Search Results (45)

Droughts are predicted to intensify with climate change, posing a serious threat to global crop production. Increasing drought tolerance in plants requires an understanding of the underlying mechanisms. This study measured the physiological, phytohormonal and transcriptomic responses to drought in two apple rootstocks to identify drought ‘biomarkers’ and investigated whether the application of acibenzolar-S-methyl (ASM) to the roots could enhance drought tolerance. Two potted-plant trials were conducted on dwarfing (M9) and semi-dwarfing (CG202) apple rootstocks. In both trials, the response patterns in the roots and leaves were compared between irrigated and non-irrigated plants over a 14-day period. In trial 2, ASM was applied 14 days before and immediately before withdrawing irrigation. Drought induced significant decreases in transpiration, photosynthesis and stomatal conductance in both trials. This was accompanied by the accumulation of abscisic acid (ABA) metabolites and the upregulation of ABA pathway transcripts (CYP707A1/A2 and NCED3), a decrease in 12-oxophytodienoic acid (cis-OPDA) and the downregulation of ABA receptor genes (PYL4). The responses to drought were greater in the roots than the leaves, broadly similar across both rootstocks, but differed in strength and timing between the rootstocks. The application of ASM to the roots did not significantly affect the responsiveness to drought in either rootstock. The identified phytohormonal and transcriptomic biomarkers require further validation across a broader range of genotypes. Full article

It is known that nutrient deprivation following detachment can cause non-chilling peel pitting (NCPP) in citrus fruits when stored under a non-stressful environment and that this damage is reduced by pretreating the fruit with ethylene (ETH) (4 d, 10 µL L⁻¹). The present work investigates the effect of this pretreatment on jasmonate (JA) accumulation and transcriptional regulation in mature Navelate oranges (Citrus sinensis L. Osbeck) stored under non-stressful conditions. ETH increased the expression of abundant genes participating in the synthesis of cis-(+)-12-oxo-phytodienoic acid (OPDA), jasmonic acid (JA), and methyl jasmonate (MeJA). ETH also upregulated genes involved in jasmonoyl–isoleucine (JAIle) synthesis (CsJAR1) and decrease (CsCYP94B3 and CYP94C1), and CsSTA2, related to JA sulfation. The levels of these JA metabolites increased during fruit holding in ETH and after shifting them to air, with MeJA accumulation being especially remarkable. Overall, the beneficial effect of ETH on reducing NCPP appears to be related not only to this redirection of OPDA and JA metabolism towards the formation of JA derivatives but also to the regulation of JA signalling. Indeed, the repression of the receptor CsCOI1 and upregulation of various CsJAZs repressors caused by nutrient deprivation, together with the ETH-mediated induction of CsCOI1, CsTOPLESS, and abundant CsJAZs during long-term storage, suggests the occurrence of an ETH-enhanced negative transcriptional regulatory feedback loop in JA metabolism and signalling, by which the susceptibility of detached Navelate oranges to NCPP might be reduced. Full article

12-oxo-phytodienoic acid reductases (OPRs) have been substantiated as pivotal in plant growth and response to biotic and abiotic stresses. However, the functional characterization of OPR genes in the peanut genome remains limited. In this study, we identified a total of 20 OPR genes in a tetraploid cultivar and two diploid peanut species, categorizing them into two subfamilies, OPRI and OPRII. The gene structure and conserved protein motifs within each subfamily were elucidated. Additionally, our findings indicate an uneven chromosomal distribution of peanut OPR genes. Gene duplication events were identified as pivotal in the expansion of the OPR gene family. An analysis of cis-acting elements within OPR gene promoters revealed the presence of numerous phytohormone- and stress-related cis-elements. Furthermore, peanut OPR genes exhibited tissue-specific and stress-inducible expression patterns, underscoring their crucial role in peanut growth and stress response. Additionally, plants overexpressing AhOPR6 exhibited significantly enhanced resistance to salt stress, and the AhOPR6-OE lines demonstrated a higher ability to scavenge reactive oxygen species (ROS). Collectively, these findings offer deeper insights into the roles of peanut OPR genes in stress responses, suggesting that AhOPR6 could serve as a potential candidate gene for improving peanut salt tolerance through genetic transformation. Full article

Sinopodophyllum hexandrum (Royle) Ying, the only species of Sinopodophyllum in Berberidaceae, is an endangered traditional Tibetan medicine. The harsh plateau growth environment makes S. hexandrum tough to breed and meet the global demand for clinical medications such as podophyllotoxin (PTOX) and etoposide. Jasmonic acid (JA) is acknowledged as a key phytohormone that modulates stress responses by activating defense mechanisms and promoting the production of specialized metabolites, which offers valuable insights for developing varieties that are more resilient to stress or yield higher amounts of secondary metabolites. In this study, JA treatment was used as a simulated source of stress to investigate the spatiotemporal changes in phytohormones, such as JA, cis-(+)-12-oxo-10, 15(Z)-phytodienoic acid (cis-(+)-OPDA), and abscisic acid (ABA), and transcriptional regulation following hormonal regulation in intact plants. Some correlations through changes in phytohormone levels and the expression level of related signaling pathway genes were observed to confirm the overall regulatory effect after the JA treatment. Furthermore, the JA treatment caused the differential expression of various genes including transcription factors (TFs), of which the most typical one is myelocytomatosis oncogene like protein 2 (MYC2), ShMYC2_3. Therefore, we proposed that a plant hormone-mediated regulatory network exists endogenously in S. hexandrum, enabling it to respond to JA treatment. This study provides a new direction for the germplasm improvement and the sustainable utilization of S. hexandrum when facing exogenous stimulation. Full article

Cotton aphids (Aphis gossypii Glover) cause harm by feeding on phloem sap and spreading plant viruses to lily. Understanding the mechanisms by which aphids infest lily plants is crucial for effective aphid management and control. In this study, we investigated the activity of antioxidants, integrated nontargeted metabolomes and transcriptomes of lilies infested by cotton aphids to explore the changes in lily leaves. Overall, the results indicated that the catalase (CAT) activity in the leaves of the lily plants was greater than that in the leaves of the control plants. A comprehensive identification of 604 substances was conducted in the leaves. Furthermore, the differentially abundant metabolite analysis revealed the enrichment of phenylalanine metabolism and α-linolenic acid metabolism. Moreover, 3574 differentially expressed genes (DEGs), whose expression tended to increase, were linked to glutathione metabolism and phenylpropanoid biosynthesis. In addition, the integrated analysis revealed that the defensive response of lily leaves to aphids is manifested through antioxidant reactions, phenylpropane and flavonoid biosynthesis, and α-linolenic acid metabolism. Finally, the key metabolites were CAT, glutathione, coumaric acid, and jasmonic acid, along with the key genes chalcone synthase (CHS), phenylalanine ammonia-lyase (PAL), and 12-oxo-phytodienoic acid reductase (OPR). Accordingly, the findings of this research elucidate the molecular and metabolic reactions of A. gossypii in lily plants, offering valuable insights for developing aphid resistance strategies in lily farming. Full article

Some citrus orchards in China often experience nitrogen (N) deficiency. For the first time, targeted metabolomics was used to examine N-deficient effects on hormones in sweet orange (Citrus sinensis (L.) Osbeck cv. Xuegan) leaves and roots. The purpose was to validate the hypothesis that hormones play a role in N deficiency tolerance by regulating root/shoot dry weight ratio (R/S), root system architecture (RSA), and leaf and root senescence. N deficiency-induced decreases in gibberellins and indole-3-acetic acid (IAA) levels and increases in cis(+)-12-oxophytodienoic acid (OPDA) levels, ethylene production, and salicylic acid (SA) biosynthesis might contribute to reduced growth and accelerated senescence in leaves. The increased ethylene formation in N-deficient leaves might be caused by increased 1-aminocyclopropanecarboxylic acid and OPDA and decreased abscisic acid (ABA). N deficiency increased R/S, altered RSA, and delayed root senescence by lowering cytokinins, jasmonic acid, OPDA, and ABA levels and ethylene and SA biosynthesis, increasing 5-deoxystrigol levels, and maintaining IAA and gibberellin homeostasis. The unchanged IAA concentration in N-deficient roots involved increased leaf-to-root IAA transport. The different responses of leaf and root hormones to N deficiency might be involved in the regulation of R/S, RSA, and leaf and root senescence, thus improving N use efficiency, N remobilization efficiency, and the ability to acquire N, and hence conferring N deficiency tolerance. Full article

Abiotic stress is a limiting factor in peanut production. Peanut is an important oil crop and cash crop in China. Peanut yield is vulnerable to abiotic stress due to its seeds grown underground. Jasmonic acid (JA) is essential for plant growth and defense against adversity stresses. However, the regulation and mechanism of the jasmonic acid biosynthesis pathway on peanut defense against abiotic stresses are still limitedly understood. In this study, a total of 64 genes encoding key enzymes of JA biosynthesis were identified and classified into lipoxygenases (AhLOXs), alleno oxide synthases (AhAOSs), allene oxide cyclases (AhAOCs), and 12-oxo-phytodienoic acid reductases (AhOPRs) according to gene structure, conserved motif, and phylogenetic feature. A cis-regulatory element analysis indicated that some of the genes contained stress responsive and hormone responsive elements. In addition to proteins involved in JA biosynthesis and signaling, they also interacted with proteins involved in lipid biosynthesis and stress response. Sixteen putative Ah-miRNAs were identified from four families targeting 35 key genes of JA biosynthesis. A tissue expression pattern analysis revealed that AhLOX2 was the highest expressed in leaf tissues, and AhLOX32 was the highest expressed in shoot, root, and nodule tissues. AhLOX16, AhOPR1, and AhOPR3 were up-regulated under drought stress. AhLOX16, AhAOS3, AhOPR1, and AhAOC4 had elevated transcript levels in response to cold stress. AhLOX5, AhLOX16, AhAOC3, AhOPR1, and AhOPR3 were up-regulated for expression under salt stress. Our study could provide a reference for the study of the abiotic stress resistance mechanism in peanut. Full article

Pinellia ternata is a medicinal plant that has important pharmacological value, and the bulbils serve as the primary reproductive organ; however, the mechanisms underlying bulbil initiation remain unclear. Here, we characterized bulbil development via histological, transcriptomic, and targeted metabolomic analyses to unearth the intricate relationship between hormones, genes, and bulbil development. The results show that the bulbils initiate growth from the leaf axillary meristem (AM). In this stage, jasmonic acid (JA), abscisic acid (ABA), isopentenyl adenosine (IPA), and salicylic acid (SA) were highly enriched, while indole-3-acetic acid (IAA), zeatin, methyl jasmonate (MeJA), and 5-dexoxystrigol (5-DS) were notably decreased. Through OPLS-DA analysis, SA has emerged as the most crucial factor in initiating and positively regulating bulbil formation. Furthermore, a strong association between IPA and SA was observed during bulbil initiation. The transcriptional changes in IPT (Isopentenyltransferase), CRE1 (Cytokinin Response 1), A-ARR (Type-A Arabidopsis Response Regulator), B-ARR (Type-B Arabidopsis Response Regulator), AUX1 (Auxin Resistant 1), ARF (Auxin Response Factor), AUX/IAA (Auxin/Indole-3-acetic acid), GH3 (Gretchen Hagen 3), SAUR (Small Auxin Up RNA), GA2ox (Gibberellin 2-oxidase), GA20ox (Gibberellin 20-oxidase), AOS (Allene oxide synthase), AOC (Allene oxide cyclase), OPR (Oxophytodienoate Reductase), JMT (JA carboxy l Methyltransferase), COI1 (Coronatine Insensitive 1), JAZ (Jasmonate ZIM-domain), MYC2 (Myelocytomatosis 2), D27 (DWARF27), SMAX (Suppressor of MAX2), PAL (Phenylalanine Ammonia-Lyase), ICS (Isochorismate Synthase), NPR1 (Non-expressor of Pathogenesis-related Genes1), TGA (TGACG Sequence-specific Binding), PR-1 (Pathogenesis-related), MCSU (Molybdenium Cofactor Sulfurase), PP2C (Protein Phosphatase 2C), and SnRK (Sucrose Non-fermenting-related Protein Kinase 2) were highly correlated with hormone concentrations, indicating that bulbil initiation is coordinately controlled by multiple phytohormones. Notably, eight TFs (transcription factors) that regulate AM initiation have been identified as pivotal regulators of bulbil formation. Among these, WUS (WUSCHEL), CLV (CLAVATA), ATH1 (Arabidopsis Thaliana Homeobox Gene 1), and RAX (Regulator of Axillary meristems) have been observed to exhibit elevated expression levels. Conversely, LEAFY demonstrated contrasting expression patterns. The intricate expression profiles of these TFs are closely associated with the upregulated expression of KNOX(KNOTTED-like homeobox), suggesting a intricate regulatory network underlying the complex process of bulbil initiation. This study offers a profound understanding of the bulbil initiation process and could potentially aid in refining molecular breeding techniques specific to P. ternata. Full article

The recent dominance of Adelphocoris suturalis Jakovlev as the primary cotton field pest in Bt-cotton-cultivated areas has generated significant interest in cotton pest control research. This study addresses the limited understanding of cotton defense mechanisms triggered by A. suturalis feeding. Utilizing LC-QTOF-MS, we analyzed cotton metabolomic changes induced by A. suturalis, and identified 496 differential positive ions (374 upregulated, 122 downregulated) across 11 categories, such as terpenoids, alkaloids, phenylpropanoids, flavonoids, isoflavones, etc. Subsequent iTRAQ-LC-MS/MS analysis of the cotton proteome revealed 1569 differential proteins enriched in 35 metabolic pathways. Integrated metabolome and proteome analysis highlighted significant upregulation of 17 (89%) proteases in the α-linolenic acid (ALA) metabolism pathway, concomitant with a significant increase in 14 (88%) associated metabolites. Conversely, 19 (73%) proteases in the fructose and mannose biosynthesis pathway were downregulated, with 7 (27%) upregulated proteases corresponding to the downregulation of 8 pathway-associated metabolites. Expression analysis of key regulators in the ALA pathway, including allene oxidase synthase (AOS), phospholipase A (PLA), allene oxidative cyclase (AOC), and 12-oxophytodienoate reductase3 (OPR3), demonstrated significant responses to A. suturalis feeding. Finally, this study pioneers the exploration of molecular mechanisms in the plant–insect relationship, thereby offering insights into potential novel control strategies against this cotton pest. Full article

Extensive genome structure variations, such as copy number variations (CNVs) and presence/absence variations, are the basis for the remarkable genetic diversity of maize; however, the effect of CNVs on maize herbivory defense remains largely underexplored. Here, we report that the naturally occurring duplication of the maize 9-lipoxygenase gene ZmLOX5 leads to increased resistance of maize to herbivory by fall armyworms (FAWs). Previously, we showed that ZmLOX5-derived oxylipins are required for defense against chewing insect herbivores and identified several inbred lines, including Yu796, that contained duplicated CNVs of ZmLOX5, referred to as Yu796-2×LOX5. To test whether introgression of the Yu796-2×LOX5 locus into a herbivore-susceptible B73 background that contains a single ZmLOX5 gene is a feasible approach to increase resistance, we generated a series of near-isogenic lines that contained either two, one, or zero copies of the Yu796-2×LOX5 locus in the B73 background via six backcrosses (BC6). Droplet digital PCR (ddPCR) confirmed the successful introgression of the Yu796-2×LOX5 locus in B73. The resulting B73-2×LOX5 inbred line displayed increased resistance against FAW, associated with increased expression of ZmLOX5, increased wound-induced production of its primary oxylipin product, the α-ketol, 9-hydroxy-10-oxo-12(Z),15(Z)-octadecadienoic acid (9,10-KODA), and the downstream defense hormones regulated by this molecule, 12-oxo-phytodienoic acid (12-OPDA) and abscisic acid (ABA). Surprisingly, wound-induced JA-Ile production was not increased in B73-2×LOX5, resulting from the increased JA catabolism. Furthermore, B73-2×LOX5 displayed reduced water loss in response to drought stress, likely due to increased ABA and 12-OPDA content. Taken together, this study revealed that the duplicated CNV of ZmLOX5 quantitively contributes to maize antiherbivore defense and presents proof-of-concept evidence that the introgression of naturally occurring duplicated CNVs of a defensive gene into productive but susceptible crop varieties is a feasible breeding approach for enhancing plant resistance to herbivory and tolerance to abiotic stress. Full article

Plastid-encoded RNA polymerase (PEP) forms a multisubunit complex in operating chloroplasts, where PEP subunits and a sigma factor are tightly associated with 12 additional nuclear-encoded proteins. Mutants with disrupted genes encoding PEP-associated proteins (PAPs) provide unique tools for deciphering mutual relationships among phytohormones. A block of chloroplast biogenesis in Arabidopsis pap mutants specifying highly altered metabolism in white tissues induced dramatic fluctuations in the content of major phytohormones and their metabolic genes, whereas hormone signaling circuits mostly remained functional. Reprogramming of the expression of biosynthetic and metabolic genes contributed to a greatly increased content of salicylic acid (SA) and a concomitant decrease in 1-aminocyclopropane-1-carboxylic acid (ACC) and oxophytodienoic acid (OPDA), precursors of ethylene and jasmonic acid, respectively, in parallel to reduced levels of abscisic acid (ABA). The lack of differences in the free levels of indole-3-acetic acid (IAA) between the pap mutants and wild-type plants was accompanied by fluctuations in the contents of IAA precursors and conjugated forms as well as multilayered changes in the expression of IAA metabolic genes. Along with cytokinin (CK) overproduction, all of these compensatory changes aim to balance plant growth and defense systems to ensure viability under highly modulated conditions. Full article

Plant nutrition is connected to defense against insect herbivores, but the exact mechanism underlying the effect of the nitrogen (N) supply on the anti-herbivore capacity of eggplants (Solanum melongena) has not been studied in detail. Therefore, we examined the impact of low (LN, 0.5 mM) and high (HN, 5 mM) nitrate levels on eggplant resistance against the western flower thrips Frankliniella occidentalis (WFT), a major destructive eggplant pest. Our results showed that LN plants displayed enhanced defense responses to WFT compared to HN plants. This included increased transcript levels of key genes in the jasmonic acid (JA) pathway, the accumulation of JA-amido conjugates (jasmonoyl-isoleucine, jasmonoyl-phenylalanine, and jasmonoyl-valine), JA precursor (12-oxophytodienoic acid), and methyl jasmonate, higher transcript levels of defense marker genes (MPK3, MPK7, and WRKY53), and increased activities of polyphenol oxidase and peroxidase upon a WFT attack. Our findings suggest that N deficiency can prime JA-mediated defense responses in eggplants, resulting in increased anti-herbivore resistance. Full article

In light of recent climate change, with its rising temperatures and precipitation changes, we are facing the need to increase the valuable crop’s tolerance against unfavorable environmental conditions. Emmer wheat is a cereal crop with high nutritional value. We investigated the possibility of improving the stress tolerance of emmer wheat by activating the synthesis of the stress hormone jasmonate by overexpressing two genes of the jasmonate biosynthetic pathway from Arabidopsis thaliana, ALLENE OXIDE SYNTHASE (AtAOS) and OXOPHYTODIENOATE REDUCTASE 3 (AtOPR3). Analyses of jasmonates in intact and mechanically wounded leaves of non-transgenic and transgenic plants showed that the overexpression of each of the two genes resulted in increased wounding-induced levels of jasmonic acid and jasmonate-isoleucine. Against all expectations, the overexpression of AtAOS, encoding a chloroplast-localized enzyme, does not lead to an increased level of the chloroplast-formed 12-oxo-phytodienoic acid (OPDA), suggesting an effective conversion of OPDA to downstream products in wounded emmer wheat leaves. Transgenic plants overexpressing AtAOS or AtOPR3 with increased jasmonate levels show a similar phenotype, manifested by shortening of the first and second leaves and elongation of the fourth leaf, as well as increased tolerance to osmotic stress induced by the presence of the polyethylene glycol (PEG) 6000. Full article

12-oxo-phytodienoic acid (OPDA) is a primary precursor of jasmonates, able to trigger autonomous signaling cascades that activate and fine-tune plant defense responses, as well as growth and development. However, its mechanism of actions remains largely elusive. Here we describe a dual-function messenger of OPDA signaling, reduced glutathione (GSH), that cross-regulates photosynthesis machinery and stress protection/adaptation in concert, optimizing plant plasticity and survival potential. Under stress conditions, the rapid induction of OPDA production stimulates GSH accumulation in the chloroplasts, and in turn leads to protein S-glutathionylation in modulating the structure and function of redox-sensitive enzymes such as 2-cysteine (Cys) peroxiredoxin A (2CPA), a recycler in the water–water cycle. GSH exchanges thiol-disulfides with the resolving Cys^R₁₇₅, while donating an electron (e⁻, H⁺) to the peroxidatic Cys^P₅₃, of 2CPA, which revives its reductase activity and fosters peroxide detoxification in photosynthesis. The electron flow protects photosynthetic processes (decreased total non-photochemical quenching, NPQ_(T)) and maintains its efficiency (increased photosystem II quantum yield, Φ_II). On the other hand, GSH also prompts retrograde signaling from the chloroplasts to the nucleus in adjusting OPDA-responsive gene expressions such as Glutathione S-Transferase 6 (GST6) and GST8, and actuating defense responses against various ecological constraints such as salinity, excess oxidants and light, as well as mechanical wounding. We thus propose that OPDA regulates a unique metabolic switch that interfaces light and defense signaling, where it links cellular and environmental cues to a multitude of plant physiological, e.g., growth, development, recovery, and acclimation, processes. Full article

Jasmonates (JAs), including jasmonic acid (JA), its precursor 12-oxo-phytodienoic acid (OPDA) and its derivatives jasmonoyl-isoleucine (JA-Ile), methyl jasmonate (MeJA), cis-jasmone (CJ) and other oxylipins, are important in the regulation of a range of ecological interactions of plants with their abiotic and particularly their biotic environments. Plant secondary/specialized metabolites play critical roles in implementing these ecological functions of JAs. Pathway and transcriptional regulation analyses have established a central role of JA-Ile-mediated core signaling in promoting the biosynthesis of a great diversity of secondary metabolites. Here, we summarized the advances in JAs-induced secondary metabolites, particularly in secondary metabolites induced by OPDA and volatile organic compounds (VOCs) induced by CJ through signaling independent of JA-Ile. The roles of JAs in integrating and coordinating the primary and secondary metabolism, thereby orchestrating plant growth–defense tradeoffs, were highlighted and discussed. Finally, we provided perspectives on the improvement of the adaptability and resilience of plants to changing environments and the production of valuable phytochemicals by exploiting JAs-regulated secondary metabolites. Full article