Jasmonates in plant growth and development and elicitation of secondary metabolites: An updated overview

MYB47 delays leaf senescence by modulating jasmonate pathway via direct regulation of CYP94B3/CYP94C1 expression in Arabidopsis

Leaf senescence is a complex genetic process intricately regulated by multiple layers of control. Transcription factors, as master regulators of gene expression, play crucial roles in initiating and progressing leaf senescence. Through screening an activation-tagged mutant library, we identified MYB47 as a negative regulator of leaf senescence. Constitutive or inducible overexpression of MYB47 significantly delays leaf senescence, while loss-of-function mutants exhibit accelerated senescence. Transcriptome analysis revealed a marked suppression of jasmonic acid (JA) signaling in MYB47 overexpression lines. Conversely, the myb47 mutants display elevated JA levels and reduced expression of JA catabolic genes, CYP94B3 and CYP94C1. Biochemical evidence demonstrated that MYB47 directly binds to the promoters of CYP94B3 and CYP94C1, upregulating their expression. Consequently, JA contents are significantly reduced in MYB47 overexpression lines. Overexpressing CYP94B3 or CYP94C1 in myb47 mutants alleviates their early senescence phenotype. Furthermore, JA induces MYB47 expression, forming a negative feedback loop (JA-MYB47-CYP94B3/C1-JA) that fine-tunes leaf senescence. Our findings reveal a novel regulatory module involving MYB47 and JA signaling that governs leaf senescence. By stimulating JA catabolism and attenuating JA signaling, MYB47 plays a crucial role in delaying leaf senescence.

Transcriptome analysis of Thevetia peruviana cell suspensions treated with methyl jasmonate reveals genes involved in phenolics, flavonoids and cardiac glycosides biosynthesis

Thevetia peruviana (Pers.) K. Schum is a tropical shrub with recognized ethnomedicinal applications associated with the presence of secondary metabolites (SMs), which exhibit cardiotonic, antioxidant, antimicrobial and anticancer activities. Previous studies have shown that methyl jasmonate (MeJA), when exogenously applied to T. peruviana cell cultures, activates the production of phenolic compounds (PCs), flavonoids (Fvs) and cardiac glycosides (CGs); however, the biochemical mechanisms involved in the MeJA-regulated biosynthetic pathways remain unknown. To deepen our understanding of the effect of MeJA on the secondary metabolism of T. peruviana, transcriptome sequencing was performed on suspension cell culture. A first draft transcriptome of T. peruviana was obtained, with an average N50 length of 3570 bp, comprising a total of 83126 unigenes. Differential gene expression analysis was conducted to evaluate the effects of treatment with 3 µM MeJA. In MeJA-treated cells, genes involved in the glycolytic pathway were upregulated, providing the necessary energy and metabolic precursors for SMs biosynthesis. Additionally, key genes in the biosynthesis of PCs (HST, ALDH2C4), Fvs (SHT, FLS/F3H, FaGT6) and CGs (ISPF, TPS, SQS1, IPP2, CYP710A3, SCL14, DWF1) were significantly upregulated in response to MeJA. Other notable effects of MeJA included the regulation of transcription factors (bHLH, MYB, bZIP, WRKY and ERF), which are involved in the biosynthesis of target metabolites. This de novo assembly of T. peruviana transcriptome provides a valuable resource for future research in functional genomics and metabolic engineering of bioactive SMs. Additionally, it offers new insights into the molecular mechanisms underlying the plant's response to MeJA, paving the way for targeted strategies to enhance the production of pharmacologically relevant compounds.

PnOPR6 from Antarctic moss mediates JA-ABA crosstalk and enhances abiotic stress tolerance in Arabidopsis

Jasmonates (JAs) and abscisic acid (ABA) are vital plant hormones that are integral to the plant's response mechanisms against various abiotic stresses. These hormones also function in an antagonistic manner to regulate seed germination and dormancy. However, little is known about the molecular mechanism underlying the interaction between ABA and JA signaling. Here, seven 12-oxo-phytodienoic acid reductase genes (PnOPR1-7), a key enzyme in the JA biosynthesis pathway, were identified in the Antarctic moss Pohlia nutans transcriptome, and their expressions in response to abiotic stress were examined. Among these, PnOPR6 expression levels rose most under cold and UV-B stresses. Transgenic Arabidopsis overexpressing PnOPR6 demonstrated increased tolerance to salt, cold, dehydration, glucose, and ABA, but also greater sensitivity to methyl jasmonate (MeJA) during seed germination or early root growth. Furthermore, in the transgenic Arabidopsis, PnOPR6 suppressed the expression of genes involved in the ABA pathway and ABI3/5-responsive JA receptor COI1. Additionally, phytohormone metabolomics investigations revealed a significant rise in JA precursor (OPDA, OPC-6, and OPC-4), JA, and its derivative 12-OH-JA in PnOPR6-overexpressing line. Moreover, the accumulation of flavonoid in Arabidopsis was enhanced by heterologous expression of PnOPR6. These findings imply that PnOPR6 functions as a signaling regulator, improving plant resistance to abiotic stress through flavonoid accumulation and JA-ABA antagonistic crosstalk, therefore aiding P. nutans in adjusting to polar climates.

Molecular mechanisms of high tiller development based on transcriptome and proteome correlation analysis in Poa pratensis

Poa pratensis, a high-quality forage and turfgrass, plays a significant role in grassland construction, biodiversity maintenance, and ecological restoration, and has considerable ecological value. Exploring the molecular mechanisms of high tillering occurrence in Kentucky bluegrass is an effective approach for understanding nutrient dense germplasm materials. Additionally, it provides a theoretical foundation for enhancements in plant yield and competitive survival. In this study, statistical analyses of tiller number and tiller node diameter in two wild Kentucky bluegrass germplasms from Gansu Province were conducted. Transcriptome and proteomic analyses were performed on the tillering nodes of these grasses at various tillering stages, aiming to identify the genes, proteins, and pathways that regulate tillering formation. The 'SN' variety was found to possess stronger tillering abilities and greater tillering potential. Through RNA sequencing (RNA-Seq) and DIA quantitative proteomics, a total of 331,749 Unigenes and 21,140 proteins were identified. Among these, 29,932 Unigenes exhibited differential expression and 6974 proteins demonstrated differential accumulation between the tillering nodes of the two varieties of Kentucky bluegrass. KEGG analysis indicated that differentially expressed genes and proteins were significantly enriched in pathways such as phenylpropanoid biosynthesis, plant hormone signal transduction, glutathione metabolism, starch and sucrose metabolism, as well as secondary metabolite biosynthesis. Joint transcriptome and proteome analysis identified 784, 733, and 483 genes/proteins that were coordinately expressed between the 'SN' and 'QS' varieties at the prophase, peak, and anaphase stages of tillering, respectively. KEGG analysis was conducted on these genes and proteins, revealing that pathways such as phenylpropanoid biosynthesis, glutathione metabolism, and photosynthesis were likely involved in regulating the growth and development of tillers. This study elucidated the biological and metabolic characteristics of Kentucky bluegrass at different tillering stages, aiding in the identification of genes and proteins associated with tillering formation. This work establishes a theoretical foundation for exploring the mechanisms of tillering formation in Kentucky bluegrass.

Metabolomic approaches suggest two mechanisms of drought response post-anthesis in Mediterranean oat (Avena sativa L.) cultivars

Oats (Avena sativa L) is a temperate cereal and an important healthy cereal cultivated for food and feed. Therefore, understanding drought responses in oats could significantly impact oat production under harsh climatic conditions. In particular, drought during anthesis (flowering) affects grain filling, quality and yield. Here, we characterised metabolite responses of two Mediterranean oat (Avena sativa L.) cultivars, Flega and Patones, during drought stress at anthesis. In the more drought-tolerant Patones, the developing grains from the top (older) and bottom (younger) spikelets of primary panicle were found to be larger in size in response to drought, suggesting accelerated grain development. Flega showed a more rapid transition to flowering and grain development under drought. The metabolomes of source (sheath, flag leaf, rachis) and sink (developing grains) tissues from Patones showed differential accumulation in fatty acids levels, including α-linolenic acid, sugars and amino acids with drought. Flega showed enhanced energy metabolism in both source and sink tissues. Lower levels of glutathione in source tissues and the accumulation of ophthalmic acid in the grains of Flega were indicators of oxidative stress. Our study revealed two distinct metabolite regulatory patterns in these cultivars during drought at anthesis. In Patones, α-linolenic acid-associated processes may accelerate grain-filling, while in Flega oxidative stress appears to influence traits such as flowering time. Overall, this work provides a first insight into the metabolite regulation in oat's source and sink tissues during anthesis under drought stress.

Transcriptomic Analysis of the Combined Effects of Methyl Jasmonate and Wounding on Flavonoid and Anthraquinone Biosynthesis in Senna tora

Jasmonates, including jasmonic acid (JA) and its derivatives such as methyl jasmonate (MeJA) or jasmonly isoleucine (JA-Ile), regulate plant responses to various biotic and abiotic stresses. In this study, we applied exogenous MeJA onto Senna tora leaves subjected to wounding and conducted a transcriptome deep sequencing analysis at 1 (T1), 3 (T3), 6 (T6), and 24 (T24) h after MeJA induction, along with the pretreatment control at 0 h (T0). Out of 18,883 mapped genes, we identified 10,048 differentially expressed genes (DEGs) between the T0 time point and at least one of the four treatment times. We detected the most DEGs at T3, followed by T6, T1, and T24. We observed the upregulation of genes related to JA biosynthesis upon exogenous MeJA application. Similarly, transcript levels of genes related to flavonoid biosynthesis increased after MeJA application and tended to reach their maximum at T6. In agreement, the flavonols kaempferol and quercetin reached their highest accumulation at T24, whereas the levels of the anthraquinones aloe-emodin, emodin, and citreorosein remained constant until T24. This study highlights an increase in flavonoid biosynthesis following both MeJA application and mechanical wounding, whereas no significant influence is observed on anthraquinone biosynthesis. These results provide insights into the distinct regulatory pathways of flavonoid and anthraquinone biosynthesis in response to MeJA and mechanical wounding.

Contrast Relative Humidity Response of Diverse Cowpea (Vigna unguiculata (L.) Walp.) Genotypes: Deep Study Using RNAseq Approach

Cowpea (Vigna unguiculata (L.) Walp.) is appreciated for its suitability for cultivation and obtaining good yields in relatively extreme farming conditions. It is resistant to high temperatures and drought. Moreover, food products prepared from Vigna are rich in many nutrients such as proteins, amino acids, carbohydrates, minerals, fiber, vitamins, and other bioactive compounds. However, in East and Southeast Asia, where the products of this crop are in demand, the climate is characterized by excessive humidity. Under these conditions, the vast majority of cowpea varieties tend to have indeterminate growth (elongated shoot length) and are unsuitable for mechanized harvesting. The molecular mechanisms for tolerance to high relative humidity remain the least studied in comparison with those for other abiotic stress factors (drought, heat, cold, flooding, etc.). The purpose of the work was to reveal and investigate differentially expressed genes in cowpea accessions having contrasting growth habits (determinate and indeterminate) under humid and drought conditions. We performed RNA-seq analysis using selected cowpea accessions from the VIR collection. Among the genotypes used, some have significant changes in their plant architecture in response to high relative humidity, while others were tolerant to these conditions. In total, we detected 1697 upregulated and 1933 downregulated genes. The results showed that phytohormone-related genes are involved in cowpea response to high relative humidity. DEGs associated with jasmonic acid signaling are proposed to be key contributors in the maintenance of compact architecture under humid conditions.

Applicability of metabolomics to improve sustainable grapevine production

Metabolites represent the end product of gene expression, protein interaction and other regulatory mechanisms. The metabolome reflects a biological system's response to genetic and environmental changes, providing a more accurate description of plants' phenotype than the transcriptome or the proteome. Grapevine (Vitis vinifera L.), established for the production of wine grapes, table grapes, and raisins, holds immense agronomical and economic significance not only in the Mediterranean region but worldwide. As all plants, grapevines face the adverse impact of biotic and abiotic stresses that negatively affect multiple stages of grape and wine industry, including plant and berry development pre- and post-harvest, fresh grapes processing and consequently wine quality. In the present review we highlight the applicability of metabolome analysis in the understanding of the mechanisms involved in grapevine response and acclimatization upon the main biotic and abiotic constrains. The metabolome of induced morphogenic processes such as adventitious rooting and somatic embryogenesis is also explored, as it adds knowledge on the physiological and molecular phenomena occurring in the explants used, and on the successfully propagation of grapevines with desired traits. Finally, the microbiome-induced metabolites in grapevine are discussed in view of beneficial applications derived from the plant symbioses.

The OsMYC2-JA feedback loop regulates diurnal flower-opening time via cell wall loosening in rice

Diurnal flower-opening time (DFOT), the time of spikelet opening during the day, is an important trait for hybrid rice (Oryza sativa L.) seed production. Hybrids between indica and japonica rice varieties have strong heterosis, but the parental lines usually have different, nonoverlapping DFOTs. This reduces the success of hybrid seed production in crosses between indica and japonica subspecies, thus hindering the utilization of indica and japonica inter-subspecies heterosis. However, little is known about the molecular mechanisms regulating DFOT in rice. Here, we obtained japonica rice lines with a DFOT 1.5 h earlier than the wild type by overexpressing OsMYC2, a gene encoding a key transcription factor in the jasmonate (JA) signaling pathway. OsMYC2 is activated by JA signaling and directly regulates the transcription of genes related to JA biosynthesis and cell wall metabolism. Overexpressing OsMYC2 led to significantly increased JA contents and decreased cellulose and hemicellulose contents in lodicule cells, as well as the softening of lodicule cell walls. This may facilitate the swelling of lodicules, resulting in early diurnal flower-opening. These results suggest that the OsMYC2-JA feedback loop regulates DFOT in rice via cell wall remodeling. These findings shed light on the understanding of regulatory mechanism of the DFOT of plants, which should promote the development of indica and japonica varieties suitable for hybrid rice breeding.

Genome-wide identification of Ankyrin (ANK) repeat gene families in three Dendrobium species and the expression of ANK genes in D. officinale under gibberellin and abscisic acid treatments

BACKGROUND

Dendrobium Sw. represents one of the most expansive genera within the Orchidaceae family, renowned for its species' high medicinal and ornamental value. In higher plants, the ankyrin (ANK) repeat protein family is characterized by a unique ANK repeat domain, integral to a plethora of biological functions and biochemical activities. The ANK gene family plays a pivotal role in various plant physiological processes, including stress responses, hormone signaling, and growth. Hence, investigating the ANK gene family and identifying disease-resistance genes in Dendrobium is of paramount importance.

RESULTS

This research identified 78 ANK genes in Dendrobium officinale Kimura et Migo, 77 in Dendrobium nobile Lindl., and 58 in Dendrobium chrysotoxum Lindl. Subsequently, we conducted comprehensive bioinformatics analyses on these ANK gene families, encompassing gene classification, chromosomal localization, phylogenetic relationships, gene structure and motif characterization, cis-acting regulatory element identification, collinearity assessment, protein-protein interaction network construction, and gene expression profiling. Concurrently, three DoANK genes (DoANK14, DoANK19, and DoANK47) in D. officinale were discerned to indirectly activate the NPR1 transcription factor in the ETI system via SA, thereby modulating the expression of the antibacterial PR gene. Hormonal treatments with GA3 and ABA revealed that 17 and 8 genes were significantly up-regulated, while 4 and 8 genes were significantly down-regulated, respectively. DoANK32 was found to localize to the ArfGAP gene in the endocytosis pathway, impacting vesicle transport and the polar movement of auxin.

CONCLUSION

Our findings provide a robust framework for the taxonomic classification, evolutionary analysis, and functional prediction of Dendrobium ANK genes. The three highlighted ANK genes (DoANK14, DoANK19, and DoANK47) from D. officinale may prove valuable in disease resistance and stress response research. DoANK32 is implicated in the morphogenesis and development of D. officinale through its role in vesicular transport and auxin polarity, with subcellular localization studies confirming its presence in the nucleus and cell membrane. ANK genes displaying significant expression changes in response to hormonal treatments could play a crucial role in the hormonal response of D. officinale, potentially inhibiting its growth and development through the modulation of plant hormones such as GA3 and ABA.

MeJA-induced hairy roots in Plumbago auriculata L. by RNA-seq profiling and key synthase provided new insights into the sustainable production of plumbagin and saponins

Naturally synthesized secondary metabolites in plants are considered an important source of drugs, food additives, etc. Among them, research on natural plant medicinal components and their synthesis mechanisms has always been of high concern. We identified a novel medicinal floral crop, Plumbago auriculata L., that can be treated with methyl jasmonate (MeJA) for the rapid or sustainable production of natural bioactives from hairy roots. In the study, we globally analyzed the changes in the accumulation of plumbagin and others in the hairy roots of Plumbago auriculata L. hairy roots (PAHR) 15834 in P. auriculata L. based on 100 μmol/L of MeJA treatment by RNA-seq profiling, and we found that there was a significant increase in the accumulation of plumbagin and saponin before 24 h. To explain the principle of co-accumulation, it showed that MeJA induced JA signaling and the shikimic acid pathway, and the methylvaleric acid (MVA) pathway was activated downstream subsequently by the Mfuzz and weighted gene co-expression analysis. Under the shared metabolic pathway, the high expression of PAL3 and HMGR promoted the activity of the "gateway enzymes" phenylalanine ammonia lyase (PAL) and 3-hydroxy-3-methylglutaryl CoA reductase (HMGR), which respectively induced the high expression of key reaction enzyme genes, including chalcone synthase (CHS), isopentenyl diphosphate (IPP), and farnesyl pyrophosphate synthase (FPS), that led to the synthesis of plumbagin and saponin. We speculated that large amounts of ketones and/or aldehydes were formed under the action of these characteristic enzymes, ultimately achieving their co-accumulation through polyketone and high-level sugar and amino acid metabolism. The study results provided a theoretical basis for carrying out the factory refinement and biosynthesis of plumbagin and saponins and also provided new ideas for fully exploiting multifunctional agricultural crops and plants and developing new agricultural by-products.

A signaling cascade mediating fruit trait development via phosphorylation-modulated nuclear accumulation of JAZ repressor

It is generally accepted that jasmonate-ZIM domain (JAZ) repressors act to mediate jasmonate (JA) signaling via CORONATINE-INSENSITIVE1 (COI1)-mediated degradation. Here, we report a cryptic signaling cascade where a JAZ repressor, FvJAZ12, mediates multiple signaling inputs via phosphorylation-modulated subcellular translocation rather than the COI1-mediated degradation mechanism in strawberry (Fragaria vesca). FvJAZ12 acts to regulate flavor metabolism and defense response, and was found to be the target of FvMPK6, a mitogen-activated protein kinase that is capable of responding to multiple signal stimuli. FvMPK6 phosphorylates FvJAZ12 at the amino acid residues S179 and T183 adjacent to the PY residues, thereby attenuating its nuclear accumulation and relieving its repression for FvMYC2, which acts to control the expression of lipoxygenase 3 (FvLOX3), an important gene involved in JA biosynthesis and a diverse array of cellular metabolisms. Our data reveal a previously unreported mechanism for JA signaling and decipher a signaling cascade that links multiple signaling inputs with fruit trait development.

Integrated metabolomic and metagenomic strategies shed light on interactions among planting environments, rhizosphere microbiota, and metabolites of tobacco in Yunnan, China

Changes in climatic factors and rhizosphere microbiota led plants to adjust their metabolic strategies for survival under adverse environmental conditions. Changes in plant metabolites can mediate crop growth and development and interact with rhizosphere microbiota of the plant rhizosphere. To understand the interactions among environmental factors, rhizosphere microbiota, and metabolites of tobacco, a study was conducted by using integrated metagenomic and metabolomic strategies at four typical representative tobacco planting sites in Yunnan, China. The results showed that the agronomical and biochemical traits were significantly affected by temperature, precipitation (PREP), soil pH, and altitude. Correlation analyses revealed a significant positive correlation of temperature with length, width, and area of the leaf, while PREP correlated with plant height and effective leaf numbers. Furthermore, total sugar and reducing sugar contents of baked leaves were significantly higher, while the total nitrogen and total alkaloid levels were lower in tobacco leaves at site with low PREP. A total of 770 metabolites were detected with the highest number of different abundant metabolites (DMs) at Chuxiong (CX) with low PREP as compared to the other three sites, in which secondary metabolites were more abundant in both leaves and roots of tobacco. A total of 8,479 species, belonging to 2,094 genera with 420 individual bins (including 13 higher-quality bins) harboring 851,209 CDSs were detected. The phyla levels of microorganisms such as Euryarchaeota, Myxococcota, and Deinococcota were significantly enriched at the CX site, while Pseudomonadota was enriched at the high-temperature site with good PREP. The correlation analyses showed that the metabolic compounds in low-PREP site samples were positively correlated with Diaminobutyricimonas, Nissabacter, Alloactinosynnema, and Catellatospora and negatively correlated with Amniculibacterium, Nordella, Noviherbaspirillum, and Limnobacter, suggesting that the recruitment of Diaminobutyricimonas, Nissabacter, Alloactinosynnema, and Catellatospora in the rhizosphere induces the production and accumulation of secondary metabolites (SMs) (e.g., nitrogen compounds, terpenoids, and phenolics) for increasing drought tolerance with an unknown mechanism. The results of this study may promote the production and application of microbial fertilizers and agents such as Diaminobutyricimonas and Alloactinosynnema to assemble synthetic microbiota community or using their gene resources for better cultivation of tobacco as well as other crops in drought environments.

Genome Mining of a Fungal Polyketide Synthase-Nonribosomal Peptide Synthetase Hybrid Megasynthetase Pathway to Synthesize a Phytotoxic N-Acyl Amino Acid

Guided by the retrobiosynthesis hypothesis, we characterized a fungal polyketide synthase-nonribosomal peptide synthetase (PKS-NRPS) hybrid megasynthetase pathway to generate 2-trans-4-trans-2-methylsorbyl-d-leucine (1), a polyketide amino acid conjugate that inhibits Arabidopsis root growth. The biosynthesis of 1 includes a PKS-NRPS enzyme to assemble an N-acyl amino alcohol intermediate, which is further oxidized to an N-acyl amino acid (NAAA), demonstrating a new biosynthetic logic for synthesizing NAAAs and expanding the chemical space of products encoded by fungal PKS-NRPS clusters.

Strategies, Achievements, and Potential Challenges of Plant and Microbial Chassis in the Biosynthesis of Plant Secondary Metabolites

Diverse secondary metabolites in plants, with their rich biological activities, have long been important sources for human medicine, food additives, pesticides, etc. However, the large-scale cultivation of host plants consumes land resources and is susceptible to pest and disease problems. Additionally, the multi-step and demanding nature of chemical synthesis adds to production costs, limiting their widespread application. In vitro cultivation and the metabolic engineering of plants have significantly enhanced the synthesis of secondary metabolites with successful industrial production cases. As synthetic biology advances, more research is focusing on heterologous synthesis using microorganisms. This review provides a comprehensive comparison between these two chassis, evaluating their performance in the synthesis of various types of secondary metabolites from the perspectives of yield and strategies. It also discusses the challenges they face and offers insights into future efforts and directions.

Identification of transcription factor genes responsive to MeJA and characterization of a LaMYC2 transcription factor positively regulates lycorine biosynthesis in Lycoris aurea

Jasmonates (JAs) are among the main phytohormones, regulating plant growth and development, stress responses, and secondary metabolism. As the major regulator of the JA signaling pathway, MYC2 also plays an important role in plant secondary metabolite synthesis and accumulation. In this study, we performed a comparative transcriptome analysis of Lycoris aurea seedlings subjected to methyl jasmonate (MeJA) at different treatment times. A total of 31,193 differentially expressed genes (DEGs) were identified by RNA sequencing. Among them, 732 differentially expressed transcription factors (TFs) comprising 51 TF families were characterized. The most abundant TF family was WRKY proteins (80), followed by AP2/ERF-EFR (67), MYB (59), bHLH (52), and NAC protein (49) families. Subsequently, by calculating the Pearson's correlation coefficient (PCC) between the expression level of TF DEGs and the lycorine contents, 41 potential TF genes (|PCC| >0.8) involved in lycorine accumulation were identified, including 36 positive regulators and 5 negative regulators. Moreover, a MeJA-inducible MYC2 gene (namely LaMYC2) was cloned on the basis of transcriptome sequencing. Bioinformatic analyses revealed that LaMYC2 proteins contain the bHLH-MYC_N domain and bHLH-AtAIB_like motif. LaMYC2 protein is localized in the cell nucleus, and can partly rescue the MYC2 mutant in Arabidopsis thaliana. LaMYC2 protein could interact with most LaJAZs (especially LaJAZ3 and LaJAZ4) identified previously. Transient overexpression of LaMYC2 increased lycorine contents in L. aurea petals, which might be associated with the activation of the transcript levels of tyrosine decarboxylase (TYDC) and phenylalanine ammonia lyase (PAL) genes. By isolating the 887-bp-length promoter fragment upstream of the start codon (ATG) of LaTYDC, we found several different types of E-box motifs (CANNTG) in the promoter of LaTYDC. Further study demonstrated that LaMYC2 was indeed able to bind the E-box (CACATG) present in the LaTYDC promoter, verifying that the pathway genes involved in lycorine biosynthesis could be regulated by LaMYC2, and that LaMYC2 has positive roles in the regulation of lycorine biosynthesis. These findings demonstrate that LaMYC2 is a positive regulator of lycorine biosynthesis and may facilitate further functional research of the LaMYC2 gene, especially its potential regulatory roles in Amaryllidaceae alkaloid accumulation in L. aurea.

Effect of Mechanical Damage in Green-Making Process on Aroma of Rougui Tea

Rougui Tea (RGT) is a typical Wuyi Rock Tea (WRT) that is favored by consumers for its rich taste and varied aroma. The aroma of RGT is greatly affected by the process of green-making, but its mechanism is not clear. Therefore, in this study, fresh leaves of RGT in spring were picked, and green-making (including shaking and spreading) and spreading (unshaken) were, respectively, applied after sun withering. Then, they were analyzed by GC-TOF-MS, which showed that the abundance of volatile compounds with flowery and fruity aromas, such as nerolidol, jasmine lactone, jasmone, indole, hexyl hexanoate, (E)-3-hexenyl butyrate and 1-hexyl acetate, in green-making leaves, was significantly higher than that in spreading leaves. Transcriptomic and proteomic studies showed that long-term mechanical injury and dehydration could activate the upregulated expression of genes related to the formation pathways of the aroma, but the regulation of protein expression was not completely consistent. Mechanical injury in the process of green-making was more conducive to the positive regulation of the allene oxide synthase (AOS) branch of the α-linolenic acid metabolism pathway, followed by the mevalonate (MVA) pathway of terpenoid backbone biosynthesis, thus promoting the synthesis of jasmonic acid derivatives and sesquiterpene products. Protein interaction analysis revealed that the key proteins of the synthesis pathway of jasmonic acid derivatives were acyl-CoA oxidase (ACX), enoyl-CoA hydratase (MFP2), OPC-8:0 CoA ligase 1 (OPCL1) and so on. This study provides a theoretical basis for the further explanation of the formation mechanism of the aroma substances in WRT during the manufacturing process.

Methyl-Jasmonate Functions as a Molecular Switch Promoting Cross-Talk between Pathways for the Biosynthesis of Isoprenoid Backbones Used to Modify Proteins in Plants

In plants, the plastidial mevalonate (MVA)-independent pathway is required for the modification with geranylgeranyl groups of CaaL-motif proteins, which are substrates of protein geranylgeranyltransferase type-I (PGGT-I). As a consequence, fosmidomycin, a specific inhibitor of 1-deoxy-d-xylulose (DX)-5 phosphate reductoisomerase/DXR, the second enzyme in this so-called methylerythritol phosphate (MEP) pathway, also acts as an effective inhibitor of protein prenylation. This can be visualized in plant cells by confocal microscopy by expressing GFP-CaM-CVIL, a prenylation sensor protein. After treatment with fosmidomycin, the plasma membrane localization of this GFP-based sensor is altered, and a nuclear distribution of fluorescence is observed instead. In tobacco cells, a visual screen of conditions allowing membrane localization in the presence of fosmidomycin identified jasmonic acid methyl esther (MeJA) as a chemical capable of gradually overcoming inhibition. Using Arabidopsis protein prenyltransferase loss-of-function mutant lines expressing GFP-CaM-CVIL proteins, we demonstrated that in the presence of MeJA, protein farnesyltransferase (PFT) can modify the GFP-CaM-CVIL sensor, a substrate the enzyme does not recognize under standard conditions. Similar to MeJA, farnesol and MVA also alter the protein substrate specificity of PFT, whereas DX and geranylgeraniol have limited or no effect. Our data suggest that MeJA adjusts the protein substrate specificity of PFT by promoting a metabolic cross-talk directing the origin of the prenyl group used to modify the protein. MVA, or an MVA-derived metabolite, appears to be a key metabolic intermediate for this change in substrate specificity.

Transcriptome Analysis of White- and Red-Fleshed Apple Fruits Uncovered Novel Genes Related to the Regulation of Anthocyanin Biosynthesis

The red flesh coloration of apples is a result of a biochemical pathway involved in the biosynthesis of anthocyanins and anthocyanidins. Based on apple genome analysis, a high number of regulatory genes, mainly transcription factors such as MYB, which are components of regulatory complex MYB-bHLH-WD40, and several structural genes (PAL, 4CL, CHS, CHI, F3H, DFR, ANS, UFGT) involved in anthocyanin biosynthesis, have been identified. In this study, we investigated novel genes related to the red-flesh apple phenotype. These genes could be deemed molecular markers for the early selection of new apple cultivars. Based on a comparative transcriptome analysis of apples with different fruit-flesh coloration, we successfully identified and characterized ten potential genes from the plant hormone transduction pathway of auxin (GH3); cytokinins (B-ARR); gibberellins (DELLA); abscisic acid (SnRK2 and ABF); brassinosteroids (BRI1, BZR1 and TCH4); jasmonic acid (MYC2); and salicylic acid (NPR1). An analysis of expression profiles was performed in immature and ripe fruits of red-fleshed cultivars. We have uncovered genes mediating the regulation of abscisic acid, salicylic acid, cytokinin, and jasmonic acid signaling and described their role in anthocyanin biosynthesis, accumulation, and degradation. The presented results underline the relationship between genes from the hormone signal transduction pathway and UFGT genes, which are directly responsible for anthocyanin color transformation as well as anthocyanin accumulation during apple-fruit ripening.

Exogenous methyl jasmonate affects genes involved in monoterpene biosynthetic pathway, phyto-biochemical accumulation, and enzymatic activity of Satureja hortensis L

Satureja hortensis L. (SH) is a medicinal and aromatic herb utilized markedly in the food, pharmaceutical, and cosmetic industries because of its specific secondary metabolites (SMs), especially monoterpenoids. However, the impact of elicitors on the expression of monoterpene synthase genes in SH remains unexplored. Therefore, the supreme objective of this research was to elucidate the phyto-biochemical and targeted genes expression responses of SH to the exogenous application of methyl jasmonate (MeJA). Accordingly, having chosen four concentrations of MeJA, they sprayed at the five-leaf stage for two weeks, and then leaves were harvested at two exposure times of 24 and 48 hrs for further analysis, using spectrophotometric, real time-quantitative polymerase chain reaction (RT-qPCR), and gas chromatography-mass spectrometric (GC-MS) methods. The results highlight that not only were the highest contents of phenolic, flavonoids, peroxidase, superoxide dismutase, proline, and malondialdehyde in the elicited SHs but also the highest expression of β-farnesene synthase (BFS) and 1-deoxy-D-xylulose 5-phosphate reductase (DXR) genes together with the highest amount of carvacrol were up-regulated in them compared to their respective control. In conclusion, these findings demonstrate the great industrial potential of MeJA in improving the production of phytochemicals in medicinal plants, particularly in SH.

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 10 µM JA and 10 µM BR in both single and combination forms on bamboo plants grown under Pb stress (0, 50, 100, 150 µM) with a completely randomized design by four replications. The study found that applying 10 µM JA and 10 µM 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 10 µM dose may have the potential to yield optimal efficiency in mitigating oxidative stress in bamboo plants.

An integrated metabolomic and transcriptomic analysis reveals the dynamic changes of key metabolites and flavor formation over Tieguanyin oolong tea production

To interpret the formation characteristic flavor during oolong tea manufacturing process, the dynamic changes of key flavor components in samples from various processing steps of Tieguanyin oolong tea production were investigated using widely-targeted metabolomic and the transcriptomic approaches. As a result, a total of 1078 metabolites were determined, of which 62 compounds were identified as biomarkers significantly changed over the manufacturing process. Quantitative determination of the total 50,343 transcripts showed 7480 of them were co-expressed different genes. Glutamic acid served as a critical metabolism hub and a signaling molecule for diverse stress responses. Additionally, the targeted quantification results showed that the contents of catechins and xanthine alkaloids in dried tea were dramatically decreased by 20.19% and 7.15% respectively than those in fresh leaves, which potentially contributed to the alleviation of astringent or bitter palates, promoting the characteristic mellow and rich flavor of Tieguanyin oolong tea.

Integrating transcriptome and metabolome to explore the growth-promoting mechanisms of GABA in blueberry plantlets

Tissue culture technology is the main method for the commercial propagation of blueberry plants, but blueberry plantlets grow slowly and have long growth cycles under in vitro propagation, resulting in low propagation efficiency. In addition, the long culturing time can also result in reduced nutrient content in the culture medium, and the accumulation of toxic and harmful substances that can lead to weak growth for the plantlets or browning and vitrification, which ultimately can seriously reduce the quality of the plantlets. Gamma-aminobutyric acid (GABA) is a four-carbon non-protein amino acid that can improve plant resistance to various stresses and promote plant growth, but the effects of its application and mechanism in tissue culture are still unclear. In this study, the effects of GABA on the growth of in vitro blueberry plantlets were analyzed following the treatment of the plantlets with GABA. In addition, the GABA-treated plantlets were also subjected to a comparative transcriptomic and metabolomic analysis. The exogenous application of GABA significantly promoted growth and improved the quality of the blueberry plantlets. In total, 2,626 differentially expressed genes (DEGs) and 377 differentially accumulated metabolites (DAMs) were detected by comparison of the control and GABA-treated plantlets. Most of the DEGs and DAMs were involved in carbohydrate metabolism and biosynthesis of secondary metabolites. The comprehensive analysis results indicated that GABA may promote the growth of blueberry plantlets by promoting carbon metabolism and nitrogen assimilation, as well as increasing the accumulation of secondary metabolites such as flavonoids, steroids and terpenes.

The advent of plant cells in bioreactors

Ever since agriculture started, plants have been bred to obtain better yields, better fruits, or sustainable products under uncertain biotic and abiotic conditions. However, a new way to obtain products from plant cells emerged with the development of recombinant DNA technologies. This led to the possibility of producing exogenous molecules in plants. Furthermore, plant chemodiversity has been the main source of pharmacological molecules, opening a field of plant biotechnology directed to produce high quality plant metabolites. The need for different products by the pharma, cosmetics agriculture and food industry has pushed again to develop new procedures. These include cell production in bioreactors. While plant tissue and cell culture are an established technology, beginning over a hundred years ago, plant cell cultures have shown little impact in biotechnology projects, compared to bacterial, yeasts or animal cells. In this review we address the different types of bioreactors that are currently used for plant cell production and their usage for quality biomolecule production. We make an overview of Nicotiana tabacum, Nicotiana benthamiana, Oryza sativa, Daucus carota, Vitis vinifera and Physcomitrium patens as well-established models for plant cell culture, and some species used to obtain important metabolites, with an insight into the type of bioreactor and production protocols.

Important Factors Controlling Gibberellin Homeostasis in Plant Height Regulation

Plant height is an important agronomic trait that is closely associated with crop yield and quality. Gibberellins (GAs), a class of highly efficient plant growth regulators, play key roles in regulating plant height. Increasing reports indicate that transcriptional regulation is a major point of regulation of the GA pathways. Although substantial knowledge has been gained regarding GA biosynthetic and signaling pathways, important factors contributing to the regulatory mechanisms homeostatically controlling GA levels remain to be elucidated. Here, we provide an overview of current knowledge regarding the regulatory network involving transcription factors, noncoding RNAs, and histone modifications involved in GA pathways. We also discuss the mechanisms of interaction between GAs and other hormones in plant height development. Finally, future directions for applying knowledge of the GA hormone in crop breeding are described.

Jasmonates Coordinate Secondary with Primary Metabolism

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.

Methyl jasmonate elicitation effect on the metabolic profile of cambial meristematic cells culture derived from sweet basil (Ocimum basilicum L.) in relation to antioxidant activity: Untargeted metabolomics study in a time-based approach

The undifferentiated cambial meristematic cell (CMC) has been recognized as a value-added production platform for plant natural products in comparison to the dedifferentiated plant cell line (DDC). In a time-based approach at 0, 24, 48, and 72 h, the present study aimed at investigating the phytochemical metabolome of methyl jasmonate (MeJA)-elicited CMC cultures derived from sweet basil (Ocimum basilicum L.), including primary and secondary metabolites analyzed using GC/TOF-MS post-silylation and RP-UPLC-C₁₈-FT-MS/MS, respectively, as well as the analysis of aroma composition using headspace SPME-GC-MS. The results revealed a stress response in primary metabolism manifested by an increase in amino and organic acids reaching their maximum levels after 48 (1.3-fold) and 72 (1.7-fold) h, respectively. In addition, phenolic acids (e.g., sagerinic acid, rosmarinic acid, and 3-O-methylrosmarinic acid) followed by flavonoid aglycones (e.g., salvigenin and 5,6,4'-trihydroxy-7,3'-dimethoxyflavone) were the most abundant with prominent increases at 48 (1.2-fold) and 72 (2.1-fold) h, respectively. The aroma was intensified by the elicitation along the time, especially after 48 and 72 h. Furthermore, multivariate data analyses, including principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) confirmed elicitation effect, especially post 48 and 72 h. The study further assessed the effect of MeJA elicitation on the antioxidant and polyphenolic content. The cultures at 48 h demonstrated a significant (p < 0.05) antioxidant activity concurrently with correlation with total polyphenolic content using Pearson's correlation. Our study provides new insights to the elicitation impact on primary and secondary metabolism, in addition to aroma profile, to orchestrate the stress response and in relation to antioxidant effect.

Gibberellin confers to the expression of TaGA-6D and negatively regulates the fertility of wheat with Aegilops juvenalis cytoplasm

As the trace signal molecules widely existing in plants, plant hormones can regulate physiological responses of plants at low concentrations. At present, the effect of plant endogenous hormones on wheat male fertility has attracted attention, but the molecular mechanism underlying fertility regulation is unclear. Given this, the anthers of five isonuclear alloplasmic male sterile lines and their maintainer line were RNA-sequenced. A gene TaGA-6D encoding gibberellin (GA) regulated protein was isolated, which was located to the nucleus, cell wall and/or cell membrane, and predominantly highly expressed in the anther of Ju706A, a male sterile line with Aegilops juvenalis cytoplasm. By spraying assay of GA with different concentrations on fertility line Ju706R, it was found that with the increase of exogenous GA concentration, the content of endogenous GA and expression level of TaGA-6D in anther gradually increased, and the fertility decreased. However, silencing of TaGA-6D partially restore the fertility of Ju706R sprayed with 1000ng/μl GA, and indicating that gibberellin can promote the expression of TaGA-6D and negatively regulates the fertility of wheat with Aegilops juvenalis cytoplasm, which providing new insights for understanding hormone regulation of male fertility in wheat.

Jasmonic Acid as a Mediator in Plant Response to Necrotrophic Fungi

Jasmonic acid (JA) and its derivatives, all named jasmonates, are the simplest phytohormones which regulate multifarious plant physiological processes including development, growth and defense responses to various abiotic and biotic stress factors. Moreover, jasmonate plays an important mediator's role during plant interactions with necrotrophic oomycetes and fungi. Over the last 20 years of research on physiology and genetics of plant JA-dependent responses to pathogens and herbivorous insects, beginning from the discovery of the JA co-receptor CORONATINE INSENSITIVE1 (COI1), research has speeded up in gathering new knowledge on the complexity of plant innate immunity signaling. It has been observed that biosynthesis and accumulation of jasmonates are induced specifically in plants resistant to necrotrophic fungi (and also hemibiotrophs) such as mostly investigated model ones, i.e., Botrytis cinerea, Alternaria brassicicola or Sclerotinia sclerotiorum. However, it has to be emphasized that the activation of JA-dependent responses takes place also during susceptible interactions of plants with necrotrophic fungi. Nevertheless, many steps of JA function and signaling in plant resistance and susceptibility to necrotrophs still remain obscure. The purpose of this review is to highlight and summarize the main findings on selected steps of JA biosynthesis, perception and regulation in the context of plant defense responses to necrotrophic fungal pathogens.

Integrated metabolomic and transcriptomic analysis reveals the role of phenylpropanoid biosynthesis pathway in tomato roots during salt stress

As global soil salinization continues to intensify, there is a need to enhance salt tolerance in crops. Understanding the molecular mechanisms of tomato (Solanum lycopersicum) roots' adaptation to salt stress is of great significance to enhance its salt tolerance and promote its planting in saline soils. A combined analysis of the metabolome and transcriptome of S. lycopersicum roots under different periods of salt stress according to changes in phenotypic and root physiological indices revealed that different accumulated metabolites and differentially expressed genes (DEGs) associated with phenylpropanoid biosynthesis were significantly altered. The levels of phenylpropanoids increased and showed a dynamic trend with the duration of salt stress. Ferulic acid (FA) and spermidine (Spd) levels were substantially up-regulated at the initial and mid-late stages of salt stress, respectively, and were significantly correlated with the expression of the corresponding synthetic genes. The results of canonical correlation analysis screening of highly correlated DEGs and construction of regulatory relationship networks with transcription factors (TFs) for FA and Spd, respectively, showed that the obtained target genes were regulated by most of the TFs, and TFs such as MYB, Dof, BPC, GRAS, and AP2/ERF might contribute to the regulation of FA and Spd content levels. Ultimately, FA and Spd attenuated the harm caused by salt stress in S. lycopersicum, and they may be key regulators of its salt tolerance. These findings uncover the dynamics and possible molecular mechanisms of phenylpropanoids during different salt stress periods, providing a basis for future studies and crop improvement.

Lipoxygenase (LOX) in Sweet and Hot Pepper (Capsicum annuum L.) Fruits during Ripening and under an Enriched Nitric Oxide (NO) Gas Atmosphere

Lipoxygenases (LOXs) catalyze the insertion of molecular oxygen into polyunsaturated fatty acids (PUFA) such as linoleic and linolenic acids, being the first step in the biosynthesis of a large group of biologically active fatty acid (FA)-derived metabolites collectively named oxylipins. LOXs are involved in multiple functions such as the biosynthesis of jasmonic acid (JA) and volatile molecules related to the aroma and flavor production of plant tissues, among others. Using sweet pepper (Capsicum annuum L.) plants as a model, LOX activity was assayed by non-denaturing polyacrylamide gel electrophoresis (PAGE) and specific in-gel activity staining. Thus, we identified a total of seven LOX isozymes (I to VII) distributed among the main plant organs (roots, stems, leaves, and fruits). Furthermore, we studied the FA profile and the LOX isozyme pattern in pepper fruits including a sweet variety (Melchor) and three autochthonous Spanish varieties that have different pungency levels (Piquillo, Padrón, and Alegría riojana). It was observed that the number of LOX isozymes increased as the capsaicin content increased in the fruits. On the other hand, a total of eight CaLOX genes were identified in sweet pepper fruits, and their expression was differentially regulated during ripening and by the treatment with nitric oxide (NO) gas. Finally, a deeper analysis of the LOX IV isoenzyme activity in the presence of nitrosocysteine (CysNO, a NO donor) suggests a regulatory mechanism via S-nitrosation. In summary, our data indicate that the different LOX isozymes are differentially regulated by the capsaicin content, fruit ripening, and NO.

The Green Leaf Volatile (Z)-3-Hexenyl Acetate Is Differently Emitted by Two Varieties of Tulbaghia violacea Plants Routinely and after Wounding

While studying aromas produced by the edible flowers of Tulbaghia violacea, we noticed a different production of (Z)-3-Hexenyl acetate (a green-leaf volatile, GLV) by purple (var. ‘Violacea’) and white (var. ‘Alba’) flowers. The white Tulbaghia flowers constantly emits (Z)-3-Hexenyl acetate, which is instead produced in a lower amount by the purple-flowered variety. Thus, we moved to analyze the production of (Z)-3-Hexenyl acetate by whole plants of the two varieties by keeping them confined under a glass bell for 5 h together with a SPME (Solid Phase Micro Extraction) fiber. Results show that six main volatile compounds are emitted by T. violacea plants: (Z)-3-Hexenyl acetate, benzyl alcohol, nonanal, decanal, (Z)-3-Hexenyl-α-methylbutyrate, and one unknown compound. By cutting at half-height of the leaves, the (Z)-3-Hexenyl acetate is emitted in high quantities from both varieties, while the production of (Z)-3-Hexenyl-α-methylbutyrate increases. (Z)-3-Hexenyl acetate is a GLV capable of stimulating plant defenses, attracting herbivores and their natural enemies, and it is also involved in plant-to-plant communication and defense priming. Thus, T. violacea could represent a useful model for the study of GLVs production and a ‘signal’ plant capable of stimulating natural defenses in the neighboring plants.

Insights into the Jasmonate Signaling in Basal Land Plant Revealed by the Multi-Omics Analysis of an Antarctic Moss Pohlia nutans Treated with OPDA

12-oxo-phytodienoic acid (OPDA) is a biosynthetic precursor of jasmonic acid and triggers multiple biological processes from plant development to stress responses. However, the OPDA signaling and relevant regulatory networks were largely unknown in basal land plants. Using an integrated multi-omics technique, we investigated the global features in metabolites and transcriptional profiles of an Antarctic moss (Pohlia nutans) in response to OPDA treatment. We detected 676 metabolites based on the widely targeted metabolomics approach. A total of 82 significantly changed metabolites were observed, including fatty acids, flavonoids, phenolic acids, amino acids and derivatives, and alkaloids. In addition, the transcriptome sequencing was conducted to uncover the global transcriptional profiles. The representative differentially expressed genes were summarized into functions including Ca2+ signaling, abscisic acid signaling, jasmonate signaling, lipid and fatty acid biosynthesis, transcription factors, antioxidant enzymes, and detoxification proteins. The integrated multi-omics analysis revealed that the pathways of jasmonate and ABA signaling, lipid and fatty acid biosynthesis, and flavonoid biosynthesis might dominate the molecular responses to OPDA. Taken together, these observations provide insights into the molecular evolution of jasmonate signaling and the adaptation mechanisms of Antarctic moss to terrestrial habitats.

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.

The Influence of Exogenous Jasmonic Acid on the Biosynthesis of Steroids and Triterpenoids in Calendula officinalis Plants and Hairy Root Culture

The interplay between steroids and triterpenoids, compounds sharing the same biosynthetic pathway but exerting distinctive functions, is an important part of the defense strategy of plants, and includes metabolic modifications triggered by stress hormones such as jasmonic acid. Two experimental models, Calendula officinalis hairy root cultures and greenhouse cultivated plants (pot plants), were applied for the investigation of the effects of exogenously applied jasmonic acid on the biosynthesis and accumulation of steroids and triterpenoids, characterized by targeted GC-MS (gas chromatography-mass spectroscopy) metabolomic profiling. Jasmonic acid elicitation strongly increased triterpenoid saponin production in hairy root cultures (up to 86-fold) and their release to the medium (up to 533-fold), whereas the effect observed in pot plants was less remarkable (two-fold enhancement of saponin biosynthesis after a single foliar application). In both models, the increase of triterpenoid biosynthesis was coupled with hampering the biomass formation and modifying the sterol content, involving stigmasterol-to-sitosterol ratio, and the proportions between ester and glycoside conjugates. The study revealed that various organs in the same plant can react differently to jasmonic acid elicitation; hairy root cultures are a useful in vitro model to track metabolic changes, and enhanced glycosylation (of both triterpenoids and sterols) seems to be important strategy in plant defense response.