Jasmonate Treatment Research Articles

A Novel R2R3-MYB Transcription Factor SbMYB12 Positively Regulates Baicalin Biosynthesis in Scutellaria baicalensis Georgi.

Scutellaria baicalensis Georgi is an annual herb from the Scutellaria genus that has been extensively used as a traditional medicine for over 2000 years in China. Baicalin and other flavonoids have been identified as the principal bioactive ingredients. The biosynthetic pathway of baicalin in S. baicalensis has been elucidated; however, the specific functions of R2R3-MYB TF, which regulates baicalin synthesis, has not been well characterized in S. baicalensis to date. Here, a S20 R2R3-MYB TF (SbMYB12), which encodes 263 amino acids with a length of 792 bp, was expressed in all tested tissues (mainly in leaves) and responded to exogenous hormone methyl jasmonate (MeJA) treatment. The overexpression of SbMYB12 significantly promoted the accumulation of flavonoids such as baicalin and wogonoside in S. baicalensis hairy roots. Furthermore, biochemical experiments revealed that SbMYB12 is a nuclear-localized transcription activator that binds to the SbCCL7-4, SbCHI-2, and SbF6H-1 promoters to activate their expression. These results illustrate that SbMYB12 positively regulates the generation of baicalin and wogonoside. In summary, this work revealed a novel S20 R2R3-MYB regulator and enhances our understanding of the transcriptional and regulatory mechanisms of baicalin biosynthesis, as well as sheds new light on metabolic engineering in S. baicalensis.

NtbHLH49, a jasmonate-regulated transcription factor, negatively regulates tobacco responses to Phytophthora nicotianae.

Tobacco black shank caused by Phytophthora nicotianae is a devastating disease that causes huge losses to tobacco production across the world. Investigating the regulatory mechanism of tobacco resistance to P. nicotianae is of great importance for tobacco resistance breeding. The jasmonate (JA) signaling pathway plays a pivotal role in modulating plant pathogen resistance, but the mechanism underlying JA-mediated tobacco resistance to P. nicotianae remains largely unclear. This work explored the P. nicotianae responses of common tobacco cultivar TN90 using plants with RNAi-mediated silencing of NtCOI1 (encoding the perception protein of JA signal), and identified genes involved in this process by comparative transcriptome analyses. Interestingly, the majority of the differentially expressed bHLH transcription factor genes, whose homologs are correlated with JA-signaling, encode AtBPE-like regulators and were up-regulated in NtCOI1-RI plants, implying a negative role in regulating tobacco response to P. nicotianae. A subsequent study on NtbHLH49, a member of this group, showed that it's negatively regulated by JA treatment or P. nicotianae infection, and its protein was localized to the nucleus. Furthermore, overexpression of NtbHLH49 decreased tobacco resistance to P. nicotianae, while knockdown of its expression increased the resistance. Manipulation of NtbHLH49 expression also altered the expression of a set of pathogen resistance genes. This study identified a set of genes correlated with JA-mediated tobacco response to P. nicotianae, and revealed the function of AtBPE-like regulator NtbHLH49 in regulating tobacco resistance to this pathogen, providing insights into the JA-mediated tobacco responses to P. nicotianae.

Genome Editing Reveals Both the Crucial Role of OsCOI2 in Jasmonate Signaling and the Functional Diversity of COI1 Homologs in Rice.

Jasmonic acid (JA) regulates plant growth, development and stress responses. Coronatine insensitive 1 (COI1) and jasmonate zinc-finger inflorescence meristem-domain (JAZ) proteins form a receptor complex for jasmonoyl-l-isoleucine, a biologically active form of JA. Three COIs (OsCOI1a, OsCOI1b and OsCOI2) are encoded in the rice genome. In the present study, we generated mutants for each rice COI gene using genome editing to reveal the physiological functions of the three rice COIs. The oscoi2 mutants, but not the oscoi1a and oscoi1b mutants, exhibited severely low fertility, indicating the crucial role of OsCOI2 in rice fertility. Transcriptomic analysis revealed that the transcriptional changes after methyl jasmonate (MeJA) treatment were moderate in the leaves of oscoi2 mutants compared to those in the wild type or oscoi1a and oscoi1b mutants. MeJA-induced chlorophyll degradation and accumulation of antimicrobial secondary metabolites were suppressed in oscoi2 mutants. These results indicate that OsCOI2 plays a central role in JA response in rice leaves. In contrast, the assessment of growth inhibition upon exogenous application of JA to seedlings of each mutant revealed that rice COIs are redundantly involved in shoot growth, whereas OsCOI2 plays a primary role in root growth. In addition, a co-immunoprecipitation assay showed that OsJAZ2 and OsJAZ5 containing divergent Jas motifs physically interacted only with OsCOI2, whereas OsJAZ4 with a canonical Jas motif interacts with all three rice COIs. The present study demonstrated the functional diversity of rice COIs, thereby providing clues to the mechanisms regulating the various physiological functions of JA.

ZmRop1 participates in maize defense response to the damage of Spodoptera frugiperda larvae through mediating ROS and soluble phenol production.

As plant-specific molecular switches, Rho-like GTPases (Rops) are vital for plant survival in response to biotic and abiotic stresses. However, their roles in plant defense response to phytophagous insect's damage are largely unknown. In this study, the expression levels of nine maize RAC family genes were analyzed after fall armyworm (FAW) larvae infestation. Among the analyzed genes, ZmRop1 was specifically and highly expressed, and its role in maize response to FAW larvae damage was studied. The results showed that upon FAW larvae infestation, salicylic acid and methyl jasmonate treatment ZmRop1 gene transcripts were all down-regulated. However, upon mechanical injury, the expression level of ZmRop1 was up-regulated. Overexpression of ZmRop1 gene in maize plants could improve maize plant resistance to FAW larvae damage. Conversely, silencing of ZmRop1 increased maize plant susceptibility to FAW larvae damage. The analysis of the potential anti-herbivore metabolites, showed that ZmRop1 promoted the enzyme activities of catalase, peroxidase and the expression levels of ZmCAT, ZmPOD, ZmRBOHA and ZmRBOHB, thereby enhancing the reactive oxygen species (ROS) production, including the content of O2- and H2O2. In addition, overexpression or silencing of ZmRop1 could have influence on the content of the total soluble phenol through mediating the activity of polyphenol oxidase. In summary, the results illuminated our understanding of how ZmRop1 participate in maize defense response to FAW larvae damage as a positive regulator through mediating ROS production and can be used as a reference for the green prevention and control of FAW larvae.

Early warning of Diaporthe infection in kiwifruit soft rot by plasmonic dimer-enhanced Raman spectroscopy.

Diaporthe genus is the dominant pathogens of kiwifruit soft rot with long incubation period and rapid onset and very hard to detect in advance. It is of great significance to develop point-of-care tests for disease prevention and field management. Here we screen a pair of genus-level primers for constructing plasmonic dimer Rayleigh/Raman spectroscopy, which enables rapid, specific, and sensitive detection of Diaporthe genus in real kiwifruits. Dark-filed Rayleigh scattering clearly visualizes the target-induced dimer assembly of nanoprobes. Plasmonic dimer-enhanced Raman spectroscopy has high specificity for 12 common isolates of Diaporthe genus in one batch samples with highly accurate results and much higher sensitivity than polymerase chain reaction (PCR). It realizes the recognition of Diaporthe infection at an early stage of 24h when the kiwifruits do not have any noticeable symptoms. It demonstrates a bright prospect of point-of-care tests for early warning of kiwifruit soft rot infection and quality control.

Postharvest methyl jasmonate treatment inhibits blue mold decay in Ginkgo biloba seeds by inducing antioxidant and defense systems

Postharvest methyl jasmonate treatment inhibits blue mold decay in Ginkgo biloba seeds by inducing antioxidant and defense systems

Genome-Wide Characterization, Identification and Expression Profile of MYB Transcription Factor Gene Family during Abiotic and Biotic Stresses in Mango (Mangifera indica).

Mango (Mangifera indica) is an economically important fruit tree, and is cultivated in tropical, subtropical, and dry-hot valley areas around the world. Mango fruits have high nutritional value, and are mainly consumed fresh and used for commercial purposes. Mango is affected by various environmental factors during its growth and development. The MYB transcription factors participates in various physiological activities of plants, such as phytohormone signal transduction and disease resistance. In this study, 54 MiMYB transcription factors were identified in the mango genome (371.6 Mb). A phylogenetic tree was drawn based on the amino acid sequences of 222 MYB proteins of mango and Arabidopsis. The phylogenetic tree showed that the members of the mango MYB gene family were divided into 7 group, including Groups 1, -3, -4, -5, -6, -8, and -9. Ka/Ks ratios generally indicated that the MiMYBs of mango were affected by negative or positive selection. Quantitative real-time PCR showed that the transcription levels of MiMYBs were different under abiotic and biotic stresses, including salicylic acid, methyl jasmonate, and H2O2 treatments, and Colletotrichum gloeosporioides and Xanthomonas campestris pv. mangiferaeindicae infection, respectively. The transcript levels of MiMYB5, -35, -36, and -54 simultaneously responded positively to early treatments with salicylic acid, methyl jasmonate, and H2O2. The transcript level of MiMYB54 was activated by pathogenic fungal and bacterial infection. These results are beneficial for future interested researchers aiming to understand the biological functions and molecular mechanisms of MiMYB genes.

Overexpression of SmMYC2 enhances salt resistance in Arabidopsis thaliana and Salvia miltiorrhiza hairy roots

Soil salinity significantly affects both Salvia miltiorrhiza growth and development as well as seed germination throughout field cultivation and production. The basic helix-loop-helix (bHLH) transcription factor (TF) MYC2 contributes significantly to plant stress resistance as a key regulator of the jasmonic acid signaling pathway. In transgenic S. miltiorrhiza hairy roots, SmMYC2 has been shown to promote the accumulation of tanshinone and salvianolic acid, but its role in S. miltiorrhiza of resistance to abiotic stress is unclear. Herein, we found methyl jasmonate (MeJA), NaCl, and PEG treatment all significantly increased SmMYC2 expression. In response to salt stress, SmMYC2 overexpression in yeast increased its rate of growth. Additionally, overexpression of SmMYC2 transgenic Arabidopsis thaliana and S. miltiorrhiza hairy root showed that it might improve salt resistance in transgenic plant. In particular, compared to WT, overexpression of SmMYC2 transgenic Arabidopsis had higher levels of three antioxidant enzymes (superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)), proline (Pro) content, and ABA-dependent and ABA-independent genes expression. They also had lower levels of malondialdehyde (MDA) and reactive oxygen species (ROS) accumulation. What's more, overexpression of SmMYC2 increases the expression of flavonoid synthesis genes and the accumulation of related components in Arabidopsis. These findings imply that SmMYC2 functions as a positive regulator that regulates plant tolerance to salt through ABA-dependent and independent signaling pathways.

Genome-wide identification and expression analysis of the TCP genes in Senna tora reveal the regulatory mechanism of their response to MeJA

Teosinte Branched1/Cycloidea/Proliferating cell factor (TCP) genes constitute a unique and small class of transcription factors in plants, and are highly important in hormone response and secondary metabolite accumulation. However, Senna tora L. (S. tora) TCP genes have not been studied. In this study, the whole S. tora TCP genome was analyzed to explore its evolution and function. A protein interaction experiment was conducted to further analyze the involvement of TCP in jasmonic acid (JA) signal transduction. A total of 24 TCP TFs were identified in the S. tora genome, and were divided into 2 classes and 3 subfamilies. We found that 16 StTCP gene pairs with collinearity were distributed on 10 different chromosomes, with only one tandem repeat. The expression profiles at different seed developmental stages and tissue specificity analysis showed that StTCP4.1 and StTCP11 may regulate the synthesis of anthraquinone compounds in S. tora. Gene expression levels determined under methyl jasmonate (MeJA) treatment and gene network correlation analysis showed that StTCP4.1 and StTCP11 may be involved in jasmonic acid (JA) response signaling. In addition, subcellular localization analysis showed that StTCP4.1 and StTCP11 were expressed and elicited their functions in the nucleus. Yeast two-hybrid (Y2H) and luciferase complementation (LCI) assay findings showed that StTCP4.1 could directly interact with StMYC2a. In summary, these findings lay a new foundation for improving understanding on the complex mechanism underlying StTCP function in response to JA-induced signaling pathways and on the regulation of secondary metabolite synthesis in S. tora.

LncRNA4504 involved in methyl jasmonate-induced resistance to Botrytis cinerea in postharvest tomato fruit

• MeJA induced lncRNA4504 expression and tomato fruit resistance to B. cinerea . • The silence of lncRNA4504 aggravated the development of tomato fruit disease . • LncRNA4504 silence counteracted the effects of MeJA on fruit disease resistance. • LncRNA4504 positively regulated MeJA-induced tomato fruit resistance to B.cinerea . Our previous study screened a long non-coding RNA, lncRNA4504, whose expression was largely increased responding to methyl jasmonate (MeJA) treatment in tomato fruit. However, the roles of lncRNA4504 in MeJA-induced fruit resistance remains unclear. Here, lncRNA4504 was silenced using virus-induced gene silencing (VIGS) to investigate its function in MeJA-mediated defense responses to Botrytis cinerea ( B. cinerea ) in tomato fruit. The data showed that tomato fruit treated with MeJA (0.05 mmol L −1 , 12 h) exhibited lower disease symptoms, and higher total phenols and flavonoids contents and defensive enzymes activities, as well as higher transcripts of pathogenesis-related genes ( SlPR1 and SlPR-STH2 ) than control fruit during storage. In addition, MeJA treatment also promoted the transcripts of genes related to jasmonic acid (JA) biosynthesis ( SlLOXD, SlAOS and SlAOC ) and its signal transduction ( SlMYC2 and SlCOI1 ) along with increased endogenous JA content compared to control. However, lncRNA4504 silence almost counteracted the effects of MeJA on the above indexes, leading to higher disease incidence and lesion diameter in (lncRNA4504-silenced + MeJA) group than those in MeJA group. These findings indicated that lncRNA4504 may play vital roles in the tomato disease resistance induced by MeJA, possibly by promoting the accumulation of total phenols and total flavonoids, enhancing defense enzyme activities, and upregulating the expression of JA signal pathway genes.

Changes in Quercetin Derivatives and Antioxidant Activity in Marigold Petals (Tagetes patula L.) Induced by Ultraviolet-B Irradiation and Methyl Jasmonate.

Marigold petals contain numerous antioxidative flavonoids and carotenoids that can be affected by environmental stressors. There is yet no detailed study on the relationship between phytochemical accumulation and stressors in marigold petals. This study evaluated quercetin derivatives and antioxidant activity in marigold petals in response to ultraviolet-B (UV-B) irradiation and methyl jasmonate (MeJA) treatment. The limiting UV-B radiation intensity and MeJA dose that caused no wilting damage under 1-h daily treatment for 10 days were <2 W∙m-2∙s-1 and <10 mM, respectively. Marigold petals contained three major flavonoids, quercetin-7-O-glucoside (Q7G, 6.6 mg∙g-1dw), quercetin-3-O-glucoside (Q3G, 62.7 mg), and quercetin (26.6 mg), possessing different antioxidant potential and exhibiting the highest power in quercetin and next value in Q7G. Single UV-B irradiation exerted a limited effect on the changes in the content of the three quercetin derivatives, whereas combined treatment with 1 W UV-B radiation and 5 mM MeJA resulted in the highest total quercetin content, showing >20% increase compared to that without treatment. This increase primarily resulted in an increase in quercetin content. MeJA treatment positively affected the increase in Q3G and Q7G contents in a dose-dependent manner during the 10-d experimental period but exerted no considerable effect on quercetin accumulation. The antioxidant activity was increased when flowers were exposed to mild MeJA treatment of 5-10 mM. UV-B irradiation decreased the antioxidant activity of marigold petals, but this decrease could be compensated by MeJA treatment.

Weighted Gene Coexpression Network Analysis of Candidate Pathways and Genes in Soft Rot Resistance of Amorphophallus

Amorphophallus species are one of the main economic crops in the mountainous areas of southwest China. However, soft rot disease (Pectobacterium carotovorum ssp. carotovorum) is devastating for this crop. This study explored the Amorphophallus resistance mechanism against soft rot disease by analyzing transcriptome data using a weighted gene coexpression network analysis. The RNA sequencing of plants infected for 0, 12, 24, and 48 hours produced a total of 52.25 Gb of clean reads. A total of 29,096 genes were divided into 34 modules. Six modules of interest with the highest correlation with the target traits were selected to elucidate the resistance genes and pathways. The selected modules were enriched in the α-linolenic acid metabolism, phenylpropane biosynthesis, plant hormone signal transduction, and plant pathogen interaction pathways. Ultimately, AmBGLU, AmCAML, AmCDPK, AmLOX, and AmRBOHD were identified as genes of interest in the four significantly related metabolic pathways for real-time fluorescence quantitative polymerase chain reaction verification. The determination of salicylic acid (SA) and jasmonic acid (JA) in Amorphophallus muelleri and Amorphophallus konjac that suffered from soft rot disease showed that SA and JA were involved in the A. muelleri and A. konjac defense response against soft rot disease. Methyl jasmonate treatment delayed the onset of A. konjac soft rot disease. This study provides a reference for the interaction between Amorphophallus species and soft rot disease and the breeding of broad-spectrum and specific Amorphophallus cultivars that are resistant to soft rot disease.

Pre- or Post-Harvest Treatment with MeJA Improves Post-Harvest Storage of Lemon Fruit by Stimulating the Antioxidant System and Alleviating Chilling Injury.

Cold storage preserves lemon fruit quality; however, it can result in significant chilling injury (CI). The effects of pre- and post-harvest methyl jasmonate (MeJA) treatments at four concentrations (0, 0.1, 0.3, and 0.5 mM) on CI and sensory quality of lemons during 80 d of storage at 7-10 °C were investigated. Both pre- and post-harvest MeJA treatments reduced CI, weight loss (WL) and maintained higher firmness, total soluble solids (TSS), and total acidity (TA) than in the controls. Antioxidant enzyme activities decreased in the control fruit but increased in both pre- and post-harvest MeJA-treated fruit. In addition, phospholipase D (PLD) and lipoxygenase (LOX) activities and malondialdehyde (MDA) content were higher in the control than in the MeJA-treated fruit. Pre-harvest MeJA treatment generally preserved fruit better than post-harvest MeJA treatment, with the best results observed when MeJA was applied at 0.3 mM, which enhanced the antioxidant system of the lemon fruits, thus reducing the post-harvest incidence of chilling injury. These results have important implications for improved fruit quality post-harvest.

The transcription factor VaMYC2 from Chinese wild Vitis amurensis enhances cold tolerance of grape (V. vinifera) by up-regulating VaCBF1 and VaP5CS

Cultivated grapes, one of the most important fruit crops in the world, are sensitive to low temperature. Since Chinese wild grape Vitis amurensis is highly tolerant to cold, it is imperative to study and utilize its cold-tolerance genes for molecular breeding. Here, a VaMYC2 gene from V. amurensis was cloned, and its function was investigated by expressing VaMYC2 in the cold-sensitive V. vinifera cultivar ‘Thompson Seedless’. The expression of VaMYC2 could be induced by cold stress, methyl jasmonate and ethylene treatment, but was inhibited by abscisic acid in leaves of V. amurensis. When transgenic grape lines expressing VaMYC2 were subjected to cold stress (−1 °C) for 41 h, the transgenic lines showed less freezing injury and lower electrolyte leakage and malondialdehyde content, but higher contents of soluble sugars, soluble proteins and proline, and antioxidant enzyme activities compared with wild-type. Moreover, the expression of some cold-tolerance related genes increased in transgenic lines. Besides, the interactions of VaMYC2 with VaJAZ1 and VaJAZ7B were confirmed by yeast two-hybrid and bimolecular fluorescence complementation assays. Yeast one-hybrid and dual luciferase assays showed that VaMYC2 can bind to the promoters of VaCBF1 and VaP5CS and activate their expressions. In conclusion, expression of VaMYC2 in V. vinifera enhances cold tolerance of transgenic grapes which is attributed to enhanced accumulation of osmotic regulatory substances, cell membrane stability, antioxidant enzyme activity, and expression of cold tolerance-related genes. Also, VaMYC2 interacts with VaJAZ1 and VaJAZ7, and activates the expression of VaCBF1 and VaP5CS to mediate cold tolerance in grapes.

The Germin-like protein OsGER4 is involved in promoting crown root development under exogenous jasmonic acid treatment in rice.

In rice (Oryza sativa L.), crown roots (CRs) have many important roles in processes such as root system expansion, water and mineral uptake, and adaptation to environmental stresses. Phytohormones such as auxin, cytokinin, and ethylene are known to control CR initiation and development in rice. However, the role of jasmonic acid (JA) in CR development remained elusive. Here, we report that JA promotes CR development by regulating OsGER4, a rice Germin-like protein. Root phenotyping analysis revealed that exogenous JA treatment induced an increase in CR number in a concentration-dependent manner. A subsequent genome-wide association study and gene expression analyses pinpointed a strong association between the Germin-like protein OsGER4 and the increase in CR number under exogenous JA treatment. The ProGER4::GUS reporter line showed that OsGER4 is a hormone-responsive gene involved in various stress responses, mainly confined to epidermal and vascular tissues during CR primordia development and to vascular bundles of mature crown and lateral roots. Notable changes in OsGER4 expression patterns caused by the polar auxin transport inhibitor NPA support its connection to auxin signaling. Phenotyping experiments with OsGER4 knockout mutants confirmed that this gene is required for CR development under exogenous JA treatment. Overall, our results provide important insights into JA-mediated regulation of CR development in rice.

Functional characterization of a farnesyl diphosphate synthase from Dendrobium nobile Lindl

Dendrobium nobile Lindl. has been used as a traditional Chinese medicine for a long time, in which the most important compound is dendrobine functioning in a variety of pharmacological activities. Farnesyl diphosphate synthase (FPPS) is one of the key enzymes in the biosynthetic pathway of dendrobine. In this work, we found the expression profiles of DnFPPS were correlated with the contents of dendrobine under the methyl jasmonate (MeJA) treatments at different time. Then, the cloning and functional identification of a novel FPPS from D. nobile. The full length of DnFPPS is 1231 bp with an open reading frame of 1047 bp encoding 348 amino acids. The sequence similarity analysis demonstrated that DnFPPS was in the high homology with Dendrobium huoshanense and Dendrobium catenatum and contained four conserved domains. Phylogenetic analysis showed that DnFPPS was the close to the DhFPPS. Then, DnFPPS was induced to express in Escherichia coli, purified, and identified by SDS-PAGE electrophoresis. Gas chromatography-mass spectrometry analysis indicated that DnFPPS could catalyze dimethylallyl pyrophosphate and isopentenyl pyrophosphate to produce farnesyl diphosphate. Taken together, a novel DnFPPS was cloned and functionally identified, which supplied a candidate gene for the biosynthetic pathway of dendrobine.

Dynamic metabolic and transcriptomic profiling reveal synthetic characters and regulators of flavonoid biosynthesis in Camellia oleifera seeds

Flavonoids are natural bioactive substances with beneficial health effects against chronic diseases. Camellia oleifera Abel. ( C. oleifera ) has attracted attention because its seeds contain high levels of unsaturated fatty acids . Actually, flavonoids are also abundant in the C. oleifera seeds. However, the composition and distribution of flavonoid and overall molecular mechanism of flavonoid biosynthesis in the C. oleifera seeds have not been fully uncovered. To this end, metabolome , transcriptome , high-performance liquid chromatography, microscopic, and exogenous methyl jasmonate treatment analyses of C. oleifera seeds at different developmental stages were performed. Results revealed that the differential metabolites and genes were enriched in the flavonoid biosynthesis pathways in C. oleifera seeds. Flavonoid profiles presented dynamic patterns that changed with seed development, consistent with the pattern of gene regulation in the corresponding pathways. In total, 52 differentially accumulated flavonoids and 124 differentially expressed structural genes involved in flavonoid biosynthesis were identified. After weighted gene co-expression network analysis, three modules were highly interrelated with the accumulation of flavonoid components. The co-expression networks of these three modules were used to identify key candidate transcription factors associated with flavonoid biosynthesis, such as MYC2 , bHLH3 , bHLH18 , MYB44 , MYB86 , WRKY26 , and WRKY32 . Based on these differentially accumulated flavonoids and key genes, the genetic and metabolic regulatory networks of flavonoid biosynthesis was proposed. Moreover, exogenous methyl jasmonate influenced the accumulation of diverse flavonoids in C . oleifera seeds. Potential regulatory factors identified in this study will contribute to the provision of molecular traces for in-depth research on flavonoid biosynthesis and product development for C. oleifera with higher value. • In total, 148 flavonoids were identified in Camellia oleifera seeds. • Differentially expressed genes were enriched in the flavonoid biosynthesis pathways. • Seven key transcription factors related to flavonoid biosynthesis were screened. • A model was proposed in which flavonoid biosynthesis is induced by methyl jasmonate.

Hormone-response transcriptional landscapes of wheat seedlings and the development of a JA fluorescent reporter.

Wheat is an essential energy and protein source for humans. Climate change brings daunting challenges to wheat yield through environmental stresses, in which phytohormones play critical roles. Nevertheless, the comprehensive understanding of wheat phytohormone responses remains elusive. Here, we investigated the transcriptome response of wheat seedlings to five phytohormones, cytokinin (6-BA), abscisic acid (ABA), gibberellic acid (GA), jasmonate (JA)and salicylic acid (SA). We further selected two JAmarker genes and cloned their promoters to drive the expression of 3XEGFP (tandem trimeric enhanced green fluorescent protein) in transgenic lines. The JA fluorescent reporter displayed a fast and stable response to JA treatment as an ideal tool to follow JA dynamics during fungal and cold stresses at a cellular resolution. Overall, this study provided a transcriptional landscape and facilitated generating fluorescent reporters to monitor the dynamics of phytohormones in food crops.

Defining key parameters and predictive markers of ‘Early Bigi’ cherry consumer satisfaction by means of differential storage scenarios

To induce differences in sensorial characteristics, ‘Early Bigi’ cherries were exposed to various storage scenarios, including modified atmosphere packaging, 1-methylcyclopropene and methyl jasmonate treatments. Three classes of consumer acceptance (high, medium, and low) were defined and related to changes in standard quality, flavour perception and volatile organic compounds (VOCs) emissions. Consumer satisfaction in ‘Early Bigi’ cherries strongly depended on the acidity levels of the fruit and how the storage scenario modulated this parameter. Multivariate data analysis also revealed a clear relationship between acidity, VOCs emissions and flavour perception that determined fruit acceptance. In this cultivar, flavour perception and consumer satisfaction were also linked to specific volatile compounds. At harvest and during the first 15 d of cold storage, consumer satisfaction was found to mainly depend on high levels of ethyl butanoate, (Z)-3-hexen-1-ol and benzaldehyde and on the other side on low levels of ethyl acetate and ethanol, which were probably perceived as off-flavours or unpleasant compounds. Consumer satisfaction was also related to low levels of 2-methylbutyl butanoate, (Z)-2-hexenyl acetate, linalool and 3-methyl-2-butanol. It is, therefore, possible to envisage the use of these specific volatile compounds as markers for consumer satisfaction in ‘Early Bigi’ cherries and perhaps also in other cherry cultivars.

Postharvest methyl jasmonate treatment enhanced biological activity by promoting phenylpropanoid metabolic pathways in Lilium brownii var. viridulum

Improving the content of bioactive components in horticultural plants, especially edible and medicinal plants, is of great significance for improving horticultural production efficiency. Methyl jasmonate (MeJA) is an important inducer of phytoactive components, but its role in the secondary metabolism of lily is still unclear. In this study, 0, 50, 100 and 200 μmol/L MeJA were used to treat postharvest scales of Lilium brownii var. viridulum. The results showed that exogenous MeJA increased the total phenolic acid content (TPC) and total flavonoid content (TFC) of lily scales several-fold in a short time (72 h), leading to higher antioxidant abilities. qRT–PCR results indicated that MeJA significantly activated the expression of key genes involved in phenylpropanoid metabolism, including phenylalanine ammonia-lyase (PAL), cinnamate-4-hydroxylase (C4H) and 4-coumarate-CoA ligase (4CL), consequently improving their enzyme activities. Consistent with the physiological and gene expression results, metabolome data indicated that multiple metabolic pathways were significantly enhanced by MeJA treatment, including the phenylpropanoid pathway and other downstream metabolic pathways. These results indicated that postharvest treatment with exogenous MeJA promoted the accumulation of secondary metabolites in lily scales by promoting the expression of related genes, which in turn enhanced its nutritional value. The data obtained in this study will not only help to elucidate the regulatory role of MeJA in the secondary metabolism of lily but also provide a low-cost, easy-to-operate, and highly efficient way to enhance the nutrients and medicinal ingredients of horticultural production.