Wound induced tanscriptional regulation of benzylisoquinoline pathway and characterization of wound inducible PsWRKY transcription factor from Papaver somniferum

Promising approaches for simultaneous enhancement of medicinally significant benzylisoquinoline alkaloids in opium poppy

Benzylisoquinoline alkaloids (BIAs) produced in opium poppy have been evidenced to heal patients suffering from various diseases. They, therefore, hold an integral position in the herbal drug industry. Despite the adoption of several approaches for the large-scale production of BIAs, opium poppy remains the only platform in this purpose. The only disadvantage associated with producing BIAs in the plant is their small quantity. Thus, recruiting strategies that boost their levels is deemed necessary. All the methods which have been employed so far are just able to enhance a maximum of two BIAs. Thus, if these methods are utilized, a sizable amount of time and budget must be spent on the synthesis of all BIAs. Hence, the exploitation of strategies which increase the content of all BIAs at the same time is more commercially effective and time-saving, avoiding the laborious step of resolving the biosynthetic pathway of each compound. Exposure to biotic and abiotic elicitors, development of a synthetic auto-tetraploid, overexpression of a WRKY transcription factor, formation of an artificial metabolon, and suppression of a gene in the shikimate pathway and miRNA are strategies that turn opium poppy into a versatile bioreactor for the concurrent and massive production of BIAs. The last three strategies have never been applied for BIA biosynthetic pathways.

The effects of green and chemically-synthesized copper oxide nanoparticles on the production and gene expression of morphinan alkaloids in Oriental poppy

Oriental poppy (Papaver orientale L.) belonging to the Papaveraceae family, has the capacity to synthesize a wide range of benzylisoquinoline alkaloids (BIAs). This experiment was conducted to investigate the effects of green and chemical copper oxide nanoparticles (CuO NPs) elicitors on oxidative stress and the BIAs biosynthesis pathway in the cell suspension culture of P. orientale. This research shows that both green and chemical CuO NPs at concentrations of 20 mg/L and 40 mg/L, induce oxidative stress in the cell suspension of P. orientale by increasing the production of H2O2 and the activity of antioxidant enzymes. The comparison of treatments revealed that utilizing a lower concentration of CuO NPs (20 mg/L) and extending the duration of cell suspension incubation (up to 48 h) play a more influential role in inducing the expression of the BIAs biosynthesis pathway genes (PsWRKY, TYDC, SalSyn, SalR, SalAT, T6ODM, COR and CODM) and increasing the production of morphinan alkaloids (thebaine, codeine, and morphine). The overarching results indicate that the concentration of CuO NPs and the duration of cell treatment have a more significant impact than the nature of CuO NPs in inducing oxidative stress and stimulating the expression of the BIAs pathway genes.

Histological, chemical and gene expression differences between western redcedar seedlings resistant and susceptible to cedar leaf blight

Introduction

Western redcedar (Thuja plicata) is an important species in the Cupressaceae both at economic and cultural levels in the Pacific Northwest of North America. In adult trees, the species produces one of the most weathering-resistant heartwoods among conifers, making it one of the preferred species for outdoor applications. However, young T. plicata plants are susceptible to infection with cedar leaf blight (Didymascella thujina), an important foliar pathogen that can be devastating in nurseries and small-spaced plantations. Despite that, variability in the resistance against D. thujina in T. plicata has been documented, and such variability can be used to breed T. plicata for resistance against the pathogen.

Objective

This investigation aimed to discern the phenotypic and gene expression differences between resistant and susceptible T. plicata seedlings to shed light on the potential constitutive resistance mechanisms against cedar leaf blight in western redcedar.

Methods

The study consisted of two parts. First, the histological differences between four resistant and four susceptible families that were never infected with the pathogen were investigated. And second, the differences between one resistant and one susceptible family that were infected and not infected with the pathogen were analyzed at the chemical (C, N, mineral nutrients, lignin, fiber, starch, and terpenes) and gene expression (RNA-Seq) levels.

Results

The histological part showed that T. plicata seedlings resistant to D. thujina had constitutively thicker cuticles and lower stomatal densities than susceptible plants. The chemical analyses revealed that, regardless of their infection status, resistant plants had higher foliar concentrations of sabinene and α-thujene, and higher levels of expression of transcripts that code for leucine-rich repeat receptor-like protein kinases and for bark storage proteins.

Conclusion

The data collected in this study shows that constitutive differences at the phenotypic (histological and chemical) and gene expression level exist between T. plicata seedlings susceptible and resistant to D. thujina. Such differences have potential use for marker-assisted selection and breeding for resistance against cedar leaf blight in western redcedar in the future.

Plant salinity stress, sensing, and its mitigation through WRKY

Salinity or salt stress has deleterious effects on plant growth and development. It imposes osmotic, ionic, and secondary stresses, including oxidative stress on the plants and is responsible for the reduction of overall crop productivity and therefore challenges global food security. Plants respond to salinity, by triggering homoeostatic mechanisms that counter salt-triggered disturbances in the physiology and biochemistry of plants. This involves the activation of many signaling components such as SOS pathway, ABA pathway, and ROS and osmotic stress signaling. These biochemical responses are accompanied by transcriptional modulation of stress-responsive genes, which is mostly mediated by salt-induced transcription factor (TF) activity. Among the TFs, the multifaceted significance of WRKY proteins has been realized in many diverse avenues of plants' life including regulation of plant stress response. Therefore, in this review, we aimed to highlight the significance of salinity in a global perspective, the mechanism of salt sensing in plants, and the contribution of WRKYs in the modulation of plants' response to salinity stress. This review will be a substantial tool to investigate this problem in different perspectives, targeting WRKY and offering directions to better manage salinity stress in the field to ensure food security.

A pervasive phosphorylation cascade modulation of plant transcription factors in response to abiotic stress

MAIN CONCLUSION

Transcriptional regulation of stress-responsive genes is a crucial step in establishing the mechanisms behind plant abiotic stress tolerance. A sensitive method of regulating transcription factors activity, stability, protein interaction, and subcellular localization is through phosphorylation. This review highlights a widespread regulation mechanism that involves phosphorylation of plant TFs in response to abiotic stress. Abiotic stress is one of the main components limiting crop yield and sustainability on a global scale. It greatly reduces the land area that is planted and lowers crop production globally. In all living organisms, transcription factors (TFs) play a crucial role in regulating gene expression. They participate in cell signaling, cell cycle, development, and plant stress response. Plant resilience to diverse abiotic stressors is largely influenced by TFs. Transcription factors modulate gene expression by binding to their target gene's cis-elements, which are impacted by genomic characteristics, DNA structure, and TF interconnections. In this review, we focus on the six major TFs implicated in abiotic stress tolerance, namely, DREB, bZIP, WRKY, ABF, MYB, and NAC, and the cruciality of phosphorylation of these transcription factors in abiotic stress signaling, as protein phosphorylation has emerged as one of the key post-translational modifications, playing a critical role in cell signaling, DNA amplification, gene expression and differentiation, and modification of other biological configurations. These TFs have been discovered after extensive study as stress-responsive transcription factors which may be major targets for crop development and important contributors to stress tolerance and crop production.

Genome-wide analysis of the WRKY genes and their important roles during cold stress in white clover

Background

White clover (Trifolium repens L) is a high-quality forage grass with a high protein content, but it is vulnerable to cold stress, which can negatively affect its growth and development. WRKY transcription factor is a family of plant transcription factors found mainly in higher plants and plays an important role in plant growth, development, and stress response. Although WRKY transcription factors have been studied extensively in other plants, it has been less studied in white clover.

Methods and Results

In the present research, we have performed a genome-wide analysis of the WRKY gene family of white clover, in total, there were 145 members of WRKY transcription factors identified in white clover. The characterization of the TrWRKY genes was detailed, including conserved motif analysis, phylogenetic analysis, and gene duplication analysis, which have provided a better understanding of the structure and evolution of the TrWRKY genes in white clover. Meanwhile, the genetic regulation network (GRN) containing TrWRKY genes was reconstructed, and Gene Ontology (GO) annotation analysis of these function genes showed they contributed to regulation of transcription process, response to wounding, and phosphorylay signal transduction system, all of which were important processes in response to abiotic stress. To determine the TrWRKY genes function under cold stress, the RNA-seq dataset was analyzed; most of TrWRKY genes were highly upregulated in response to cold stress, particularly in the early stages of cold stress. These results were validated by qRT-PCR experiment, implying they are involved in various gene regulation pathways in response to cold stress.

Conclusion

The results of this study provide insights that will be useful for further functional analyses of TrWRKY genes in response to biotic or abiotic stresses in white clover. These findings are likely to be useful for further research on the functions of TrWRKY genes and their role in response to cold stress, which is important to understand the molecular mechanism of cold tolerance in white clover and improve its cold tolerance.

Pistachio genomes provide insights into nut tree domestication and ZW sex chromosome evolution

Pistachio is a nut crop domesticated in the Fertile Crescent and a dioecious species with ZW sex chromosomes. We sequenced the genomes of Pistacia vera cultivar (cv.) Siirt, the female parent, and P. vera cv. Bagyolu, the male parent. Two chromosome-level reference genomes of pistachio were generated, and Z and W chromosomes were assembled. The ZW chromosomes originated from an autosome following the first inversion, which occurred approximately 8.18 Mya. Three inversion events in the W chromosome led to the formation of a 12.7-Mb (22.8% of the W chromosome) non-recombining region. These W-specific sequences contain several genes of interest that may have played a pivotal role in sex determination and contributed to the initiation and evolution of a ZW sex chromosome system in pistachio. The W-specific genes, including defA, defA-like, DYT1, two PTEN1, and two tandem duplications of six VPS13A paralogs, are strong candidates for sex determination or differentiation. Demographic history analysis of resequenced genomes suggest that cultivated pistachio underwent severe domestication bottlenecks approximately 7640 years ago, dating the domestication event close to the archeological record of pistachio domestication in Iran. We identified 390, 211, and 290 potential selective sweeps in 3 cultivar subgroups that underlie agronomic traits such as nut development and quality, grafting success, flowering time shift, and drought tolerance. These findings have improved our understanding of the genomic basis of sex determination/differentiation and horticulturally important traits and will accelerate the improvement of pistachio cultivars and rootstocks.

WRKY transcription factors: evolution, regulation, and functional diversity in plants

The recent advancements in sequencing technologies and informatic tools promoted a paradigm shift to decipher the hidden biological mysteries and transformed the biological issues into digital data to express both qualitative and quantitative forms. The transcriptomic approach, in particular, has added new dimensions to the versatile essence of plant genomics through the large and deep transcripts generated in the process. This has enabled the mining of super families from the sequenced plants, both model and non-model, understanding their ancestry, diversity, and evolution. The elucidation of the crystal structure of the WRKY proteins and recent advancement in computational prediction through homology modeling and molecular dynamic simulation has provided an insight into the DNA-protein complex formation, stability, and interaction, thereby giving a new dimension in understanding the WRKY regulation. The present review summarizes the functional aspects of the high volume of sequence data of WRKY transcription factors studied from different species, till date. The review focuses on the dynamics of structural classification and lineage in light of the recent information. Additionally, a comparative analysis approach was incorporated to understand the functions of the identified WRKY transcription factors subjected to abiotic (heat, cold, salinity, senescence, dark, wounding, UV, and carbon starvation) stresses as revealed through various sets of studies on different plant species. The review will be instrumental in understanding the events of evolution and the importance of WRKY TFs under the threat of climate change, considering the new scientific evidences to propose a fresh perspective.

Genomic profiling of WRKY transcription factors and functional analysis of CcWRKY7, CcWRKY29, and CcWRKY32 related to protoberberine alkaloids biosynthesis in Coptis chinensis Franch

Coptis chinensis Franch. (Huanglian in Chinese) is an important economic crop with medicinal value. Its rhizome has been used as a traditional herbal medicine for thousands of years in Asia. Protoberberine alkaloids, as the main bioactive component of Coptis chinensis, have a series of pharmacological activities. However, the protoberberine alkaloids content of C. chinensis is relatively low. Understanding the molecular mechanisms affecting the transcriptional regulation of protoberberine alkaloids would be crucial to increase their production via metabolic engineering. WRKY, one of the largest plant-specific gene families, regulates plant defense responses via the biosynthesis of specialized metabolites such as alkaloids. Totally, 41 WRKY transcription factors (TFs) related to protoberberine alkaloid biosynthesis were identified in the C. chinensis genome and classified into three groups based on phylogenetic and conserved motif analyses. Three WRKY genes (CcWRKY7, CcWRKY29, and CcWRKY32) may regulate protoberberine alkaloid biosynthesis, as suggested by gene-specific expression patterns, metabolic pathways, phylogenetic, and dual-luciferase analysis. Furthermore, the CcWRKY7, CcWRKY29, and CcWRKY32 proteins were specifically detected in the nucleus via subcellular localization. This study provides a basis for understanding the regulatory mechanisms of protoberberine alkaloid biosynthesis and valuable information for breeding C. chinensis varieties.

Ocimum sanctum, OscWRKY1, regulates phenylpropanoid pathway genes and promotes resistance to pathogen infection in Arabidopsis

KEY MESSAGE

OscWRKY1 from Ocimum sanctum positively regulates phenylpropanoid pathway genes and rosmarinic acid content. OscWRKY1 overexpression promotes resistance against bacterial pathogen in Arabidopsis. WRKY transcription factor (TF) family regulates various developmental and physiological functions in plants. PAL genes encode enzymes which are involved in plant defense responses, but the direct regulation of PAL genes and phenylpropanoid pathway through WRKY TF's is not well characterized. In the present study, we have characterized an OscWRKY1 gene from Ocimum sanctum which shows induced expression by methyl jasmonate (MeJA), salicylic acid (SA), and wounding. The recombinant OscWRKY1 protein binds to the DIG-labeled (Digoxigenin) W-box cis-element TTGAC[C/T] and activates the LacZ reporter gene in yeast. Overexpression of OscWRKY1 enhances Arabidopsis resistance towards Pseudomonas syringae pv. tomato Pst DC3000. Upstream activator sequences of PAL and C4H have been identified to contain the conserved W-box cis-element (TTGACC) in both O. sanctum and Arabidopsis. OscWRKY1 was found to interact with W-box cis-element present in the PAL and C4H promoters. Silencing of OscWRKY1 using VIGS resulted in reduced expression of PAL, C4H, COMT, F5H and 4CL transcripts. OscWRKY1 silenced plants exhibit reduced PAL activity, whereas, the overexpression lines of OscWRKY1 in Arabidopsis exhibit increased PAL activity. Furthermore, the metabolite analysis of OscWRKY1 silenced plants showed reduced rosmarinic acid content. These results revealed that OscWRKY1 positively regulates the phenylpropanoid pathway genes leading to the alteration of rosmarinic acid content and enhances the resistance against bacterial pathogen in Arabidopsis.

Interplay of transcription factors orchestrating the biosynthesis of plant alkaloids

Plants produce a range of secondary metabolites primarily as defence molecules. A plant has to invest considerable energy to synthesise alkaloids, and sometimes they are even toxic to themselves. Hence, the biosynthesis of alkaloids is a spatiotemporally regulated process under quantitative feedback regulation which is accomplished by the signal reception, transcriptional/translational regulation, transport, storage and accumulation. The transcription factors (TFs) initiate the biosynthesis of alkaloids after appropriate cues. The present study recapitulates last decade understanding of the role of TFs in alkaloid biosynthesis. The present review discusses TF families, viz. AP2/ERF, bHLH, WRKY, MYB involved in the biosynthesis of various types of alkaloids. It also highlights the role of the jasmonic acid cascade and post-translational modifications of TF proteins. A thorough understanding of TFs will help us to decide a strategy to facilitate successful pathway manipulation and in vitro production.

Transcription Factors in Alkaloid Engineering

Plants produce a large variety of low-molecular-weight and specialized secondary compounds. Among them, nitrogen-containing alkaloids are the most biologically active and are often used in the pharmaceutical industry. Although alkaloid chemistry has been intensively investigated, characterization of alkaloid biosynthesis, including biosynthetic enzyme genes and their regulation, especially the transcription factors involved, has been relatively delayed, since only a limited number of plant species produce these specific types of alkaloids in a tissue/cell-specific or developmental-specific manner. Recent advances in molecular biology technologies, such as RNA sequencing, co-expression analysis of transcripts and metabolites, and functional characterization of genes using recombinant technology and cutting-edge technology for metabolite identification, have enabled a more detailed characterization of alkaloid pathways. Thus, transcriptional regulation of alkaloid biosynthesis by transcription factors, such as basic helix–loop–helix (bHLH), APETALA2/ethylene-responsive factor (AP2/ERF), and WRKY, is well elucidated. In addition, jasmonate signaling, an important cue in alkaloid biosynthesis, and its cascade, interaction of transcription factors, and post-transcriptional regulation are also characterized and show cell/tissue-specific or developmental regulation. Furthermore, current sequencing technology provides more information on the genome structure of alkaloid-producing plants with large and complex genomes, for genome-wide characterization. Based on the latest information, we discuss the application of transcription factors in alkaloid engineering.

Transcriptional Factor-Mediated Regulation of Active Component Biosynthesis in Medicinal Plants

Plants produce thousands of chemically diverse secondary metabolites, many of which have valuable pharmaceutical properties. There is much interest in the synthesis of these pharmaceuticallyvaluable compounds, including the key enzymes and the transcription factors involved. The function and regulatory mechanism of transcription factors in biotic and abiotic stresses have been studied in depth. However, their regulatory roles in the biosynthesis of bioactive compounds, especially in medicinal plants, have only begun. Here, we review what is currently known about how transcription factors contribute to the synthesis of bioactive compounds (alkaloids, terpenoids, flavonoids, and phenolic acids) in medicinal plants. Recent progress has been made in the cloning and characterization of transcription factors in medicinal plants on the genome scale. So far, several large transcription factors have been identified in MYB, WRKY, bHLH, ZIP, AP2/ERF transcription factors. These transcription factors have been predicted to regulate bioactive compound production. These transcription factors positively or negatively regulate the expression of multiple genes encoding key enzymes, and thereby control the metabolic flow through the biosynthetic pathway. Although the research addressing this niche topic is in its infancy, significant progress has been made, and advances in high-throughput sequencing technology are expected to accelerate the discovery of key regulatory transcription factors in medicinal plants. This review is likely to be useful for those interested in the synthesis of pharmaceutically- valuable plant compounds, especially those aiming to breed or engineer plants that produce greater yields of these compounds.

Genome-Wide Profiling of WRKY Genes Involved in Benzylisoquinoline Alkaloid Biosynthesis in California Poppy (Eschscholzia californica)

Transcription factors of the WRKY family play pivotal roles in plant defense responses, including the biosynthesis of specialized metabolites. Based on the previous findings of WRKY proteins regulating benzylisoquinoline alkaloid (BIA) biosynthesis, such as CjWRKY1-a regulator of berberine biosynthesis in Coptis japonica-and PsWRKY1-a regulator of morphine biosynthesis in Papaver somniferum-we performed genome-wide characterization of the WRKY gene family in Eschscholzia californica (California poppy), which produces various BIAs. Fifty WRKY genes were identified by homology search and classified into three groups based on phylogenetic, gene structure, and conserved motif analyses. RNA sequencing showed that several EcWRKY genes transiently responded to methyl jasmonate, a known alkaloid inducer, and the expression patterns of these EcWRKY genes were rather similar to those of BIA biosynthetic enzyme genes. Furthermore, tissue expression profiling suggested the involvement of a few subgroup IIc EcWRKYs in the regulation of BIA biosynthesis. Transactivation analysis using luciferase reporter genes harboring the promoters of biosynthetic enzyme genes indicated little activity of subgroup IIc EcWRKYs, suggesting that the transcriptional network of BIA biosynthesis constitutes multiple members. Finally, we investigated the coexpression patterns of EcWRKYs with some transporter genes and discussed the diversified functions of WRKY genes based on a previous finding that CjWRKY1 overexpression in California poppy cells enhanced BIA secretion into the medium.

Characterization of LEA genes in Dendrobium officinale and one Gene in induction of callus

Late embryogenesis abundant (LEA) proteins are widely involved in plant stress responsive, while their involvement in callus formation is largest unknown. In this study, we identified and conducted expression analysis of the LEA genes from Phalaenopsis equestris and Dendrobium officinale, and characterized a LEA gene from D. officinale. A total 57 and 59 LEA genes were identified in P. equestris and D. officinale, respectively. A phylogenetic analysis showed that AtM, LEA_5 and Dehydrin groups were absent in both orchids. LEA_1 group genes were strongly expressed in seeds, significantly down-regulated in flowers, and absent in vegetative organs (leaves, stems and roots) in both orchids. Moreover, LEA_1 and LEA_4 group genes from D. officinale were abundant in the protocorm-like body stage and were dramatically up-regulated in response to abscisic acid and salinity stress. A LEA_1 gene (DoLEA43) was selected for further functional analysis. DoLEA43 protein was localized in the cytoplasm and nucleus, and its promoter contained a WUN-motif that was modulated by wounding. Overexpression of DoLEA43 in Arabidopsis enhanced callus induction, causing changes to callus formation-related genes such as WIND1. Our results indicate the involvement of LEA genes in the induction of callus, which provide insights into plant regeneration.

Altered gene expression and root thebaine production in polyploidized and methyl jasmonate-elicited Papaver bracteatum Lindl

Persian poppy (Papaver bracteatum Lindl.) is a perennial medicinal plant belonging to the Papaveraceae family that is endemic to the mountainous areas in Northern Iran. It is known for high amounts of the valuable benzylisoquinoline alkaloid thebaine. The effects of induced polyploidy as well as the effect of methyl Jasmonate (MeJA) elicitation on the root production of thebaine and on the expression of five alkaloid biosynthesis related genes were studied. The in vitro tetraploidy induction caused a significant increased expression of norcoclaurine synthase (NCS) and salutaridinol (SAT), and a significant decreased expression of berberine bridge enzyme (BBE) in the leaves. In the root tissues, the BBE, NCS, and SAT showed an increased expression in tetraploid plants, while codeinone reductase (COR) showed a decreased expression. A similar alteration pattern was found in mixoploid plants when compared to their diploid counterparts. MeJA at concentrations of 0.1 and 0.5 mM caused a remarkable increase in the thebaine content in the roots of treated plants, where the highest thebaine content was identified in plants elicited with 0.5 mM MeJA. Elicitation treatment caused a substantial increase in the expression of NCS and SAT in the leaves, while it had no major effect on BBE, codeine 3-O-demethylase (CODM) and COR. Expression analysis in the roots showed that MeJA caused a significant increase in the expression of only BBE and NCS, while expression of other studied genes remained unchanged. Our results may be exploited for improved thebaine production and the processing of Persian poppy.

Metabolic Profiling of Primary Metabolites and Galantamine Biosynthesis in Wounded Lycoris radiata Callus

Plants are continuously exposed to abiotic and biotic factors that lead to wounding stress. Different plants exhibit diverse defense mechanisms through which various important metabolites are synthesized. Humans can exploit these mechanisms to improve the efficacy of existing drugs and to develop new ones. Most previous studies have focused on the effects of wounding stress on the different plant parts, such as leaves, stems, and roots. To date, however, no study has investigated the accumulation of primary and galantamine content following the exposure of a callus to wounding stress. Therefore, in the present study, we exposed Lycoris radiata calli to wounding stress and assessed the expression levels of several genes involved in metabolic pathways at various time points (0, 3, 6, 12, 24, 48, 72, and 96 h of exposure). Furthermore, we quantify the primary and galantamine content using gas chromatography-time-of-flight mass spectrometry and the high-performance liquid chromatography qRT-PCR analysis of eight galantamine pathway genes (LrPAL-2, LrPAL-3, LrC4H-2, LrC3H, LrTYDC2, LrN4OMT, LrNNR, and LrCYP96T) revealed that seven genes, except LrN4OMT, were significantly expressed following exposure to wounding stress. Galantamine contents of calli after 3, 6, 12, 24, 48, 72, and 96 h of exposure were respectively 2.5, 2.5, 3.5, 3.5, 5.0, 5.0, and 8.5 times higher than that after 0 h of exposure. Furthermore, a total of 48 hydrophilic metabolites were detected in the 0 h exposed callus and 96 h exposed callus using GC-TOFMS. In particular, a strong positive correlation between galantamine and initial precursors, such as phenylalanine and tyrosine, was observed.

Genome-wide identification of AP2/ERF transcription factor-encoding genes in California poppy (Eschscholzia californica) and their expression profiles in response to methyl jasmonate

With respect to the biosynthesis of plant alkaloids, that of benzylisoquinoline alkaloids (BIAs) has been the most investigated at the molecular level. Previous investigations have shown that the biosynthesis of BIAs is comprehensively regulated by WRKY and bHLH transcription factors, while promoter analyses of biosynthesis enzyme-encoding genes have also implicated the involvement of members of the APETALA2/ethylene responsive factor (AP2/ERF) superfamily. To investigate the physiological roles of AP2/ERF transcription factors in BIA biosynthesis, 134 AP2/ERF genes were annotated using the draft genome sequence data of Eschscholzia californica (California poppy) together with transcriptomic data. Phylogenetic analysis revealed that these genes could be classified into 20 AP2, 5 RAV, 47 DREB, 60 ERF and 2 Soloist family members. Gene structure, conserved motif and orthologous analyses were also carried out. Gene expression profiling via RNA sequencing in response to methyl jasmonate (MeJA) indicated that approximately 20 EcAP2/ERF genes, including 10 group IX genes, were upregulated by MeJA, with an increase in the expression of the transcription factor-encoding gene EcbHLH1 and the biosynthesis enzyme-encoding genes Ec6OMT and EcCYP719A5. Further quantitative RT-PCR confirmed the MeJA responsiveness of the EcAP2/ERF genes, i.e., the increased expression of 9 group IX, 2 group X and 2 group III ERF subfamily genes. Transactivation activity of group IX EcAP2/ERFs was also confirmed by a luciferase reporter assay in conjunction with the promoters of the Ec6OMT and EcCYP719A5 genes. The physiological roles of AP2/ERF genes in BIA biosynthesis and their evolution in the regulation of alkaloid biosynthesis are discussed.

Asparagus racemosus bZIP transcription factor-regulated squalene epoxidase (ArSQE) promotes germination and abiotic stress tolerance in transgenic tobacco

A. racemosus is a rich source of pharmacologically active steroidal saponins. Most of the studies are related to its chemistry and pharmacology, but the pathway involved in the biosynthesis of steroidal saponin is not much emphasized. Squalene epoxidase acts as a rate-limiting enzyme in this biosynthesis. In this study, we have selected root specific squalene epoxidase ArSQE from A. racemosus for its characterization. ArSQE was able to complement ergosterol auxotrophy in erg1 yeast mutants. Mutants were sensitive to the antifungal drug terbinafine, whereas ArSQE complementation made them tolerant to the same drug. ArSQE plays a significant role in early germination in transgenic tobacco. The transgenic tobacco seedlings overexpressing ArSQE were tolerant to terbinafine and abiotic stress. Expression analysis of transcripts in ArSQE transgenic lines suggests that it mostly affects ABA, GA, stress, and sterol related functions in transgenic tobacco. Further, root specific MeJA responsive A. racemosus bZIP transcription factors (TFs), ArTGA1 and ArTGA2, were identified that bind to MeJA responsive cis-element present in the promoter region of ArSQE. Characterization of ArSQE of A. racemosus provides new information about its regulation through MeJA responsive bZIP TF along with its role in the development and abiotic stress response in transgenic tobacco.

Methyl jasmonate promote protostane triterpenes accumulation by up-regulating the expression of squalene epoxidases in Alisma orientale

Protostane triterpenes, which are found in Alisma orientale, are tetracyclic triterpenes with distinctive pharmacological activities. The natural distribution of protostane triterpenes is limited mainly to members of the botanical family Alismataceae. Squalene epoxidase (SE) is the key rate-limiting enzyme in triterpene biosynthesis. In this study, we report the characterization of two SEs from A. orientale. AoSE1 and AoSE2 were expressed as fusion proteins in E. coli, and the purified proteins were used in functional research. In vitro enzyme assays showed that AoSE1 and AoSE2 catalyze the formation of oxidosqualene from squalene. Immunoassays revealed that the tubers contain the highest levels of AoSE1 and AoSE2. After MeJA induction, which is the main elicitor of triterpene biosynthesis, the contents of 2,3-oxidosqualene and alisol B 23-acetate increased by 1.96- and 2.53-fold, respectively. In addition, the expression of both AoSE proteins was significantly increased at four days after MeJA treatment. The contents of 2,3-oxidosqualene and alisol B 23-acetate were also positively correlated with AoSEs expression at different times after MeJA treatment. These results suggest that AoSE1 and AoSE2 are the key regulatory points in protostane triterpenes biosynthesis, and that MeJA regulates the biosynthesis of these compounds by increasing the expression of AoSE1 and AoSE2.

PlWRKY13: A Transcription Factor Involved in Abiotic and Biotic Stress Responses in Paeonia lactiflora

Many members of the WRKY family regulate plant growth and development. Recent studies have shown that members of the WRKY family, specifically WRKY13, play various roles in the regulation of plant stress resistance. To study the function of WRKY family members in peony, the PlWRKY13 gene (KY271095) was cloned from peony leaves. Sequence analysis and subcellular localization results revealed that PlWRKY13 has no introns, belongs to the type IIc subgroup of the WRKY family, and functions in the nucleus. The expression pattern of PlWRKY13 was analysed via real-time quantitative RT-PCR (qRT-PCR), which showed that the expression of PlWRKY13 was induced by four types of abiotic stress, low-temperature, high-temperature, waterlogging and salt stress, and was positively upregulated in response to these stresses. In addition, the expression of PlWRKY13 tended to first decrease and then increase after infection with Alternaria tenuissima. Virus-induced gene silencing (VIGS) technology was used to explore the function of PlWRKY13 in the resistance of Paeonia lactiflora to fungal infection further, and the results showed that PlWRKY13-silenced plants displayed increased sensitivity to A. tenuissima. The infection was more severe and the disease index (DI) significantly greater in the PlWRKY13-silenced plants than in the control plants, and the expression of pathogenesis-related (PR) genes was also significantly altered in the PlWRKY13-silenced plants compared with the control plants. The contents of the endogenous hormones jasmonic acid (JA) and salicylic acid (SA) were measured, and the results showed that the JA content increased gradually after infection with A. tenuissima and that JA may play an active role in the resistance of P. lactiflora to pathogen infection, while the SA content decreased after PlWRKY13 silencing. The contents of the two hormones decreased overall, suggesting that they are related to the transcription of PlWRKY13 and that PlWRKY13 may be involved in the disease-resistance pathway mediated by JA and SA. In summary, the results of our study showed that PlWRKY13 expression was induced by stress and had a positive effect on the resistance of P. lactiflora to fungal infection.

Purification and Product Characterization of Lipoxygenase from Opium Poppy Cultures (Papaver somniferum L.)

Opium poppy (Papaver somniferum L.) is an ancient medicinal plant producing pharmaceutically important benzylisoquinoline alkaloids. In the present work we focused on the study of enzyme lipoxygenase (LOX, EC 1.13.11.12) from opium poppy cultures. LOX is involved in lipid peroxidation and lipoxygenase oxidation products of polyunsaturated fatty acids have a significant role in regulation of growth, development and plant defense responses to biotic or abiotic stress. The purpose of this study was to isolate and characterize LOX enzyme from opium poppy callus cultures. LOX was purified by ammonium sulfate precipitation and then followed by hydrophobic chromatography using Phenyl-Sepharose CL-4B and hydroxyapatite chromatography using HA Ultrogel sorbent. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis and immunoblotting revealed that LOX from opium poppy cultures was a single monomeric protein showing the relative molecular weight of 83 kDa. To investigate the positional specificity of the LOX reaction, purified LOX was incubated with linoleic acid and the products were analyzed by high-performance liquid chromatography in two steps, firstly with reverse phase (120-5 Nucleosil C18 column) and secondly with normal phase (Zorbax Rx-SIL column). LOX converted linoleic acid primarily to 13-hydroperoxy-(9Z,11E)-octadecadienoic acids (78%) and to a lesser extent 9-hydroperoxy-(10E,12Z)-octadecadienoic acids (22%). Characterization of LOX from opium poppy cultures provided valuable information in understanding LOX involvement in regulation of signaling pathways leading to biosynthesis of secondary metabolites with significant biological activity.

Comprehensive Analysis and Functional Studies of WRKY Transcription Factors in Nelumbo nucifera

The WRKY family is one of the largest transcription factor (TF) families in plants and plays central roles in modulating plant stress responses and developmental processes, as well as secondary metabolic regulations. Lotus (Nelumbo nucifera) is an aquatic crop that has significant food, ornamental and pharmacological values. Here, we performed an overview analysis of WRKY TF family members in lotus, and studied their functions in environmental adaptation and regulation of lotus benzylisoquinoline alkaloid (BIA) biosynthesis. A total of 65 WRKY genes were identified in the lotus genome and they were well clustered in a similar pattern with their Arabidopsis homologs in seven groups (designated I, IIa-IIe, and III), although no lotus WRKY was clustered in the group IIIa. Most lotus WRKYs were functionally paired, which was attributed to the recently occurred whole genome duplication in lotus. In addition, lotus WRKYs were regulated dramatically by salicilic acid (SA), jasmonic acid (JA), and submergence treatments, and two lotus WRKYs, NnWRKY40a and NnWRKY40b, were significantly induced by JA and promoted lotus BIA biosynthesis through activating BIA biosynthetic genes. The investigation of WRKY TFs for this basal eudicot reveals new insights into the evolution of the WRKY family, and provides fundamental information for their functional studies and lotus breeding.

3'O-Methyltransferase, Ps3'OMT, from opium poppy: involvement in papaverine biosynthesis

Using, in silico, in vitro and in planta functional assays, we demonstrate that Ps3'OMT, an 3'-O methyl transferase is linked to papaverine biosynthesis in opium poppy. Papaverine, one of the benzylisoquinoline alkaloids (BIA) synthesized in the medicinally important plant, Papaver somniferum, is known for the potent pharmacological properties. Papaverine biosynthesis has remained debatable as two different pathways, NH (involving N-desmethylated intermediates) and the NCH₃ (involving N-methylated intermediates), have been proposed. In addition, there are several intermediate steps in both the proposed pathways that are not very well characterized in terms of specific enzymes. In this study, we report the identification and functional characterization of 3'O-methyltransferase (Ps3'OMT) which might participate in the 3'O-methylation of the intermediates in the papaverine biosynthesis. Comparison of transcript and metabolite profiles of high and low papaverine producing cultivar revealed the occurrence of a 3'O-methyltransferase, Ps3'OMT, which was abundant in aerial organs and shared 72% identity with the GfLOMT7 predicted to have 3'OMT activity. In silico studies based on homology modeling, docking and MD simulations predicted (S)-norlaudanine as the potential substrate forming a stable complex with Ps3'OMT. Suppression of Ps3'OMT through virus-induced gene silencing resulted in a remarkable decrease in the level of papaverine in comparison to control plants. The characterization of the functionally unique Ps3'OMT involved in BIA metabolism suggests an involvement of the NH pathway leading to papaverine biosynthesis.

Genome-wide Analysis of the WRKY Gene Family and its Response to Abiotic Stress in Buckwheat (Fagopyrum Tataricum)

The WRKY gene family is an ancient plant transcription factor (TF) family with a vital role in plant growth and development, especially in response to biotic and abiotic stresses. Although many researchers have studied WRKY TFs in numerous plant species, little is known of them in Tartary buckwheat (Fagopyrum tataricum). Based on the recently reported genome sequence of Tartary buckwheat, we identified 78 FtWRKY proteins that could be classified into three major groups. All 77 WRKY genes were distributed unevenly across all eight chromosomes. Exon-intron analysis and motif composition prediction revealed the complexity and diversity of FtWRKYs, indicating that WRKY TFs may be of significance in plant growth regulation and stress response. Two separate pairs of tandem duplication genes were found, but no segmental duplications were identified. Overall, most orthologous gene-pairs between Tartary and common buckwheat evolved under strong purifying selection. qRT-PCR was used to analyze differences in expression among four FtWRKYs (FtWRKY6, 74, 31, and 7) under salt, drought, cold, and heat treatments. The results revealed that all four proteins are related to abiotic stress responses, although they exhibited various expression patterns. In particular, the relative expression levels of FtWRKY6, 74, and 31 were significantly upregulated under salt stress, while the highest expression of FtWRKY7 was observed from heat treatment. This study provides comprehensive insights into the WRKY gene family in Tartary buckwheat, and can support the screening of additional candidate genes for further functional characterization of WRKYs under various stresses.

Molecular Characterization of WRKY Transcription Factors That Act as Negative Regulators of O-Methylated Catechin Biosynthesis in Tea Plants ( Camellia sinensis L.)

Tea O-methylated catechins, especially (-)-epigallocatechin 3- O-(3- O-methyl)gallate (EGCG3″Me), have been attracting much attention as a result of their positive health effects. The transcription regulators of O-methylated catechin biosynthesis remain elusive. In this study, the expression pattern of genes related to O-methylated catechin biosynthesis, including CsLAR, CsANS, CsDFR, CsANR, and CCoAOMT, in three tea cultivars with different contents of EGCG3″Me was investigated. Two WRKY transcription factors (TFs), designated as CsWRKY31 and CsWRKY48, belonging to groups IIb and IIc of the WRKY family, respectively, were further identified. CsWRKY31 and CsWRKY48 were nuclear-localized proteins and possessed transcriptional repression ability. Furthermore, expression of CsWRKY31 and CsWRKY48 showed negative correlation with CsLAR, CsDFR, and CCoAOMT during EGCG3″Me accumulation in tea leaves. More importantly, W-box (C/T)TGAC(T/C) elements were located in the promoter of CsLAR, CsDFR, and CCoAOMT, and further assays revealed that CsWRKY31 and CsWRKY48 were capable of repressing the transcription of CsLAR, CsDFR, and CCoAOMT via the attachment of their promoters to the W-box elements. Collectively, our findings identify two novel negative regulators of O-methylated catechin biosynthesis in tea plants, which might provide a potential strategy to breed high-quality tea cultivar.

Coregulation of Biosynthetic Genes and Transcription Factors for Aporphine-Type Alkaloid Production in Wounded Lotus Provides Insight into the Biosynthetic Pathway of Nuciferine

Lotus (Nelumbo nucifera Gaertn.) contains various bioactive compounds, with benzylisoquinoline alkaloids (BIAs) as one of the major groups. The biosynthetic pathways of two major bioactive BIAs in this plant, nuciferine and N-nornuciferine, are still not clear. Therefore, several genes related to BIA biosynthesis were searched from the lotus database to study the role of key genes in regulating these pathways. In this study, the expression profiles of NCS, CNMT, 6OMT, CYP80G2, and WRKY TFs were investigated in mechanically wounded lotus leaves. It was found that the accumulation of nuciferine and N-nornuciferine significantly increased in the mechanically wounded lotus leaves in accordance with the relative expression of putative CYP80G2 and one WRKY transcription factor (NNU_24385), with the coregulation of CNMT. Furthermore, the role of methyltransferase-related genes in this study suggested that methylation of the isoquinoline nucleus to yield a methylated-BIA structure may occur at the N position before the O position. Altogether, this study provides improved understanding of the genes regulating BIA biosynthesis under stressed conditions, which could lead to improvements in BIA production from the commercial lotus.

Transcription factors WRKY11 and WRKY17 are involved in abiotic stress responses in Arabidopsis

Plant WRKY transcription factors play a vital role in abiotic stress tolerance and regulation of plant defense responses. This study examined AtWRKY11 and AtWRKY17 expression under ABA, salt, and osmotic stress at different developmental stages in Arabidopsis. We used reverse transcriptase PCR, quantitative real-time PCR, and promoter:GUS lines to analyze expression. Both genes were upregulated in response to abiotic stress. Next, we applied the same stressors to seedlings of T-DNA insertion wrky11 and 17 knock-out mutants (single and double). Under stress, the mutants exhibited slower germination and compromised root growth compared with the wild type. In most cases, double-mutant seedlings were more affected than single mutants. These results suggest that wrky11 and wrky17 are not strictly limited to plant defense responses but are also involved in conferring stress tolerance.

Evaluation of Manganese Chloride's Effect on Biosynthetic Properties of In Vitro Cultures of Eschscholzia californica Cham

The basal production of secondary metabolites in medicinal plants is limited. One of the effective approaches that encourages plants to produce a remarkable amount of precious compounds is an application of elicitors. Our work was focused on the elicitation of Eschscholzia californica Cham. suspension cultures using various concentrations of MnCl₂ (5; 10; 15 mg/L) with the aim of evaluating its effect on sanguinarine, chelerythrine, and macarpine production and gene expression of enzymes involved in the biosynthesis of mentioned secondary metabolites (BBE, 4′-OMT, CYP80B1) or in defense processes (LOX). Suspension cultures were exposed to elicitor for 24, 48, and 72 h. The content of alkaloids in phytomass was determined on the basis of their fluorescence properties. The relative mRNA expression of selected genes was analyzed using the ΔΔCt value method. PCR products were evaluated by melting curve analysis to confirm the specific amplification. Our results demonstrated that Eschscholzia californica Cham. cell suspension cultures evince sensitivity to the presence of MnCl₂ in growth media resulting in the increased production of benzophenanthridine alkaloids and gene expression of selected enzymes. Manganese chloride seems to be a potential elicitor supporting natural biosynthetic properties in plant cell cultures and can be applied for the sustained production of valuable secondary metabolites.

Inhibition of phospholipases influences the metabolism of wound-induced benzylisoquinoline alkaloids in Papaver somniferum L

Benzylisoquinoline alkaloids (BIAs) are important secondary plant metabolites and include medicinally relevant drugs, such as morphine or codeine. As the de novo synthesis of BIA backbones is (still) unfeasible, to date the opium poppy plant Papaver somniferum L. represents the main source of BIAs. The formation of BIAs is induced in poppy plants by stress conditions, such as wounding or salt treatment; however, the details about regulatory processes controlling BIA formation in opium poppy are not well studied. Environmental stresses, such as wounding or salinization, are transduced in plants by phospholipid-based signaling pathways, which involve different classes of phospholipases. Here we investigate whether pharmacological inhibition of phospholipase A₂ (PLA₂, inhibited by aristolochic acid (AA)) or phospholipase D (PLD; inhibited by 5-fluoro-2-indolyl des-chlorohalopemide (FIPI)) in poppy plants influences wound-induced BIA accumulation and the expression of key biosynthetic genes. We show that inhibition of PLA₂ results in increased morphinan biosynthesis concomitant with reduced production of BIAs of the papaverine branch, whereas inhibition of PLD results in increased production of BIAs of the noscapine branch. The data suggest that phospholipid-dependent signaling pathways contribute to the activation of morphine biosynthesis at the expense of the production of other BIAs in poppy plants. A better understanding of the effectors and the principles of regulation of alkaloid biosynthesis might be the basis for the future genetic modification of opium poppy to optimize BIA production.

Genome-wide characterization of the WRKY gene family in radish (Raphanus sativus L.) reveals its critical functions under different abiotic stresses

The radish WRKY gene family was genome-widely identified and played critical roles in response to multiple abiotic stresses. The WRKY is among the largest transcription factors (TFs) associated with multiple biological activities for plant survival, including control response mechanisms against abiotic stresses such as heat, salinity, and heavy metals. Radish is an important root vegetable crop and therefore characterization and expression pattern investigation of WRKY transcription factors in radish is imperative. In the present study, 126 putative WRKY genes were retrieved from radish genome database. Protein sequence and annotation scrutiny confirmed that RsWRKY proteins possessed highly conserved domains and zinc finger motif. Based on phylogenetic analysis results, RsWRKYs candidate genes were divided into three groups (Group I, II and III) with the number 31, 74, and 20, respectively. Additionally, gene structure analysis revealed that intron-exon patterns of the WRKY genes are highly conserved in radish. Linkage map analysis indicated that RsWRKY genes were distributed with varying densities over nine linkage groups. Further, RT-qPCR analysis illustrated the significant variation of 36 RsWRKY genes under one or more abiotic stress treatments, implicating that they might be stress-responsive genes. In total, 126 WRKY TFs were identified from the R. sativus genome wherein, 35 of them showed abiotic stress-induced expression patterns. These results provide a genome-wide characterization of RsWRKY TFs and baseline for further functional dissection and molecular evolution investigation, specifically for improving abiotic stress resistances with an ultimate goal of increasing yield and quality of radish.

Modulation of benzylisoquinoline alkaloid biosynthesis by heterologous expression of CjWRKY1 in Eschscholzia californica cells

Transcription factors control many processes in plants and have high potentials to manipulate specialized metabolic pathways. Transcriptional regulation of the biosynthesis of monoterpenoid indole alkaloids (MIAs), nicotine alkaloids, and benzylisoquinoline alkaloids (BIAs) has been characterized using Catharanthus roseus, Nicotiana and Coptis plants. However, metabolic engineering in which specific transcription factors are used in alkaloid biosynthesis is limited. In this study, we characterized the effects of ectopic expression of CjWRKY1, which is a transcriptional activator with many targets in BIA biosynthesis in Coptis japonica (Ranunculaceae) and Eschscholzia californica (California poppy, Papaveraceae). Heterologous expression of CjWRKY1 in cultured California poppy cells induced increases in transcripts of several genes encoding BIA biosynthetic enzymes. Metabolite analyses indicated that the overexpression of the CjWRKY1 gene also induced increases in the accumulation of BIAs such as sanguinarine, chelerythrine, chelirubine, protopine, allocryptopine, and 10-hydroxychelerythrine in the culture medium. Previous characterization of EcbHLH1 and current results indicated that both transcription factors, WRKY1 and bHLH1, are substantially involved in the regulation of BIA biosynthesis. We discuss the function of CjWRKY1 in E. californica cells and its potential for metabolic engineering in BIA biosynthesis.

StWRKY8 transcription factor regulates benzylisoquinoline alkaloid pathway in potato conferring resistance to late blight

The resistance to late blight is either qualitative or quantitative in nature. Quantitative resistance is durable, but challenging due to polygenic inheritance. In the present study, the diploid potato genotypes resistant and susceptible to late blight, were profiled for metabolites. Tissue specific metabolite analysis of benzylisoquinoline alkaloids (BIAs) in response to pathogen infection revealed increased accumulation of morphinone, codeine-6-glucuronide and morphine-3-glucuronides. These BIAs are antimicrobial compounds and possibly involved in cell wall reinforcement, especially through cross-linking cell wall pectins. Quantitative reverse transcription-PCR studies revealed higher expressions of TyDC, NCS, COR-2 and StWRKY8 transcription factor genes, in resistant genotypes than in susceptible genotype, following pathogen inoculation. A luciferase transient expression assay confirmed the binding of the StWRKY8 TF to promoters of downstream genes, elucidating a direct regulatory role on BIAs biosynthetic genes. Sequence analysis of StWRKY8 in potato genotypes revealed polymorphism in the WRKY DNA binding domain in the susceptible genotype, which is important for the regulatory function of this gene. A complementation assay of StWRKY8 in Arabidopsis wrky33 mutant background was associated with decreased fungal biomass. In conclusion, StWRKY8 regulates the biosynthesis of BIAs that are both antimicrobial and reinforce cell walls to contain the pathogen to initial infection.

NtWRKY-R1, a Novel Transcription Factor, Integrates IAA and JA Signal Pathway under Topping Damage Stress in Nicotiana tabacum

Topping damage can induce the nicotine synthesis in tobacco roots, which involves the activation of JA and auxin signal transduction. It remains unclear how these hormone signals are integrated to regulate nicotine synthesis. Here we isolated a transcription factor NtWRKY-R1 from the group IIe of WRKY family and it had strong negative correlation with the expression of putrescine N-methyltransferase, the key enzyme of nicotine synthesis pathway. NtWRKY-R1 was specifically and highly expressed in tobacco roots, and it contains two transcriptional activity domains in the N- and C-terminal. The promoter region of NtWRKY-R1 contains two cis-elements which are responding to JA and auxin signals, respectively. Deletion of NtWRKY-R1 promoter showed that JA and auxin signals were subdued by NtWRKY-R1, and the expression of NtWRKY-R1 was more sensitive to auxin than JA. Furthermore, Yeast two-hybrid experiment demonstrated that NtWRKY-R1 can interact with the actin-binding protein. Our data showed that the intensity of JA and auxin signals can be translated into the expression of NtWRKY-R1, which regulates the balance of actin polymerization and depolymerization through binding actin-binding protein, and then regulates the expression of genes related to nicotine synthesis. The results will help us better understand the function of the WRKY-IIe family in the signaling crosstalk of JA and auxin under damage stress.

Identification of a secretory phospholipase A2 from Papaver somniferum L. that transforms membrane phospholipids

The full-length sequence of a new secretory phospholipase A2 was identified in opium poppy seedlings (Papaver somniferum L.). The cDNA of poppy phospholipase A2, denoted as pspla2, encodes a protein of 159 amino acids with a 31 amino acid long signal peptide at the N-terminus. PsPLA2 contains a PLA2 signature domain (PA2c), including the Ca(2+)-binding loop (YGKYCGxxxxGC) and the catalytic site motif (DACCxxHDxC) with the conserved catalytic histidine and the calcium-coordinating aspartate residues. The aspartate of the His/Asp dyad playing an important role in animal sPLA2 catalysis is substituted by a serine residue. Furthermore, the PsPLA2 sequence contains 12 conserved cysteine residues to form 6 structural disulfide bonds. The calculated molecular weight of the mature PsPLA2 is 14.0 kDa. Based on the primary structure PsPLA2 belongs to the XIB group of PLA2s. Untagged recombinant PsPLA2 obtained by expression in Escherichia coli, renaturation from inclusion bodies and purification by cation-exchange chromatography was characterized in vitro. The pH optimum for activity of PsPLA2 was found to be pH 7, when using mixed micelles of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and Triton X-100. PsPLA2 specifically cleaves fatty acids from the sn-2 position of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine and shows a pronounced preference for PC over phosphatidyl ethanolamine, -glycerol and -inositol. The active recombinant enzyme was tested in vitro against natural phospholipids isolated from poppy plants and preferably released the unsaturated fatty acids, linoleic acid and linolenic acid, from the naturally occurring mixture of substrate lipids.

Comparative analysis of transcription factor gene families from Papaver somniferum: identification of regulatory factors involved in benzylisoquinoline alkaloid biosynthesis

Opium poppy (Papaver somniferum L.), known for biosynthesis of several therapeutically important benzylisoquinoline alkaloids (BIAs), has emerged as the premier organism to study plant alkaloid metabolism. The most prominent molecules produced in opium poppy include narcotic analgesic morphine, the cough suppressant codeine, the muscle relaxant papaverine and the anti-microbial agent sanguinarine and berberine. Despite several health benefits, biosynthesis of some of these molecules is very low due to tight temporal and spatial regulation of the genes committed to their biosynthesis. Transcription factors, one of the prime regulators of secondary plant product biosynthesis, might be involved in controlled biosynthesis of BIAs in P. somniferum. In this study, identification of members of different transcription factor gene families using transcriptome datasets of 10 cultivars of P. somniferum with distinct chemoprofile has been carried out. Analysis suggests that most represented transcription factor gene family in all the poppy cultivars is WRKY. Comparative transcriptome analysis revealed differential expression pattern of the members of a set of transcription factor gene families among 10 cultivars. Through analysis, two members of WRKY and one member of C3H gene family were identified as potential candidates which might regulate thebaine and papaverine biosynthesis, respectively, in poppy.

Genome-Wide Analysis of the Musa WRKY Gene Family: Evolution and Differential Expression during Development and Stress

The WRKY gene family plays an important role in the development and stress responses in plants. As information is not available on the WRKY gene family in Musa species, genome-wide analysis has been carried out in this study using available genomic information from two species, Musa acuminata and Musa balbisiana. Analysis identified 147 and 132 members of the WRKY gene family in M. acuminata and M. balbisiana, respectively. Evolutionary analysis suggests that the WRKY gene family expanded much before the speciation in both the species. Most of the orthologs retained in two species were from the γ duplication event which occurred prior to α and β genome-wide duplication (GWD) events. Analysis also suggests that subtle changes in nucleotide sequences during the course of evolution have led to the development of new motifs which might be involved in neo-functionalization of different WRKY members in two species. Expression and cis-regulatory motif analysis suggest possible involvement of Group II and Group III WRKY members during various stresses and growth/development including fruit ripening process respectively.

Characterization of the Promoter Region of Biosynthetic Enzyme Genes Involved in Berberine Biosynthesis in Coptis japonica

The presence of alkaloids is rather specific to certain plant species. However, berberine, an isoquinoline alkaloid, is relatively broadly distributed in the plant kingdom. Thus, berberine biosynthesis has been intensively investigated, especially using Coptis japonica cell cultures. Almost all biosynthetic enzyme genes have already been characterized at the molecular level. Particularly, two transcription factors (TFs), a plant-specific WRKY-type TF, CjWRKY1, and a basic helix-loop-helix TF, CjbHLH1, were shown to comprehensively regulate berberine biosynthesis in C. japonica cells. In this study, we characterized the promoter region of some biosynthetic enzyme genes and associated cis-acting elements involved in the transcriptional regulation via two TFs. The promoter regions of three berberine biosynthetic enzyme genes (CYP80B2, 4'OMT and CYP719A1) were isolated, and their promoter activities were dissected by a transient assay involving the sequentially truncated promoter::luciferase (LUC) reporter constructs. Furthermore, transactivation activities of CjWRKY1 were determined using the truncated promoter::LUC reporter constructs or constructs with mutated cis-elements. These results suggest the involvement of a putative W-box in the regulation of biosynthetic enzyme genes. Direct binding of CjWRKY1 to the W-box DNA sequence was also confirmed by an electrophoresis mobility shift assay and by a chromatin immunoprecipitation assay. In addition, CjbHLH1 also activated transcription from truncated 4'OMT and CYP719A1 promoters independently of CjWRKY1, suggesting the involvement of a putative E-box. Unexpected transcriptional activation of biosynthetic enzyme genes via a non-W-box sequence and by CjWRKY1 as well as the possible involvement of a GCC-box in berberine biosynthesis in C. japonica are discussed.

WRKY Transcription Factors: Molecular Regulation and Stress Responses in Plants

Plants in their natural habitat have to face multiple stresses simultaneously. Evolutionary adaptation of developmental, physiological, and biochemical parameters give advantage over a single window of stress but not multiple. On the other hand transcription factors like WRKY can regulate diverse responses through a complicated network of genes. So molecular orchestration of WRKYs in plant may provide the most anticipated outcome of simultaneous multiple responses. Activation or repression through W-box and W-box like sequences is regulated at transcriptional, translational, and domain level. Because of the tight regulation involved in specific recognition and binding of WRKYs to downstream promoters, they have become promising candidate for crop improvement. Epigenetic, retrograde and proteasome mediated regulation enable WRKYs to attain the dynamic cellular homeostatic reprograming. Overexpression of several WRKYs face the paradox of having several beneficial affects but with some unwanted traits. These overexpression-associated undesirable phenotypes need to be identified and removed for proper growth, development and yeild. Taken together, we have highlighted the diverse regulation and multiple stress response of WRKYs in plants along with the future prospects in this field of research.

Identification and expression analyses of MYB and WRKY transcription factor genes in Papaver somniferum L

Papaver somniferum L. is an herbaceous, annual and diploid plant that is important from pharmacological and strategic point of view. The cDNA clones of two putative MYB and WRKY genes were isolated (GeneBank accession numbers KP411870 and KP203854, respectively) from this plant, via the nested-PCR method, and characterized. The MYB transcription factor (TF) comprises 342 amino acids, and exhibits the structural features of the R2R3MYB protein family. The WRKY TF, a 326 amino acid-long polypeptide, falls structurally into the group II of WRKY protein family. Quantitative real-time PCR (qRT-PCR) analyses indicate the presence of these TFs in all organs of P. somniferum L. and Papaver bracteatum L. Highest expression levels of these two TFs were observed in the leaf tissues of P. somniferum L. while in P. bracteatum L. the espression levels were highest in the root tissues. Promoter analysis of the 10 co-expressed gene clustered involved in noscapine biosynthesis pathway in P. somniferum L. suggested that not only these 10 genes are co-expressed, but also share common regulatory motifs and TFs including MYB and WRKY TFs, and that may explain their common regulation.

Transcriptional responses and flavor volatiles biosynthesis in methyl jasmonate-treated tea leaves

BACKGROUND

Tea (Camellia sinensis) has long been consumed worldwide for its amazing flavor and aroma. Methyl jasmonate (MeJA), which acts as an effective elicitor among the plant kingdom, could mostly improve the quality of tea aroma by promoting flavor volatiles in tea leaves. Although a variety of volatile secondary metabolites that contribute to aroma quality have been identified, our understanding of the biosynthetic pathways of these compounds has remained largely incomplete. Therefore, information aboaut the transcriptome of tea leaves and, specifically, details of any changes in gene expression in response to MeJA, is required for a better understanding of the biological mechanisms of MeJA-mediated volatiles biosynthesis. Moreover, MeJA treatment could exaggerate the responses of secondary metabolites and some gene expression which offer a better chance to figure out the mechanism.

RESULTS

The results of two-dimensional gas-chromatograph mass-spectrometry showed that the terpenoids content in MeJA-treated tea leaves increased, especially linalool, geraniol, and phenylethyl alcohol. More importantly, we carried out RNA-seq to identify the differentially expressed genes (DEGs) related to volatiles biosynthesis pathways induced by MeJA treatment (0 h, 12 h, 24 h and 48 h) in tea leaves. We identified 19245, 18614, 11890 DEGs respectively in the MeJA_12h, MeJA_24 h and MeJA_48 h samples. The α-Lenolenic acid degradation pathway was firstly responded resulting in activating the JA-pathway inner tea leaves, and the MEP/DOXP pathway significantly exaggerated. Notably, the expression level of jasmonate O-methyltransferase, which is associated with the central JA biosynthesis pathway, was increased by 7.52-fold in MeJA_24 h tea leaves. Moreover, the genes related to the terpenoid backbone biosynthesis pathway showed different expression patterns compared with the untreated leaves. The expression levels of 1-deoxy-D-xylulose-phosphate synthase (DXS), all-trans-nonaprenyl-diphosphate synthase, geranylgeranyl reductase, geranylgeranyl diphosphate synthase (type II), hydroxymethylglutaryl-CoA reductase and 4-hydroxy-3-methylbut-2-enyl diphosphate reductase increased by approximately 2-4-fold.

CONCLUSIONS

The results of two-dimension gas-chromatography mass-spectrometry analysis suggested that exogenous application of MeJA could induce the levels of volatile components in tea leaves, especially the geraniol, linalool and its oxides. Moreover, the transcriptome analysis showed increased expression of genes in α-Lenolenic acid degradation pathway which produced massive jasmonic acid and quickly activated holistic JA-pathway inner tea leaves, also the terpenoid backbones biosynthesis pathway was significantly affected after MeJA treatment. In general, MeJA could greatly activate secondary metabolism pathways, especially volatiles. The results will deeply increase our understanding of the volatile metabolites biosynthesis pathways of tea leaves in response to MeJA.

PsAP2 an AP2/ERF family transcription factor from Papaver somniferum enhances abiotic and biotic stress tolerance in transgenic tobacco

The AP2/ERFs are one of the most important family of transcription factors which regulate multiple responses like stress, metabolism and development in plants. We isolated PsAP2 a novel AP2/ERF from Papaver somniferum which was highly upregulated in response to wounding followed by ethylene, methyl jasmonate and ABA treatment. PsAP2 showed specific binding with both DRE and GCC box elements and it was able to transactivate the reporter genes in yeast. PsAP2 overexpressing transgenic tobacco plants exhibited enhanced tolerance towards both abiotic and biotic stresses . Real time transcript expression analysis showed constitutive upregulation of tobacco Alternative oxidase1a and Myo-inositol-1-phosphate synthase in PsAP2 overexpressing tobacco plants. Further, PsAP2 showed interaction with NtAOX1a promoter in vitro, it also specifically activated the NtAOX1a promoter in yeast and tobacco BY2 cells. The silencing of PsAP2 using VIGS lead to significant reduction in the AOX1 level in P. somniferum. Taken together PsAP2 can directly bind and transcriptionally activate NtAOX1a and its overexpression in tobacco imparted increased tolerance towards both abiotic and biotic stress.

Metabolic transition in mycorrhizal tomato roots

Beneficial plant-microorganism interactions are widespread in nature. Among them, the symbiosis between plant roots and arbuscular mycorrhizal fungi (AMF) is of major importance, commonly improving host nutrition and tolerance against environmental and biotic challenges. Metabolic changes were observed in a well-established symbiosis between tomato and two common AMF: Rhizophagus irregularis and Funneliformis mosseae. Principal component analysis of metabolites, determined by non-targeted liquid chromatography-mass spectrometry, showed a strong metabolic rearrangement in mycorrhizal roots. There was generally a negative impact of mycorrhizal symbiosis on amino acid content, mainly on those involved in the biosynthesis of phenylpropanoids. On the other hand, many intermediaries in amino acid and sugar metabolism and the oxylipin pathway were among the compounds accumulating more in mycorrhizal roots. The metabolic reprogramming also affected other pathways in the secondary metabolism, mainly phenyl alcohols (lignins and lignans) and vitamins. The results showed that source metabolites of these pathways decreased in mycorrhizal roots, whilst the products derived from α-linolenic and amino acids presented higher concentrations in AMF-colonized roots. Mycorrhization therefore increased the flux into those pathways. Venn-diagram analysis showed that there are many induced signals shared by both mycorrhizal interactions, pointing to general mycorrhiza-associated changes in the tomato metabolome. Moreover, fungus-specific fingerprints were also found, suggesting that specific molecular alterations may underlie the reported functional diversity of the symbiosis. Since most positively regulated pathways were related to stress response mechanisms, their potential contribution to improved host stress tolerance is discussed.

Regulation of specialized metabolism by WRKY transcription factors

WRKY transcription factors (TFs) are well known for regulating plant abiotic and biotic stress tolerance. However, much less is known about how WRKY TFs affect plant-specialized metabolism. Analysis of WRKY TFs regulating the production of specialized metabolites emphasizes the values of the family outside of traditionally accepted roles in stress tolerance. WRKYs with conserved roles across plant species seem to be essential in regulating specialized metabolism. Overall, the WRKY family plays an essential role in regulating the biosynthesis of important pharmaceutical, aromatherapy, biofuel, and industrial components, warranting considerable attention in the forthcoming years.