Characterization of NAC family genes in Salvia miltiorrhiza and NAC2 potentially involved in the biosynthesis of tanshinones

Comprehensive analysis of the NAC transcription factor gene family in Sophora tonkinensis Gagnep

BACKGROUND

Sophora tonkinensis Gagnep. has long been utilized in the treatment of anti-inflammatory and pain-relieving, with its principal active compounds being alkaloids and flavonoids. NAC transcription factors, a large family of plant-specific regulators, play pivotal roles in growth, development, stress responses, and secondary metabolism. However, comprehensive genome-wide characterization of S. tonkinensis NAC gene family (StNAC) remains unexplored.

RESULTS

This study identified 85 NAC proteins from the S. tonkinensis genome database. Phylogenetic analysis revealed that StNAC proteins were categorized into 15 subgroups based on their homology with Arabidopsis thaliana NAC proteins. Gene structure analysis demonstrated a variation in intron numbers ranging from 1 to 7, with a majority of StNAC genes containing 2-3 introns. Chromosomal distribution analysis indicated an uneven spread of StNAC genes across 9 chromosomes, with the highest number of StNAC genes on Chr3. Detection of 4 tandem duplicates and 32 segmental duplicates revealed that segmental duplication primarily drive StNAC genes amplification. Prediction of cis-regulatory elements suggested the involvement of StNAC genes in growth, stress responses, and hormone regulation. Gene expression analysis showed substantial variability expression of StNAC genes across different tissues. Notably, eight StNAC genes were identified as significantly associated alkaloid and flavonoid levels. qRT-PCR validation indicated that five genes were highly expressed in tissues, corroborating transcriptome data.

CONCLUSION

These findings offer valuable insights for further functional characterization of NAC genes and their potential roles in alkaloid and flavonoid biosynthesis in S. tonkinensis.

Characterization of the NAC gene family in 'Fengdan' peony (Paeonia ostii) insights into the evolution and expression patterns under abiotic stresses and ABA treatment

Background

As one of the largest plant-specific transcription factor families, NAC proteins are crucial for plant growth and development processes and responses to various abiotic and biotic stresses. The published sequenced chromosome-level genome of 'Fengdan'peony provides a powerful tool for the analysis of the NAC gene family in this shrub.

Methods

The PoNAC gene family was identified and characterized using bioinformatic analysis, and RT-qPCR analysis was performed on some PoNACs from the ATAF and NAP subfamilies.

Results

In this study, a total of 82 NAC transcription factors (TFs) were identified in the 'Fengdan' peony genome, with the uneven anchorage of 78 PoNAC genes on 5 chromosomes, whereas only 4 PoNAC genes were found to be located on unanchored scaffolds. Through the phylogenetic analysis, 66 PoNAC genes were classified into 15 distinct subfamilies. The gene structure analysis revealed the variation in the number of exons from 0 to 14. Moreover, the motif analysis indicated that the identified PoNAC TFs possessed conserved NAC domains and motifs. The duplication events of PoNAC genes included whole-genome duplications (WGDs) or segmental duplications for 14 pairs, tandem duplications for 2 pairs, and proximal duplications for 3 pairs. GO analysis results suggested that the functions of PoNAC genes were mostly concentrated in the "biological process" GO category. Additionally, the analysis of the expression profiles of PoNAC genes in different plant organs revealed that only 45 genes were expressed in various tissues, some of them exhibited tissue-specific expression related to plant growth and development. RT-qPCR experiments demonstrated the responses of 8 genes from the ATAF and NAP subfamilies to ABA, heat and drought, suggesting that they may serve as important regulatory factor.

Multidimensional regulation of transcription factors: decoding the comprehensive signals of plant secondary metabolism

Plants synthesize an extensive array of secondary metabolites in response to diverse biotic and abiotic stresses. These metabolites function not only as defensive compounds but also constitute significant sources of nutrition and pharmaceuticals. However, the mechanisms governing the synthesis of these secondary metabolites have long been a central focus of research and continue to pose significant challenges. Transcription factors (TFs), serving as key regulators of secondary metabolite synthesis in plants, exhibit mechanisms of action that are still not fully understood. This review summarizes the latest research advancements on how plant transcription factors mediate the regulation of secondary metabolite biosynthesis through various signaling pathways, including light signaling, hormone signaling, MAPK signaling, the ubiquitin-proteasome pathway, epigenetic regulation, microbial interactions, and climate change. A deeper understanding of the mechanisms regulating transcription factors is expected to provide new insights into the biosynthesis of plant secondary metabolites.

New insights of advanced biotechnological engineering strategies for tanshinone biosynthesis in Salvia miltiorrhiza

Salvia miltiorrhiza Bunge, a well-known traditional Chinese herbal medicine, has been served as not only medicine for human ailments, but also health care products. As one of major bioactive ingredients, tanshinones are widely used to treat cardiovascular and cerebrovascular diseases, and also possess different pharmacological activities including anti-tumor, anti-inflammatory, anti-fibrotic and others. However, the content of tanshinones is relatively low in S. miltiorrhiza plants. Recently, multiple biotechnological strategies have been applied to improve tanshinone production. In this review, advances in bioactivities, biosynthesis pathway and regulation, transcriptional regulatory network, epigenetic modification and synthetic biology are summarized, and future perspectives are discussed, which will help develop high-quality S. miltiorrhiza resources.

Mining the Candidate Transcription Factors Modulating Tanshinones' and Phenolic Acids' Biosynthesis Under Low Nitrogen Stress in Salvia miltiorrhiza

Mining valuable genes is helpful to breed high-quality Salvia miltiorrhiza exhibiting efficient nitrogen fertilizer utilization efficiency. In the present study, transcriptome sequencing was introduced to select the candidate transcription factors (TFs) involved in tanshinones' (TAs) and phenolic acids' (PHAs) biosynthesis as well as low nitrogen (LN) stress. In totally, 97.71 Gb clean data was obtained from fifteen sequencing samples and 30,975 unigenes were assembled. Among of them, 27,843 unigenes were successfully annotated. Overall, 8663 differential expression genes (DEGs) were identified, among of which 5034 unigenes were up-regulated, and 3629 unigenes were down-regulated. By enrichment of DEGs together with gene co-expression network construction, 10 candidate TFs including HSFB2b, LBD12, ERF1A, ERF98, LBD25, HSF24, RAM1, HSFA4B, TCP8, and WRKY24 were finally retrieved, which are predicted to participate in modulating TA and PHA biosynthesis under LN stress. Quantitative real-time polymerase chain reaction (qRT-PCR) detection was introduced to further detect the expression profile of candidate TFs under LN stress. These findings offer a valuable resource for in-depth study of TAs 'and PHAs' biosynthesis under LN stress in S. miltiorrhiza.

The White Clover Single-Copy Nuclear Gene TrNAC002 Promotes Growth and Confers Drought Resistance in Plants Through Flavonoid Synthesis

White clover (Trifolium repens) is vulnerable to drought stress. In response to abiotic stress, plants are regulated by NAC transcription factors. The NAC in white clover has not been thoroughly documented until recently. We have identified one white clover NAC transcription factor called TrNAC002. TrNAC002's coding sequence is localized to specific regions on the 3P and 5O chromosomes of white clover and is part of a single-copy nuclear gene. Subcellular localization demonstrates that TrNAC002 is located in the nucleus, while the transcriptional activity assay indicates its transcriptional activity. Arabidopsis plants overexpressing TrNAC002 (OE) exhibit enlarged leaves and increased lateral root growth compared to the wild type (WT). Additionally, the expression levels of the shoot apical meristem (SAM), WUSCHEL (WUS), DNA-binding protein (DBP), and auxin-induced in root cultures3 (AIR3) genes are significantly higher in OE as compared to WT. These findings imply that TrNAC002 could promote vegetative growth by increasing the expression of these genes. Under natural drought stress, OE can survive in dry soil for a longer period of time than WT. Furthermore, OE exhibits a lower level of reactive oxygen species (ROS) level and a higher content of flavonoids than WT. This is also positively correlated with an increased flavonoid content. In white clover, the expression of TrNAC002, chalcone synthase (CHS), and chalcone isomerase (CHI) in leaves demonstrates significant upregulation after drought stress and ABA treatment, as does the flavonoid content. However, the pTRV-VIGS experiment suggests that pTRV2-TrNAC002 white clover shrinks compared to the Mock and Water controls. Additionally, pTRV2-TrNAC002 white clover displays a statistically higher malondialdehyde (MDA) content than the Mock and Water controls, and a significantly lower level of total antioxidant activities, flavonoid content, CHS and CHI relative expression than that of the Mock and Water controls. These findings indicate that TrNAC002 responds to drought and modulates flavonoid biosynthesis in white clover. This study is the first to suggest that TrNAC002 likely responds to drought via ABA and enhances plant drought resistance by synthesizing flavonoids.

Transcription factor PgNAC72 activates DAMMARENEDIOL SYNTHASE expression to promote ginseng saponin biosynthesis

Ginsenosides, the primary bioactive constituents in ginseng (Panax ginseng), possess substantial pharmacological potential and are in high demand in the market. The plant hormone methyl jasmonate (MeJA) effectively elicits ginsenoside biosynthesis in P. ginseng, though the regulatory mechanism remains largely unexplored. NAC transcription factors are critical in intricate plant regulatory networks and participate in numerous plant physiological activities. In this study, we identified a MeJA-responsive NAC transcription factor gene, PgNAC72, from a transcriptome library produced from MeJA-treated P. ginseng callus. Predominantly expressed in P. ginseng flowers, PgNAC72 localizes to the nucleus. Overexpressing PgNAC72 (OE-PgNAC72) in P. ginseng callus notably elevated total saponin levels, particularly dammarane-type ginsenosides, by upregulating dammarenediol synthase (PgDDS), encoding a key enzyme in the ginsenoside biosynthesis pathway. Electrophoretic mobility shift assays and dual-luciferase assays confirmed that PgNAC72 binds to the NAC-binding elements in the PgDDS promoter, thereby activating its transcription. Further RNA-seq and terpenoid metabolomic data in the OE-PgNAC72 line confirmed that PgNAC72 enhances ginsenoside biosynthesis. These findings uncover a regulatory role of PgNAC72 in MeJA-mediated ginsenoside biosynthesis, providing insights into the ginsenoside regulatory network and presenting a valuable target gene for metabolic engineering.

Biosynthesis and signal transduction of plant growth regulators and their effects on bioactive compound production in Salvia miltiorrhiza (Danshen)

Plant growth regulators (PGRs) are involved in multiple aspects of plant life, including plant growth, development, and response to environmental stimuli. They are also vital for the formation of secondary metabolites in various plants. Salvia miltiorrhiza is a famous herbal medicine and has been used commonly for > 2000 years in China, as well as widely used in many other countries. S. miltiorrhiza is extensively used to treat cardiovascular and cerebrovascular diseases in clinical practices and has specific merit against various diseases. Owing to its outstanding medicinal and commercial potential, S. miltiorrhiza has been extensively investigated as an ideal model system for medicinal plant biology. Tanshinones and phenolic acids are primary pharmacological constituents of S. miltiorrhiza. As the growing market for S. miltiorrhiza, the enhancement of its bioactive compounds has become a research hotspot. S. miltiorrhiza exhibits a significant response to various PGRs in the production of phenolic acids and tanshinones. Here, we briefly review the biosynthesis and signal transduction of PGRs in plants. The effects and mechanisms of PGRs on bioactive compound production in S. miltiorrhiza are systematically summarized and future research is discussed. This article provides a scientific basis for further research, cultivation, and metabolic engineering in S. miltiorrhiza.

Genome-wide analysis of NAC transcription factors and exploration of candidate genes regulating selenium metabolism in Broussonetia papyrifera

MAIN CONCLUSION

Genome-wide identification revealed 79 BpNAC genes belonging to 16 subfamilies, and their gene structures and evolutionary relationships were characterized. Expression analysis highlighted their importance in plant selenium stress responses. Paper mulberry (Broussonetia papyrifera), a deciduous arboreal plant of the Moraceae family, is distinguished by its leaves, which are abundant in proteins, polysaccharides, and flavonoids, positioning it as a novel feedstock. NAC transcription factors, exclusive to plant species, are crucial in regulating growth, development, and response to biotic and abiotic stress. However, extensive characterization of the NAC family within paper mulberry is lacking. In this study, 79 BpNAC genes were identified from the paper mulberry genome, with an uneven distribution across 13 chromosomes. A comprehensive, genome-wide analysis of BpNACs was performed, including investigating gene structures, promoter regions, and chromosomal locations. Phylogenetic tree analysis, alongside comparisons with Arabidopsis thaliana NACs, allowed for categorizing these genes into 16 subfamilies in alignment with gene structure and motif conservation. Collinearity analysis suggested a significant homologous relationship between the NAC genes of paper mulberry and those in Morus notabilis, Ficus hispida, Antiaris toxicaria, and Cannabis sativa. Integrating transcriptome data and Se content revealed that 12 BpNAC genes were associated with selenium biosynthesis. Subsequent RT-qPCR analysis corroborated the correlation between BpNAC59, BpNAC62 with sodium selenate, and BpNAC55 with sodium selenite. Subcellular localization experiments revealed the nuclear functions of BpNAC59 and BpNAC62. This study highlights the potential BpNAC transcription factors involved in selenium metabolism, providing a foundation for strategically breeding selenium-fortified paper mulberry.

Isolation, Characterization, and Expression Analysis of NAC Transcription Factor from Andrographis paniculata (Burm. f.) Nees and Their Role in Andrographolide Production

Andrographis paniculata (Burm. f.) Nees is an important medicinal plant known for its bioactive compound andrographolide. NAC transcription factors (NAM, ATAF1/2, and CUC2) play a crucial role in secondary metabolite production, stress responses, and plant development through hormonal signaling. In this study, a putative partial transcript of three NAC family genes (ApNAC83, ApNAC21 22 and ApNAC02) was used to isolate full length genes using RACE. Bioinformatics analyses such as protein structure prediction, cis-acting regulatory elements, and gene ontology analysis were performed. Based on in silico predictions, the diterpenoid profiling of the plant's leaves (five-week-old) and the real-time PCR-based expression analysis of isolated NAC genes under abscisic acid (ABA) treatment were performed. Additionally, the expression analysis of isolated NAC genes under MeJA treatment and transient expression in Nicotiana tabacum was performed. Full-length sequences of three members of the NAC transcription factor family, ApNAC83 (1102 bp), ApNAC21 22 (996 bp), and ApNAC02 (1011 bp), were isolated and subjected to the promoter and gene ontology analysis, which indicated their role in transcriptional regulation, DNA binding, ABA-activated signaling, and stress management. It was observed that ABA treatment leads to a higher accumulation of andrographolide and 14-deoxyandrographolide content, along with the upregulation of ApNAC02 (9.6-fold) and the downregulation of ApNAC83 and ApNAC21 22 in the leaves. With methyl jasmonate treatment, ApNAC21 22 expression decreased, while ApNAC02 increased (1.9-fold), with no significant change being observed in ApNAC83. The transient expression of the isolated NAC genes in a heterologous system (Nicotiana benthamiana) demonstrated their functional transcriptional activity, leading to the upregulation of the NtHMGR gene, which is related to the terpene pathway in tobacco. The expression analysis and heterologous expression of ApNAC21 22 and ApNAC02 indicated their role in andrographolide biosynthesis.

PnNAC2 promotes the biosynthesis of Panax notoginseng saponins and induces early flowering

KEY MESSAGE

PnNAC2 positively regulates saponin biosynthesis by binding the promoters of key biosynthetic genes, including PnSS, PnSE, and PnDS. PnNAC2 accelerates flowering through directly associating with the promoters of FT genes. NAC transcription factors play an important regulatory role in both terpenoid biosynthesis and flowering. Saponins with multiple pharmacological activities are recognized as the major active components of Panax notoginseng. The P. notoginseng flower is crucial for growth and used for medicinal and food purposes. However, the precise function of the P. notoginseng NAC transcription factor in the regulation of saponin biosynthesis and flowering remains largely unknown. Here, we conducted a comprehensive characterization of a specific NAC transcription factor, designated as PnNAC2, from P. notoginseng. PnNAC2 was identified as a nuclear-localized protein with transcription activator activity. The expression profile of PnNAC2 across various tissues mirrored the accumulation pattern of total saponins. Knockdown experiments of PnNAC2 in P. notoginseng calli revealed a significant reduction in saponin content and the expression level of pivotal saponin biosynthetic genes, including PnSS, PnSE, and PnDS. Subsequently, Y1H assays, dual-LUC assays, and electrophoretic mobility shift assays (EMSAs) demonstrated that PnNAC2 exhibits binding affinity to the promoters of PnSS, PnSE and PnDS, thereby activating their transcription. Additionally, an overexpression assay of PnNAC2 in Arabidopsis thaliana witnessed the acceleration of flowering and the induction of the FLOWERING LOCUS T (FT) gene expression. Furthermore, PnNAC2 demonstrated the ability to bind to the promoters of AtFT and PnFT genes, further activating their transcription. In summary, these results revealed that PnNAC2 acts as a multifunctional regulator, intricately involved in the modulation of triterpenoid saponin biosynthesis and flowering processes.

Comprehensive Analysis of NAC Transcription Factors Reveals Their Evolution in Malvales and Functional Characterization of AsNAC019 and AsNAC098 in Aquilaria sinensis

NAC is a class of plant-specific transcription factors that are widely involved in the growth, development and (a)biotic stress response of plants. However, their molecular evolution has not been extensively studied in Malvales, especially in Aquilaria sinensis, a commercial and horticultural crop that produces an aromatic resin named agarwood. In this study, 1502 members of the NAC gene family were identified from the genomes of nine species from Malvales and three model plants. The macroevolutionary analysis revealed that whole genome duplication (WGD) and dispersed duplication (DSD) have shaped the current architectural structure of NAC gene families in Malvales plants. Then, 111 NAC genes were systemically characterized in A. sinensis. The phylogenetic analysis suggests that NAC genes in A. sinensis can be classified into 16 known clusters and four new subfamilies, with each subfamily presenting similar gene structures and conserved motifs. RNA-seq analysis showed that AsNACs presents a broad transcriptional response to the agarwood inducer. The expression patterns of 15 AsNACs in A. sinensis after injury treatment indicated that AsNAC019 and AsNAC098 were positively correlated with the expression patterns of four polyketide synthase (PKS) genes. Additionally, AsNAC019 and AsNAC098 were also found to bind with the AsPKS07 promoter and activate its transcription. This comprehensive analysis provides valuable insights into the molecular evolution of the NAC gene family in Malvales plants and highlights the potential mechanisms of AsNACs for regulating secondary metabolite biosynthesis in A. sinensis, especially for the biosynthesis of 2-(2-phenyl) chromones in agarwood.

Analysis of WAK Genes in Nine Cruciferous Species with a Focus on Brassica napus L

The wall-associated kinase family contributes to plant cell elongation and pathogen recognition. Nine Cruciferous species were studied for identification and molecular evolution of the WAK gene family. Firstly, 178 WAK genes were identified. A phylogenetic tree was constructed of the Cruciferous WAK proteins into four categories, of which the Brassica rapa, Brassica oleracea and Brassica napus genes in the U's triangle were more closely related. The WAK gene family was unevenly distributed in B. napus chromosomal imaging, with the largest number of BnWAK genes located on chromosome C08. In the expression analysis, the expression patterns of the WAK gene family varied under different stress treatments, and some members of BnWAKs were significantly different under stress treatments. This study lays a foundation for further revealing the functional mechanisms of the WAK gene family in Brassica napus.

Comparative transcriptome analysis to identify putative genes involved in carvacrol biosynthesis pathway in two species of Satureja, endemic medicinal herbs of Iran

Satureja is rich in phenolic monoterpenoids, mainly carvacrol, that is of interest due to diverse biological activities including antifungal and antibacterial. However, limited information is available regarding the molecular mechanisms underlying carvacrol biosynthesis and its regulation for this wonderful medicinal herb. To identify the putative genes involved in carvacrol and other monoterpene biosynthesis pathway, we generated a reference transcriptome in two endemic Satureja species of Iran, containing different yields (Satureja khuzistanica and Satureja rechingeri). Cross-species differential expression analysis was conducted between two species of Satureja. 210 and 186 transcripts related to terpenoid backbone biosynthesis were identified for S. khuzistanica and S. rechingeri, respectively. 29 differentially expressed genes (DEGs) involved in terpenoid biosynthesis were identified, and these DEGs were significantly enriched in monoterpenoid biosynthesis, diterpenoid biosynthesis, sesquiterpenoid and triterpenoid biosynthesis, carotenoid biosynthesis and ubiquinone and other terpenoid-quinone biosynthesis pathways. Expression patterns of S. khuzistanica and S. rechingeri transcripts involved in the terpenoid biosynthetic pathway were evaluated. In addition, we identified 19 differentially expressed transcription factors (such as MYC4, bHLH, and ARF18) that may control terpenoid biosynthesis. We confirmed the altered expression levels of DEGs that encode carvacrol biosynthetic enzymes using quantitative real-time PCR (qRT-PCR). This study is the first report on de novo assembly and transcriptome data analysis in Satureja which could be useful for an understanding of the main constituents of Satureja essential oil and future research in this genus.

Comprehensive analysis of NAC transcription factors in Scutellaria baicalensis and their response to exogenous ABA and GA3

The NAC is a plant-specific family of transcription factor that plays important roles in various biological processes. Scutellaria baicalensis Georgi, belongs to the Lamiaceae family and has been widely used as a traditional herb with a wide range of pharmacological activities, including antitumor, heat-clearing, and detoxifying functions. However, no study on the NAC family in S. baicalensis has been conducted to date. In the present study, we identified 56 SbNAC genes using genomic and transcriptome analyses. These 56 SbNACs were unevenly distributed across nine chromosomes and were phylogenetically divided into six clusters. Cis-element analysis identified plant growth and development-, phytohormone-, light-, and stress-responsive elements were present in SbNAC genes promoter regions. Protein-protein interaction analysis was performed using Arabidopsis homologous proteins. Potential transcription factors, including bHLH, ERF, MYB, WRKY, and bZIP, were identified and constructed a regulatory network with SbNAC genes. The expression of 12 flavonoid biosynthetic genes was significantly upregulated with abscisic acid (ABA) and gibberellin (GA₃) treatments. Eight SbNAC genes (SbNAC9/32/33/40/42/43/48/50) also exhibited notable variation with two phytohormone treatments, among which SbNAC9 and SbNAC43 showed the most significant variation and deserved further study. Additionally, SbNAC44 displayed a positive correlation with C4H3, PAL5, OMT3, and OMT6, while SbNAC25 had negatively correlated with OMT2, CHI, F6H2, and FNSII-2. This study constitutes the first analysis of SbNAC genes and lays the basis foundation for further functional studies of SbNAC genes family members, while it may also facilitate the genetic improvement of plants and breeding of elite S. baicalensis varieties.

The NAC transcription factor family in Eucommia ulmoides: Genome-wide identification, characterization, and network analysis in relation to the rubber biosynthetic genes

The NAC transcription factor family is a large plant gene family, participating in plant growth and development, secondary metabolite synthesis, biotic and abiotic stresses responses, and hormone signaling. Eucommia ulmoides is a widely planted economic tree species in China that can produce trans-polyisoprene: Eucommia rubber (Eu-rubber). However, genome-wide identification of the NAC gene family has not been reported in E. ulmoides. In this study, 71 NAC proteins were identified based on genomic database of E. ulmoides. Phylogenetic analysis showed that the EuNAC proteins were distributed in 17 subgroups based on homology with NAC proteins in Arabidopsis, including the E. ulmoides-specific subgroup Eu_NAC. Gene structure analysis suggested that the number of exons varied from 1 to 7, and multitudinous EuNAC genes contained two or three exons. Chromosomal location analysis revealed that the EuNAC genes were unevenly distributed on 16 chromosomes. Three pairs of genes of tandem duplicates genes and 12 segmental duplications were detected, which indicated that segmental duplications may provide the primary driving force of expansion of EuNAC. Prediction of cis-regulatory elements indicated that the EuNAC genes were involved in development, light response, stress response and hormone response. For the gene expression analysis, the expression levels of EuNAC genes in various tissues were quite different. To explore the effect of EuNAC genes on Eu-rubber biosynthesis, a co-expression regulatory network between Eu-rubber biosynthesis genes and EuNAC genes was constructed, which indicated that six EuNAC genes may play an important role in the regulation of Eu-rubber biosynthesis. In addition, this six EuNAC genes expression profiles in E. ulmoides different tissues were consistent with the trend in Eu-rubber content. Quantitative real-time PCR analysis showed that EuNAC genes were responsive to different hormone treatment. These results will provide a useful reference for further studies addressing the functional characteristics of the NAC genes and its potential role in Eu-rubber biosynthesis.

Transcriptional regulatory network of high-value active ingredients in medicinal plants

High-value active ingredients in medicinal plants have attracted research attention because of their benefits for human health, such as the antimalarial artemisinin, anticardiovascular disease tanshinones, and anticancer Taxol and vinblastine. Here, we review how hormones and environmental factors promote the accumulation of active ingredients, thereby providing a strategy to produce high-value drugs at a low cost. Focusing on major hormone signaling events and environmental factors, we review the transcriptional regulatory network mediating biosynthesis of representative active ingredients. In this network, many transcription factors (TFs) simultaneously control multiple synthase genes; thus, understanding the molecular mechanisms affecting transcriptional regulation of active ingredients will be crucial to developing new breeding possibilities.

Transcriptome-wide identification of NAC (no apical meristem/Arabidopsis transcription activation factor/cup-shaped cotyledon) transcription factors potentially involved in salt stress response in garlic

Soil salinity has been an increasing problem worldwide endangering crop production and human food security. It is an ideal strategy to excavate stress resistant genes and develop salt tolerant crops. NAC (no apical meristem/Arabidopsis transcription activation factor/cup-shaped cotyledon) transcription factors have been demonstrated to be involved in salt stress response. However, relevant studies have not been observed in garlic, an important vegetable consumed in the world. In this study, a total of 46 AsNAC genes encoding NAC proteins were identified in garlic plant by transcriptome data. Phylogenetic analysis showed that the examined AsNAC proteins were clustered into 14 subgroups. Motif discovery revealed that the conserved domain region was mainly composed of five conserved subdomains. Most of the genes selected could be induced by salt stress in different tissues, indicating a potential role in salt stress response. Further studies may focus on the molecular mechanisms of the AsNAC genes in salt stress response. The results of the current work provided valuable resources for researchers aimed at developing salt tolerant crops.

Identification, classification, and expression profile analysis of heat shock transcription factor gene family in Salvia miltiorrhiza

In response to abiotic stresses, transcription factors are essential. Heat shock transcription factors (HSFs), which control gene expression, serve as essential regulators of plant growth, development, and stress response. As a model medicinal plant, Salvia miltiorrhiza is a crucial component in the treatment of cardiovascular illnesses. But throughout its growth cycle, S.miltiorrhiza is exposed to a series of abiotic challenges, including heat and drought. In this study, 35 HSF genes were identified based on genome sequencing of Salvia miltiorrhiza utilizing bioinformatics techniques. Additionally, 35 genes were classified into three groups by phylogeny and gene structural analysis, comprising 22 HSFA, 11 HSFB, and two HSFC. The distribution and sequence analysis of motif showed that SmHSFs were relatively conservative. In SmHSF genes, analysis of the promoter region revealed the presence of many cis-acting elements linked to stress, hormones, and growth and development, suggesting that these factors have regulatory roles. The majority of SmHSFs were expressed in response to heat and drought stress, according to combined transcriptome and real-time quantitative PCR (qRT-PCR) analyses. In conclusion, this study looked at the SmHSF gene family using genome-wide identification, evolutionary analysis, sequence characterization, and expression analysis. This research serves as a foundation for further investigations into the role of HSF genes and their molecular mechanisms in plant stress responses.

Soil applied silicon and manganese combined with foliar application of 5-aminolevulinic acid mediate photosynthetic recovery in Cd-stressed Salvia miltiorrhiza by regulating Cd-transporter genes

Salvia miltiorrhiza is an important medicinal plant that experiences significant growth and biomass losses when cultivated on cadmium (Cd) contaminated soils. High Cd accumulation in plant tissues also increases the risk of metal entry into the food chain. In this study, we proposed that Cd accumulation in S. miltiorrhiza can be restricted through plant growth regulators and nutrient management. Therefore, S. miltiorrhiza seedlings were transplanted into mixed nutrient soil for two weeks, then treated with 30 mg kg^-1 CdCl₂, 200 mg kg^-1 Na₂SiO₃·9H₂O, and 100 mg kg^-1 MnSO₄, and simultaneously sprayed with 10 mg L^-1 ALA on the leaves one week later. This study showed that elevated Cd accumulation significantly reduced plant growth and biomass. This growth inhibition damaged photosynthetic machinery and impaired carbon assimilation. In contrast, 5-aminolevulinic acid (ALA) significantly promoted the biomass of S. miltiorrhiza, and the dry weight of plants treated with ALA combined with manganese (Mn)/silicon (Si) increased by 42% and 55% as compared with Cd+Mn and Cd+Si treatments. Exogenously applied ALA and Si/Mn significantly activated antioxidant enzymes and promoted the growth recovery of S. miltiorrhiza. Further, exogenous ALA also reduced the Cd concentration in S. miltiorrhiza, especially when combined with Si. Compared with the Cd+Si treatment, the Cd+Si+ALA treatment reduced the Cd concentration in roots and leaves by 59% and 60%, respectively. Gene expression analysis suggested that ALA and Si significantly up-regulated genes associated with Cd transport. Other genes related to heavy metal tolerance mechanisms are also regulated to cope with heavy metal stress. These results indicated that the combined action of ALA and Si/Mn could reduce Cd-toxicity by increasing chlorophyll content and changing oxidative stress and can also affect Cd accumulation by regulating gene expression.

Proanthocyanidins Alleviate Cadmium Stress in Industrial Hemp (Cannabis sativa L.)

Industrial hemp (Cannabis sativa L.), an annual herbaceous cash crop, is widely used for the remediation of heavy metal-contaminated soils due to its short growth cycle, high tolerance, high biomass, and lack of susceptibility to transfer heavy metals into the human food chain. In this study, a significant increase in proanthocyanidins was found in Yunnan hemp no. 1 after cadmium stress. Proanthocyanidins are presumed to be a key secondary metabolite for cadmium stress mitigation. Therefore, to investigate the effect of proanthocyanidins on industrial hemp under cadmium stress, four experimental treatments were set up: normal environment, cadmium stress, proanthocyanidin treatment, and cadmium stress after pretreatment with proanthocyanidins. The phenotypes from the different treatments were compared. The experimental results showed that pretreatment with proanthocyanidins significantly alleviated cadmium toxicity in industrial hemp. The transcriptome and metabolome of industrial hemp were evaluated in the different treatments. Proanthocyanidin treatment and cadmium stress in industrial hemp mainly affected gene expression in metabolic pathways associated with glutathione metabolism, phenylpropanoids, and photosynthesis, which in turn altered the metabolite content in metabolic pathways of phenylalanine, vitamin metabolism, and carotenoid synthesis. The combined transcriptomic and metabolomic analysis revealed that proanthocyanidins mitigated cadmium toxicity by enhancing photosynthesis, secondary metabolite synthesis, and antioxidant synthesis. In addition, exogenous proanthocyanidins and cadmium ions acted simultaneously on EDS1 to induce the production of large amounts of salicylic acid in the plant. Finally, overexpression of CsANR and CsLAR, key genes for proanthocyanidins synthesis in industrial hemp, was established in Arabidopsis plants. The corresponding plants were subjected to cadmium stress, and the results showed that CsLAR transgenic plants were more tolerant to cadmium than the CsANR transgenic and wild-type Arabidopsis plants. The results showed that salicylic acid and jasmonic acid were increased in Arabidopsis overexpressing CsLAR compared to AT wild-type Arabidopsis, and levels of secondary metabolites were significantly higher in Arabidopsis overexpressing CsLAR than in AT wild-type Arabidopsis. These results revealed how proanthocyanidins alleviated cadmium stress and laid the foundation for breeding industrial hemp varieties with higher levels of proanthocyanidins and greater tolerance.

MAPKK2/4/5/7-MAPK3-JAZs modulate phenolic acid biosynthesis in Salvia miltiorrhiza

Phenolic acids are the major bioactive metabolites produced in Salvia miltiorrhiza, a traditional Chinese medicine called Danshen. Many phytohormone elicitor treatments induce phenolic acid biosynthesis, even though the underlying mechanism remains obscure. Expression pattern analysis showed that SmMAPK3 was highly expressed in leaves, and SmMAPK3 was significantly induced by salicylic acid (SA) and methyl jasmonate (JA). Bioinformatics analysis revealed that SmMAPK3 belongs to group A and contains a TEY motif in the activation loop together with three conserved regions (P-loop, C-loop and CD-domain). A previous study speculated that SmMAPK3 is likely a positive regulator in the biosynthesis of phenolic acids in S. miltiorrhiza. In this study, overexpression of SmMAPK3 increased phenolic acid biosynthetic gene expression and enhanced the accumulation of phenolic acids in S. miltiorrhiza plantlets. Yeast two-hybrid (Y2H) analysis and firefly luciferase complementation imaging (LCI) assays revealed that SmMAPKK2/4/5/7-SmMAPK3-SmJAZs form a cascade that regulates the accumulation of phenolic acids. In summary, this work deepens our understanding of the posttranscriptional regulatory mechanisms of phenolic acid biosynthesis and sheds new light on metabolic engineering in S. miltiorrhiza.