. The lack of significant effects of JA-Me on anthocyanin mono- and tri-glycosides may indicate that they are mainly present in the mesophyll tissue of the leaf.

NaWRKY70 is a key regulator of Nicotiana attenuata resistance to Alternaria alternata through regulation of phytohormones and phytoalexins biosynthesis.

Jasmonate (JA) and abscisic acid (ABA) are two major phytohormones involved in pathogen resistance. However, how their biosynthesis is regulated is not well understood. We silenced NaWRKY70 in wild tobacco Nicotiana attenuata and determined its role in regulating genes involved in the production of JA, ABA and the phytoalexin capsidiol in response to the fungal pathogen Alternaria alternata using techniques including electrophoretic mobility shift, chromatin immunoprecipitation, transient overexpression and virus-induced gene silencing. Silencing NaWRKY70 dramatically reduced both basal and A. alternata-induced jasmonoyl-isoleucine (JA-Ile) and ABA. Further evidence showed that NaWRKY70 directly binds to the W-boxes of the promoters of NaAOS and NaJAR4 (JA biosynthesis), NaNCED1 and NaXD1-like (ABA biosynthesis), and NaMPK4 (ABA signaling) to activate their expression, while binding but repressing the expression of NaCYP707A4-like3 (ABA degradation). Additionally, NaWRKY70 regulates capsidiol production through its key enzyme genes NaEASs and NaEAHs, and interacts with its regulator NaERF2-like to enhance their expression, whereas ABA negatively regulates capsidiol biosynthesis. Our results highlight the key role of NaWRKY70 in controlling both JA-Ile and ABA production, as well as capsidiol production, thus providing new insight into the defense mechanism of plant resistance to A. alternata.

Enhancement of broad-spectrum disease resistance in wheat through key genes involved in systemic acquired resistance.

Systemic acquired resistance (SAR) is an inducible disease resistance phenomenon in plant species, providing plants with broad-spectrum resistance to secondary pathogen infections beyond the initial infection site. In Arabidopsis, SAR can be triggered by direct pathogen infection or treatment with the phytohormone salicylic acid (SA), as well as its analogues 2,6-dichloroisonicotinic acid (INA) and benzothiadiazole (BTH). The SA receptor non-expressor of pathogenesis-related protein gene 1 (NPR1) protein serves as a key regulator in controlling SAR signaling transduction. Similarly, in common wheat (Triticum aestivum), pathogen infection or treatment with the SA analogue BTH can induce broad-spectrum resistance to powdery mildew, leaf rust, Fusarium head blight, and other diseases. However, unlike SAR in the model plant Arabidopsis or rice, SAR-like responses in wheat exhibit unique features and regulatory pathways. The acquired resistance (AR) induced by the model pathogen Pseudomonas syringae pv. tomato strain DC3000 is regulated by NPR1, but its effects are limited to the adjacent region of the same leaf and not systemic. On the other hand, the systemic immunity (SI) triggered by Xanthomonas translucens pv. cerealis (Xtc) or Pseudomonas syringae pv. japonica (Psj) is not controlled by NPR1 or SA, but rather closely associated with jasmonate (JA), abscisic acid (ABA), and several transcription factors. Furthermore, the BTH-induced resistance (BIR) partially depends on NPR1 activation, leading to a broader and stronger plant defense response. This paper provides a systematic review of the research progress on SAR in wheat, emphasizes the key regulatory role of NPR1 in wheat SAR, and summarizes the potential of pathogenesis-related protein (PR) genes in genetically modifying wheat to enhance broad-spectrum disease resistance. This review lays an important foundation for further analyzing the molecular mechanism of SAR and genetically improving broad-spectrum disease resistance in wheat.

Plant Growth Regulating Phytohormones: The Potent Targets to Alleviate Abiotic Stress in Crop Plants —A Research Update and the Way Forward

The latest modifying models of global climate have changed to be an unadorned threat to the crops production. An extensive scale of biotic and abiotic stresses frequently impacts crop plants because of their stalkless characteristics. Crop plants failures are principally triggered by abiotic factors such as salt, heat, cold, floods, ultraviolet radiation and drought. For dealing with these harsh conditions, well-established mechanisms have been developed in plants, which perform a pivotal role in comprehending stress signals and assisting ideal development responses. Remarkably, the exploitation of plant growth regulating phytohormones for decreasing the adverse effect of abiotic stress has acquired much attention in current decades. For evasion of stress at various levels, including physiological, molecular, and biochemical, an erudite method is informed to be presented by phytohormones. Thus, labeling these phytohormones plays an important function in plant growth and overall development. Phytohormones can progresses tolerance against abiotic stresses by raising seed germination, seedling growth, root growth, leaf photosynthesis and antioxidant enzymes by dropping the accretion of reactive oxygen species, malonaldehyde, and electrolyte outflow. Current findings focus on the important function of a diversity of phytohormones counting, Abscisic acid (ABA), Salicylic acid (SA), Jasmonates (JA) and Ethylene (ET) in the abiotic stress tolerance improvement of crop plants. The contribution of Cytokinins (CKs), and some other novel phytohormones such as Brassinosteroids and Strigolactones in plant development has been acknowledged under normal and stress conditions. Therefore, this review is desired to recap the new progresses in the knowledge associated to phytohormones and their association in abiotic stresses of expectation, signaling, crosstalk, and the response processes. Therefore, such a review will be helpful in improving the pathway for sustainable agriculture development via involvement of phytohormones in improvement of abiotic stress tolerance of the crop plants.

Quantitative proteomics analysis identified new interacting proteins of JAL30 in Arabidopsis

Jacalin-related lectins (JALs) are a unique group of plant lectins derived from the jacalin protein family, which play important roles in plant defense responses. JAL30/PBP1 (PYK10 binding protein 1) interacts with inactive PYK10, exerting negative regulatory control over the size of the PYK10 complex, which is formed and activated upon insect or pathogen invasion. However, the precise interplay between JAL30 and other components remains elusive. In this study, we found JAL30 as a nucleocytoplasmic protein, but no obvious phenotype was observed in jal30–1 single mutant. Through immunoprecipitation (IP) enrichment combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS), dozens of new JAL30 interacting proteins were found in addition to several reported ones. Gene Ontology (GO) analysis revealed that these interacting proteins were highly related to the wounding and bacterial stimuli, suggesting their potential involvement in the jasmonate (JA) response. Importantly, the expression of JAL30 was induced by MeJA treatment, further highlighting its relevance in plant defense mechanisms. A novel JAL30 interacting protein, ESM1, was identified and its interaction with JAL30 was confirmed by Co-immunoprecipitation. Moreover, ESM1 was found as an O-GlcNAcylated protein, suggesting that JAL30 may possess glycosylated protein binding ability, particularly in O-GlcNAcylated protein and peptide recognition. Overall, our study provides valuable insights into the interacting protein network and biological function of JAL30, demonstrates the interaction between JAL30 and ESM1, and uncovers the potential significance of JAL30 in plant defense system, potentially through its association with PYK10 complex or JA response. SignificanceThe biological functions of lectin proteins, including defense responses, immunity responses, signal transduction, have been well studied. Lectin proteins were also utilized to enrich glycosylated proteins for their specific carbohydrates binding capability. Jacalin-related lectins (JALs) were found to involve in plant defense mechanism. However, it is not yet clear whether JALs could use for enrichment of glycosylated proteins. In this study, we used label-free quantification method to identify interacting proteins of JAL30. A novel interacting protein, ESM1, as an O-GlcNAcylated protein was found. ESM1 has been reported to take part in defense against insect herbivory. Therefore, our findings provided experimental evidence to confirm that JALs have potential to be developed as the bio-tools to enrich glycosylated proteins. Finally, our data not only illustrated the vital biological role of JALs in plants, but also verified unique function of JAL30 in recognizing O-GlcNAcylated proteins.

The MYC2–PUB22–JAZ4 module plays a crucial role in jasmonate signaling in tomato

Jasmonates (JAs), a class of lipid-derived stress hormones, play a crucial role across an array of plant physiological processes and stress responses. Although JA signaling is thought to rely predominantly on the degradation of specific JAZ proteins by SCFCOI1, it remains unclear whether other pathways are involved in the regulation of JAZ protein stability. Here, we report that PUB22, a plant U-box type E3 ubiquitin ligase, plays a critical role in the regulation of plant resistance against Helicoverpa armigera and other JA responses in tomato. Whereas COI1 physically interacts with JAZ1/2/5/7, PUB22 physically interacts with JAZ1/3/4/6. PUB22 ubiquitinates JAZ4 to promote its degradation via the 26S proteasome pathway. Importantly, we observed that pub22 mutants showreduced resistance to H. armigera, whereas jaz4 single mutants and jaz1 jaz3 jaz4 jaz6 quadruple mutants have enhanced resistance. The hypersensitivity of pub22 mutants to herbivores could be partially rescued by JAZ4 mutation. Moreover, we found that expression of PUB22 can be transcriptionally activated by MYC2, thus forming a positive feedback circuit in JA signaling. We noticed that the PUB22–JAZ4 module also regulates other JA responses, including defense against B. cinerea, inhibition of root elongation, and anthocyanin accumulation. Taken together, these results indicate that PUB22 plays a crucial role in plant growth and defense responses, together with COI1-regulated JA signaling, by targeting specific JAZs.

Integrative omic and transgenic analyses reveal methyl jasmonate- and abscisic acid-responsive regulator CwbHLH2 that positively regulates terpenoid biosynthesis in Curcuma wenyujin

Bioactive terpenoids from Curcuma wenyujin (CW), as specialized metabolites, have huge medicinal properties. Accumulating evidence suggested that Jasmonates (JAs) and abscisic acid (ABA) shake hands and coordinately control a wide range of plant growth and defense activities, including the production of specialized metabolites. However, knowledge of how JA and ABA signalings interact to regulate terpenoid biosynthesis (TBS) is limited. In this study, integrative transcriptome and metabolome analyses revealed that exogenous methyl jasmonate (MeJA) and ABA activate the biosynthesis of terpenoids by upregulating the expressions of genes related to the TBS pathway, JA and ABA responses. Most of the differentially changed terpenoids and transcripts were commonly induced by MeJA and ABA. Interactive networks of “gene-gene/metabolite” indicated that CwbHLH2, a MeJA and ABA dual-responsive regulator, is tightly related to terpenoid production. Furthermore, transgenic experiments revealed that overexpression and RNA interference of CwbHLH2 upregulated and downregulated the contents of representative terpenoids in the MeJA- and ABA-treated transgenic hairy roots, respectively, with 1.52–3.06-fold increases and 29.6–68.7% reduction. Importantly, the genetic transformation of CwbHLH2 enhanced the expressions of multiple TBS pathway genes and bidirectionally enlarged the JA and ABA signalings caused by MeJA or ABA, demonstrating that CwbHLH2 plays a critical interrelational role in integrating MeJA- and ABA-induced TBS regulation. Altogether, our results not only advance a new view of the crosstalk between JA and ABA in modulating TBS but also provide a powerful strategy for improving the yield of bioactive terpenoids in CW.

A genetic screen for dominant chloroplast reactive oxygen species signaling mutants reveals life stage-specific singlet oxygen signaling networks.

Plants employ intricate molecular mechanisms to respond to abiotic stresses, which often lead to the accumulation of reactive oxygen species (ROS) within organelles such as chloroplasts. Such ROS can produce stress signals that regulate cellular response mechanisms. One ROS, singlet oxygen (1O2), is predominantly produced in the chloroplast during photosynthesis and can trigger chloroplast degradation, programmed cell death (PCD), and retrograde (organelle-to-nucleus) signaling. However, little is known about the molecular mechanisms involved in these signaling pathways or how many different signaling 1O2 pathways may exist. The Arabidopsis thaliana plastid ferrochelatase two (fc2) mutant conditionally accumulates chloroplast 1O2, making fc2 a valuable genetic system for studying chloroplast 1O2-initiated signaling. Here, we have used activation tagging in a new forward genetic screen to identify eight dominant fc2 activation-tagged (fas) mutations that suppress chloroplast 1O2-initiated PCD. While 1O2-triggered PCD is blocked in all fc2 fas mutants in the adult stage, such cellular degradation in the seedling stage is blocked in only two mutants. This differential blocking of PCD suggests that life-stage-specific 1O2-response pathways exist. In addition to PCD, fas mutations generally reduce 1O2-induced retrograde signals. Furthermore, fas mutants have enhanced tolerance to excess light, a natural mechanism to produce chloroplast 1O2. However, general abiotic stress tolerance was only observed in one fc2 fas mutant (fc2 fas2). Together, this suggests that plants can employ general stress tolerance mechanisms to overcome 1O2 production but that this screen was mostly specific to 1O2 signaling. We also observed that salicylic acid (SA) and jasmonate (JA) stress hormone response marker genes were induced in 1O2-stressed fc2 and generally reduced by fas mutations, suggesting that SA and JA signaling is correlated with active 1O2 signaling and PCD. Together, this work highlights the complexity of 1O2 signaling by demonstrating that multiple pathways may exist and introduces a suite of new 1O2 signaling mutants to investigate the mechanisms controlling chloroplast-initiated degradation, PCD, and retrograde signaling.

The N-terminal α2 helix element is critical for the activity of the rice transcription factor MYC2.

Jasmonates (JAs) are a class of phytohormones that play a crucial role in plant growth, development, and environmental stress responses. Central to JA signaling are the MYC2-type transcription factors, as they activate the expression of JA-responsive genes. We previously used CRISPR-Cas9-based genome editing to engineer rice OsMYC2 and yielded a mutant (myc2-5) with a single amino acid (aa) deletion (75I) outside the known functional domains of the protein. This myc2-5 mutant also showed some JA-deficient phenotypes, promoting us to investigate how 75I deletion affects JA responses. The mutation is found in the α2 helix element at the N-terminal of OsMYC2. The deletion of 75I in OsMYC2 rendered plants deficient in most of the JA responses, including root growth, leaf senescence, spikelet development, and resistance to pathogens and herbivores. Biochemical assays revealed that the 75I deletion markedly reduced OsMYC2 protein accumulation, subsequently diminishing its transcriptional activity. However, the deletion did not influence the protein's subcellular localization, DNA-binding capability, or its interactions with JAZ transcriptional repressors and the Mediator complex subunit MED25. Additionally, the screening of seven other deletions in the α2 helix further reinforces the importance of this protein element. Our results highlight the significance of the α2 helix in the N-terminus for OsMYC2's functionality, primarily through modulating its protein levels. This insight expands our knowledge of JA signaling and opens new avenues for research into the yet-to-be-explored domains of the MYC2 protein, with the potential to tailor JA responses in rice and other plant species.

Current perspectives of lncRNAs in abiotic and biotic stress tolerance in plants.

Abiotic/biotic stresses pose a major threat to agriculture and food security by impacting plant growth, productivity and quality. The discovery of extensive transcription of large RNA transcripts that do not code for proteins, termed long non-coding RNAs (lncRNAs) with sizes larger than 200 nucleotides in length, provides an important new perspective on the centrality of RNA in gene regulation. In plants, lncRNAs are widespread and fulfill multiple biological functions in stress response. In this paper, the research advances on the biological function of lncRNA in plant stress response were summarized, like as Natural Antisense Transcripts (NATs), Competing Endogenous RNAs (ceRNAs) and Chromatin Modification etc. And in plants, lncRNAs act as a key regulatory hub of several phytohormone pathways, integrating abscisic acid (ABA), jasmonate (JA), salicylic acid (SA) and redox signaling in response to many abiotic/biotic stresses. Moreover, conserved sequence motifs and structural motifs enriched within stress-responsive lncRNAs may also be responsible for the stress-responsive functions of lncRNAs, it will provide a new focus and strategy for lncRNA research. Taken together, we highlight the unique role of lncRNAs in integrating plant response to adverse environmental conditions with different aspects of plant growth and development. We envisage that an improved understanding of the mechanisms by which lncRNAs regulate plant stress response may further promote the development of unconventional approaches for breeding stress-resistant crops.

Exploration of a multifunctional biocontrol agent Streptomyces sp. JCK-8055 for the management of apple fire blight.

Apple fire blight, caused by the bacterium Erwinia amylovora, is a devastating disease of apple and pear trees. Biological control methods have attracted much attention from researchers to manage plant diseases as they are eco-friendly and viable alternatives to synthetic pesticides. Herein, we isolated Streptomyces sp. JCK-8055 from the root of pepper and investigated its mechanisms of action against E. amylovora. Streptomyces sp. JCK-8055 produced aureothricin and thiolutin, which antagonistically affect E. amylovora. JCK-8055 and its two active metabolites have a broad-spectrum in vitro activity against various phytopathogenic bacteria and fungi. They also effectively suppressed tomato bacterial wilt and apple fire blight in in vivo experiments. Interestingly, JCK-8055 colonizes roots as a tomato seed coating and induces apple leaf shedding at the abscission zone, ultimately halting the growth of pathogenic bacteria. Additionally, JCK-8055 can produce the plant growth regulation hormone indole-3-acetic acid (IAA) and hydrolytic enzymes, including protease, gelatinase, and cellulase. JCK-8055 treatment also triggered the expression of salicylate (SA) and jasmonate (JA) signaling pathway marker genes, such as PR1, PR2, and PR3. Overall, our findings demonstrate that Streptomyces sp. JCK-8055 can control a wide range of plant diseases, particularly apple fire blight, through a combination of mechanisms such as antibiosis and induced resistance, highlighting its excellent potential as a biocontrol agent. KEY POINTS: • JCK-8055 produces the systemic antimicrobial metabolites, aureothricin, and thiolutin. • JCK-8055 treatment upregulates PR gene expression in apple plants against E. amylovora. • JCK-8055 controls plant diseases with antibiotics and induced resistance.

Carrageenans as biostimulants and bio-elicitors: plant growth and defense responses.

In the context of climate change, the need to ensure food security and safety has taken center stage. Chemical fertilizers and pesticides are traditionally used to achieve higher plant productivity and improved plant protection from biotic stresses. However, the widespread use of fertilizers and pesticides has led to significant risks to human health and the environment, which are further compounded by the emissions of greenhouse gases during fertilizer and pesticide production and application, contributing to global warming and climate change. The naturally occurring sulfated linear polysaccharides obtained from edible red seaweeds (Rhodophyta), carrageenans, could offer climate-friendly substitutes for these inputs due to their bi-functional activities. Carrageenans and their derivatives, known as oligo-carrageenans, facilitate plant growth through a multitude of metabolic courses, including chlorophyll metabolism, carbon fixation, photosynthesis, protein synthesis, secondary metabolite generation, and detoxification of reactive oxygen species. In parallel, these compounds suppress pathogens by their direct antimicrobial activities and/or improve plant resilience against pathogens by modulating biochemical changes via salicylate (SA) and/or jasmonate (JA) and ethylene (ET) signaling pathways, resulting in increased production of secondary metabolites, defense-related proteins, and antioxidants. The present review summarizes the usage of carrageenans for increasing plant development and defense responses to pathogenic challenges under climate change. In addition, the current state of knowledge regarding molecular mechanisms and metabolic alterations in plants during carrageenan-stimulated plant growth and plant disease defense responses has been discussed. This evaluation will highlight the potential use of these new biostimulants in increasing agricultural productivity under climate change.

Cross compatibility and endogenous phytohormone profiles in interspecific hybridization between Iris tectorum and Iris germanica

In order to introduce new valuable trait to other species, the interspecific hybridization is used in ornamental breeding. The success of interspecific hybridization is hindered by incompatibility occurring at various stages of hybridization. To character the barriers of interspecific hybridization between Iris tectorum and Iris germanica cultivars, this study investigated the compatibility of pre-fertilization and post-fertilization, and profiles of endogenous phytohormones in ovary of self-pollination and interspecific hybridization. After pollination, pollen tubes germinated, grew through style, and entered ovules in both self-pollination and interspecific hybridization. Thus, the interspecific incompatibility between I. tectorum and I. germanica cultivars were not caused by pre-fertilization barrier. The observations of embryo and endosperm development revealed that incompatibility of interspecific-hybridization occurred at post-fertilization stage during the development of the embryo. The degeneration of endosperms was observed at 15 days after pollination and no embryo was observed in the interspecific hybridization. The abnormal development of embryos and endosperms indicates that reproductive barriers between I. tectorum and I. germanica cultivars happened at post-fertilization stage. To character the profiles of endogenous phytohormones in the ovary of self-pollination and interspecific hybridization, concentration of auxins, cytokinins (CKs), gibberellins (GAs), abscisic acid (ABA), Jasmonate (JA), salicylic acid (SA), and their derivatives were analyzed by UPLC-ESI-MS/MS. The results showed concentrations of indole-3-acetic acid (IAA) and bioactive free based of CKs were highest in ovary of I. tectorum self-pollination (IT-Self), which has normally developed embryos and endosperms. Four bioactive forms of GAs were identified in this study, while the patterns of their concentration changes were not constant among different materials. Besides, the concentration of ABA was highest in unfertilized ovary of I. tectorum (IT-CK). According to the profiles of endogenous phytohormones, the abnormal development of embryos in interspecific hybridization might be caused by the low concentration of IAA and CKs, proper concentration of these phytohormone could be added into in vitro culture medium to rescue embryos of interspecific hybridization. The investigation of cross compatibility and endogenous phytohormone profiles in this study will provide insight for overcoming the barrier of interspecific hybridization and embryo rescue in Iris genus.

Ca2+/calmodulin-mediated desensitization of glutamate receptors shapes plant systemic wound signalling and anti-herbivore defence.

Plants rely on systemic signalling mechanisms to establish whole-body defence in response to insect and nematode attacks. GLUTAMATE RECEPTOR-LIKE (GLR) genes have been implicated in long-distance transmission of wound signals to initiate the accumulation of the defence hormone jasmonate (JA) at undamaged distal sites. The systemic signalling entails the activation of Ca2+-permeable GLR channels by wound-released glutamate, triggering membrane depolarization and cytosolic Ca2+ influx throughout the whole plant. The systemic electrical and calcium signals rapidly dissipate to restore the resting state, partially due to desensitization of the GLR channels. Here we report the discovery of calmodulin-mediated, Ca2+-dependent desensitization of GLR channels, revealing a negative feedback loop in the orchestration of plant systemic wound responses. A CRISPR-engineered GLR3.3 allele with impaired desensitization showed prolonged systemic electrical signalling and Ca2+ waves, leading to enhanced plant defence against herbivores. Moreover, this Ca2+/calmodulin-mediated desensitization of GLR channels is a highly conserved mechanism in plants, providing a potential target for engineering anti-herbivore defence in crops.

Exogenous application of jasmonates and brassinosteroids alleviates lead toxicity in bamboo by altering biochemical and physiological attributes.

Exogenous application of phytohormones is getting promising results in alleviating abiotic stresses, particularly heavy metal (HMs). Jasmonate (JA) and brassinosteroid (BR) have crosstalk in bamboo plants, reflecting a burgeoning area of investigation. Lead (Pb) is the most common pollutant in the environment, adversely affecting plants and human health. The current study focused on the foliar application of 10µM JA and 10µM BR in both single and combination forms on bamboo plants grown under Pb stress (0, 50, 100, 150µM) with a completely randomized design by four replications. The study found that applying 10µM JA and 10µM BR significantly improves growth and tolerance by reducing oxidative stress, reactive oxygen species including hydrogen peroxide (H2O2, 32.91%), superoxide radicals (O2-•, 33.9%), methylglyoxal (MG, 19%), membrane lipoperoxidation (25.66%), and electrolyte leakage (41.5%) while increasing antioxidant (SOD (18%), POD (13%), CAT (20%), APX (12%), and GR (19%)), non-antioxidant (total phenolics (7%), flavonols (12.3%), and tocopherols (13.8%)), and glyoxylate activity (GLyI (13%), GLyII (19%)), proline content (19%), plant metal chelating capacity (17.3%), photosynthetic pigments (16%), plant growth (10%), and biomass (12%). We found that JA and BR, in concert, boost bamboo species' Pb tolerance by enhancing antioxidant and glyoxalase cycles, ion chelation, and reducing metal translocation and accumulation. This conclusively demonstrates that utilizing a BR-JA combination form at 10µM dose may have the potential to yield optimal efficiency in mitigating oxidative stress in bamboo plants.

Jasmonate: A Hormone of Primary Importance for Temperature Stress Response in Plants.

Temperature is a critical environmental factor that plays a vital role in plant growth and development. Temperatures below or above the optimum ranges lead to cold or heat stress, respectively. Temperature stress retards plant growth and development, and it reduces crop yields. Jasmonates (JAs) are a class of oxylipin phytohormones that play various roles in growth, development, and stress response. In recent years, studies have demonstrated that cold and heat stress affect JA biosynthesis and signaling, and JA plays an important role in the response to temperature stress. Recent studies have provided a large body of information elucidating the mechanisms underlying JA-mediated temperature stress response. In the present review, we present recent advances in understanding the role of JA in the response to cold and heat stress, and how JA interacts with other phytohormones during this process.

Impact of Spraying with the Jasmonic Growth Regulator and Adding Nutrient Solution on the Chemical Properties of Pummelo Seedlings (Shaddock)

The College of Agriculture/Samarra University timber canopy was used for the 1/6/2022–1/6/2023 experiment. JA spraying and Ennne nutrition solution were applied to 54 Pummelo seedlings grafted on orange root to determine their chemical composition. Spraying seedlings with three concentrations of Jasmonates (JA) (0, 5, 10 mg.L-1) and three levels of nitrogen-rich (Ennne) nutrient solution (0, 4, 8 ml.L-1) The first appointment was 6/1/2022, the second 21 days later, and so on for the third date. This study used Randomized Complete Block Desigen (R.C.B.D) design as a factorial experiment with two components (JA and Ennne’s nutritional solution, three replications, two seedlings per experimental unit). Factors and their interactions were examined using SAS and the least significant difference (LSD) at 0.05. The study’s findings: After being sprayed with Jasmonates (JA) growth regulator, especially at a concentration of 10 mg.L-1, the nitrogen, phosphorus, potassium, carbohydrates, and Jasmonic acid content of the leaves increased to 0.49, 1.67, 3.40, and 107.2 mg kg-1, respectively, from the lowest rates seen in the comparison treatment. When compared to the control treatment, which had the lowest rates for nitrogen, phosphorus, potassium, carbohydrates, and Jasmonic acid, the sprayed leaves of plants given Ennne nutrient solution had significantly higher levels of these elements. The treatment G2E2 excelled and gave the highest rate of the leaves’ content of nitrogen, phosphorus, potassium, carbohydrates, and Jasmonic acid due to the dual interaction between jasmonic acid and Ennne nutrient solution, while the treatment G0E0 gave the lowest rate of the aforementioned traits.

Jasmonate activates secondary cell wall biosynthesis through MYC2-MYB46 module.

Formation of secondary cell wall (SCW) is tightly regulated spatiotemporally by various developmental and environmental signals. Successful fine-tuning of the trade-off between SCW biosynthesis and stress responses requires a better understanding of how plant growth is regulated under environmental stress conditions. However, the current understanding of the interplay between environmental signaling and SCW formation is limited. The lipid-derived plant hormone jasmonate (JA) and its derivatives are important signaling components involved in various physiological processes including plant growth, development, and abiotic/biotic stress responses. Recent studies suggest that JA is involved in SCW formation but the signaling pathway has not been studied for how JA regulates SCW formation. We tested this hypothesis using the transcription factor MYB46, a master switch for SCW biosynthesis, and JA treatments. Both the transcript and protein levels of MYB46, a master switch for SCW formation, were significantly increased by JA treatment, resulting in the upregulation of SCW biosynthesis. We then show that this JA-induced upregulation of MYB46 is mediated by MYC2, a central regulator of JA signaling, which binds to the promoter of MYB46. We conclude that this MYC2-MYB46 module is a key component of the plant response to JA in SCW formation.

Rice gene OsUGT75A regulates seedling emergence under deep-sowing conditions

Poor seedling emergence is a challenge for direct seeding of rice under deep-sowing field conditions. Here we reveal that UDP-glucosyltransferase OsUGT75A promotes rice seedling emergence under deep-sowing conditions by increasing shoot length. Expression of OsUGT75A was higher in the middle regions of the shoot and in shoots under deep-sowing conditions. Levels of free abscisic acid (ABA) and jasmonates (JA) were higher in shoots of OsUGT75A mutants than in those of wild-type plants, and OsUGT75A mutants were more sensitive to ABA and JA treatments. Reduced shoot length was attributed to higher ABA INSENSITIVE 3 (OsABI3) expression and lower JASMONATE-ZIM domain protein (OsJAZ) expression in shoots. Shoot extension by OsUGT75A is achieved mainly by promotion of cell elongation. An elite haplotype of OsUGT75A associated with increased shoot length was identified among indica rice accessions. OsUGT75A acts to increase seedling emergence under deep-sowing conditions.