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Abstract Background Gynostemma pentaphyllum, an ancient Chinese herbal medicine, serves as a natural source of gypenosides with significant medicinal properties. Basic helix-loop-helix (bHLH) transcription factors play pivotal roles in numerous biological processes, especially in the regulation of secondary metabolism in plants. However, the characteristics and functions of the bHLH genes in G. pentaphyllum remain unexplored, and their regulatory role in gypenoside biosynthesis remains poorly elucidated. Results This study identified a total of 111 bHLH members in G. pentaphyllum (GpbHLHs), categorizing them into 26 subgroups based on shared conserved motif compositions and gene structures. Collinearity analysis illustrated that segmental duplications predominately lead to the evolution of GpbHLHs, with most duplicated GpbHLH gene pairs undergoing purifying selection. Among the nine gypenoside-related GpbHLH genes, two GpbHLHs (GpbHLH15 and GpbHLH58) were selected for further investigation based on co-expression analysis and functional prediction. The expression of these two selected GpbHLHs was dramatically induced by methyl jasmonate, and their nuclear localization was confirmed. Furthermore, yeast one-hybrid and dual-luciferase assays demonstrated that GpbHLH15 and GpbHLH58 could bind to the promoters of the gypenoside biosynthesis pathway genes, such as GpFPS1, GpSS1, and GpOSC1, and activate their promoter activity to varying degrees. Conclusions In conclusion, our findings provide a detailed analysis of the bHLH family and valuable insights into the potential use of GpbHLHs to enhance the accumulation of gypenosides in G. pentaphyllum.

Abstract Background Cinnamomum cassia Presl, classified in the Lauraceae family, is widely used as a spice, but also in medicine, cosmetics, and food. Aroma is an important factor affecting the medicinal and flavoring properties of C. cassia, and is mainly determined by volatile organic compounds (VOCs); however, little is known about the composition of aromatic VOCs in C. cassia and their potential molecular regulatory mechanisms. Here, integrated transcriptomic and volatile metabolomic analyses were employed to provide insights into the formation regularity of aromatic VOCs in C. cassia bark at five different harvesting times. Results The bark thickness and volatile oil content were significantly increased along with the development of the bark. A total of 724 differentially accumulated volatiles (DAVs) were identified in the bark samples, most of which were terpenoids. Venn analysis of the top 100 VOCs in each period showed that twenty-eight aromatic VOCs were significantly accumulated in different harvesting times. The most abundant VOC, cinnamaldehyde, peaked at 120 months after planting (MAP) and dominated the aroma qualities. Five terpenoids, α-copaene, β-bourbonene, α-cubebene, α-funebrene, and δ-cadinene, that peaked at 240 MAP could also be important in creating C. cassia’s characteristic aroma. A list of 43,412 differentially expressed genes (DEGs) involved in the biosynthetic pathways of aromatic VOCs were identified, including phenylpropanoids, mevalonic acid (MVA) and methylerythritol phosphate (MEP). A gene-metabolite regulatory network for terpenoid and phenylpropanoid metabolism was constructed to show the key candidate structural genes and transcription factors involved in the biosynthesis of terpenoids and phenylpropanoids. Conclusions The results of our research revealed the composition and changes of aromatic VOCs in C. cassia bark at different harvesting stages, differentiated the characteristic aroma components of cinnamon, and illuminated the molecular mechanism of aroma formation. These foundational results will provide technical guidance for the quality breeding of C. cassia.

Cinnamomum cassia Presl is a major food spice as well as traditional herbal medicine with anti-inflammatory, analgesic, and stomachic properties, which must be dried to preserve its quality, but mostly by using traditional, ineffective drying method. In order to find a scientific drying method by evaluating different drying methods that could influence the quality of C. cassia, ten indices were employed to evaluate different drying methods in C. cassia using the Analytic Hierarchy Process (AHP) method though calculating the total scores and ranking the priority. Four quality markers (Q-Markers) (coumarin, cinnamyl alcohol, cinnamaldehyde and o-methoxycinnamaldehyde) were isolated from the samples and analyzed by high performance liquid chromatography (HPLC) method under different drying methods. The results showed that various drying methods had multiple effects on the physicochemical qualities, essential oil content, and Q-Marker contents. Compared with other drying methods, oven-drying of 45 °C (45OD) maintained optimal levels of color and aroma, it also significantly shortened the drying time by 225 h than traditionally shade-drying (SHD) method with the drying rate (48.35 %), and obtained the highest essential oil content (3.05 %) and Q-Marker contents (30.23 mg g−1). Furthermore, the ash content (4.22 %) were satisfied with the stipulation of Chinese pharmacopoeia in 45OD samples. Applying AHP allowed us to identify 45OD as the optimal drying method with the highest total score (9.00), followed by the traditional shade-drying (SHD) method (7.88). The present study is the first report to apply the AHP method for quality evaluation of drying processing in C. cassia. It can provide the theoretical basis for evaluating an excellent method for C. cassia drying processing, as well as the rational use of different drying methods to furtherly develop the high quality C. cassia industry.

IntroductionAbrus mollis Hance. (AM) is an important species used in southern Chinese medicine. It is mainly found in Guangdong and Guangxi provinces in China, and it is effective in the treatment of hepatitis. Endophytic bacteria are known to affect the growth and quality of medicinal plants. However, there are limited reports describing endophytic bacteria related to AM.MethodsIn the present study, Illumina-based 16S rRNA gene sequencing was used to investigate the endophytic bacterial communities of root nodules of AM at five sampling sites in Guangxi. In addition, 179 strains of endophytic bacteria were isolated and categorized into 13 haplotypes based on recA sequence analysis.ResultsThe phylogeny of the 16S rRNA gene sequences revealed a predominance of nonrhizobial endophytes. Microbial diversity analysis showed that Proteobacteria was the dominant phylum in all samples, while Bradyrhizobium was the dominant genus in different samples. An efficient strain, Rhizobium tropici FM-19, was screened and obtained through greenhouse experiments. The AM plants inoculated with this strain showed the best growth performance and high nitrogen fixation and nodulation capacity. Notably, total phenols and total flavonoids, important active components in AM, increased by 30.9 and 42.7%, respectively, after inoculation with Rhizobium tropici FM-19.DiscussionThis study provides insights into the complex microbial diversity of AM nodules and provides strain information for the efficient cultivation of AM.

Abstract Background Abrus cantoniensis Hance. (Ac) and Abrus mollis (Am), two edible and medicinal plants with economic value in southern China, belong to the Abrus genus. Due to its growth characteristics, Am often replaces Ac in folk medicine. However, the latest National Pharmacopeia of China only recommends Ac. The differences in the metabolite composition of the plants are directly related to the differences in their clinical efficacy. Results The difference in metabolites were analyzed using an untargeted metabolomic approach based on ultrahigh-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC‒ESI‒MS/MS). The roots (R), stems (S) and leaves (L) of the two varieties were examined, and 635 metabolites belonging to 8 classes were detected. A comparative study revealed clear variations in the metabolic profiles of the two plants, and the AmR group had more active ingredients (flavonoids and terpenoids) than the AcR group. The metabolites classified as flavonoids and triterpene saponins showed considerable variations among the various samples. Both Ac and Am had unique metabolites. Two metabolites (isovitexin-2''-xyloside and soyasaponin V) specifically belong to Ac, and nine metabolites (vitexin-2"-O-galactoside, ethyl salicylate, 6-acetamidohexanoic acid, rhein-8-O-glucoside, hederagenin-3-O-glucuronide-28-O-glucosyl(1,2)-glucoside, methyl dioxindole-3-acetate, veratric acid, isorhamnetin-3-O-sophoroside-7-O-rhamnoside, and isorhamnetin-3-O-sophoroside) specifically belong to Am. Conclusions The metabolite differences between Ac and Am cause the differences in their clinical efficacy. Our findings serve as a foundation for further investigation of biosynthesis pathways and associated bioactivities and provide guidance for the clinical application of traditional Chinese medicine.

The beneficial microbiome assist the plant in disease defense. The root, stem and seed of Sophora tonkinensis from wild type were germinated and grew healthily, but they in cultivated type were susceptible to insect and pathogen attack. In order to explore the possibility of disease control using beneficial endophytic fungal microbiome harbored in S. tonkinensis from healthy wild type, endophytic fungi were isolated from the root, stem and seed of S. tonkinensis from healthy wild type, and then were further identified based on morphological characters and ITS sequence characters. Phylogenetic tree, α-diversity index and β-diversity index were used to analyze the phylogenetic evolution, diversity and similarity among different endophytic fungal microbiomes. The pathogen-resistant function in vitro of endophytic fungal microbiome was determined by the agar plug method and flat-stand method. The results were as follows: (1) A total of 131 strains with 23 taxa, 108 strains with 23 taxa, and 64 strains with 11 taxa, were respectively isolated and identified from the root, stem and seed of S. tonkinensis; (2) More endemic genera and all endemic species, indicated that endophytic fungal microbiomes harbored in the root, stem and seed had tissue specificity in genus and species evolutionary tree; (3) The extremely low β-diversity between root-stem, root-seed, and stem-seed indicated that species similarity was very low among different endophytic fungal microbiomes; (4) The high α-diversity showed that endophytic fungal microbiomes harbored in the root, stem and seed were abundant biodiversity; (5) More than one third of the taxa antagonized pathogens in vitro. Endophytic fungal microbiome harbored in the root/stem showed strong broad-spectrum pathogenic bacteria/fungi-resistant function in vitro, and endophytic fungal microbiome harbored in the seed showed strong broad-spectrum pathogenic fungi-resistant function in vitro. These results indicated beneficial endophytic fungal microbiome with tissue-specificity, biodiversity structure, and strong broad-spectrum pathogen-resistant function in vitro, harbored in healthy root, stem and seed of S. tonkinensis from wild type, and might play an important role in pathogen resistance in host tissues. Such results will provide material and experimental basis for disease control in different tissues of S. tonkinensis using beneficial endophytic fungal microbiome.

Panax notoginseng is a valuable Chinese herb in China, and the root should be harvested between three and seven years after planting it. However, the growth of P. notoginseng is frequently hindered due to replanting failure. There have been numerous studies proving that the accumulation of allelochemicals in the soil is considered to be one of the reasons for the replanting failure of P. notoginseng. Biodegradation of allelochemical in soil has been shown to be an effective measure to alleviate continuous cropping obstacles, so screening allelochemical-degrading bacteria could provide biological resources for soil remediation. Based on this, this study adopted a research strategy of enrichment and domestication to isolate and screen saponin-degrading bacteria from the rhizosphere soil of P. notoginseng, which had been grown continuously for three years and more. Also, the highly active strains were identified by 16S rRNA gene analysis. In addition, the effect of highly active strain SC3 on degrading allelochemicals under different conditions was studied by HPLC. The results were as follows: (1) Eight strains of potentially degrading bacteria were successfully isolated from the rhizosphere soil of P. notoginseng. The results of the initial screening evaluation showed that strain SC3 had the best biodegradation effect on total saponins with 87.42% degradation rate. (2) Strain SC3 was identified as Stenotrophomonas sp. based on 16S rRNA gene analysis coupled with physiological and biochemical analyses. (3) The biodegradation of ginsenoside Rb1 by strain SC3 was stronger than its biodegradation of ginsenoside Rg1 under the same culture conditions. (4) The degradation of ginsenoside Rb1 by SC3 strain under liquid culture conditions was significantly affected by different factors, such as substrate concentration, inoculum amount and culture temperature. All the results indicate that the enrichment and domestication strategy can effectively screen allelochemical-degrading bacteria, and a possible application of strain SC3 in the bioremediation of saponin contamination in agricultural environments. The results provide biological resources for replanting soil remediation and theoretical basis for further study of saponin degradation mechanism.

The genus Stephania, which is rich in alkaloids, has been used as a traditional medicine or folklore herb against numerous ailments in China. However, the understanding of the variation within the genus Stephania is obscure, which limits the optimal utilization of the genus. An evaluation of the variation within the genus Stephania would help screen the ideal Stephania genotypes for drug utilization. In the present study, alkaloids in the tubers of four commonly cultivated Stephania species in China, i.e., the genotype Stephania kwangsiensis Lo. (SK-guangxi) from Guangxi Province and three Stephania yunnanensis H.S. Lo. genotypes (SY-xueteng, SY-hongteng, and SY-lvteng) sourced from Yunnan Province, were investigated, and the genus variations were compared. The results revealed significant variations in the abundance of alkaloids in tubers within the genus Stephania. The Stephania genotypes SY-xueteng and SY-hongteng showed a relatively high abundance of total alkaloids compared with the Stephania genotypes SK-guangxi and SY-lvteng. Specifically, the Stephania genotype SY-xueteng had a relatively high abundance of palmatine in tubers, and the Stephania genotype SY-hongteng exhibited a high abundance of stephanine in tubers. Our study provides foundations for further utilization of ideal Stephania genotypes by clarifying the variations in the alkaloid contents within the genus in China.

【Objective】The study was carried out to investigate the effects of different planting densities on the photosynthetic characteristics, yield and quality of Centella asiatica(L.) Urban, which will provide a theoretical basis for the improvement of yield and quality during artificial cultivation.【Method】Five different planting densities, including 30 000, 60 000, 120 000, 160 000, and 250 000 plants/hm2, were set in greenhouse by using single factor randomized block design.The Li-6400 portable photosynthesis measure system was used to determine the photosynthetic characteristics in leaves and the content of asiaticoside and madecassoside in herbs was determined by HPLC.【Result】The planting density had no significant effects on branching number, dry weight per plant, stem diameter, leaf thickness, petiole length, leaf length and width of C asiatica(L.) Urban seedlings among in five different densities. The chlorophyll content, net photosynthetic rate(Pn), stomatal conductance(Gs), intercellular CO2 concentration(Ci), and transpiration rate(Tr) increased gradually and then decreased with the increase of density. Although the highest Pn [(15.241 μmol CO2/(m2·s) ﹞ was appeared at the density of 120 000plants/hm2, there was no significant difference between 60 000 and 120 000 plants/hm2. The highest chlorophyll a, chlorophyll b, chlorophyll total content, Gs, Ci, and Tr were all appeared under the 60 000 plants/hm2, which was significantly higher than those of other treatments. With the increase of density, the fresh yield, the dry yield, and the drying rate showed a trend of first increasing and then decreasing, which were the highest(21.437 t/hm2, 4.196 t/hm2, and 19.599%, respectively) when the density was 60 000 plants/hm2. At the density of 60 000 plants/hm2, all the fresh yield, the dry yield, and the drying rate were significantly higher than those of other treatments. The total contents of asiaticoside and madecassoside ranged from 1.95%to 2.78% among different densities, which were exceeded the requirement of Chinese Pharmacopoeia Version 2020(0.8%).The contents of asiaticoside and madecassoside also showed a trend of first increasing and then decreasing as the increase of density, and the total contents of asiaticoside and madecassoside were the highest(2.73%) when the density was 60 000 plants/hm2. Correlation analysis results showed that there was a significantly positive correlation between fresh yield and Tr, and a significantly positive correlation were also appeared among dry yield and Tr, Gs as well as total chlorophyll.【Conclusion】Planting density of 60 000 plants/hm2 was the most appropriate for C. asiatica in greenhouse. Reasonably dense planting could effectively increase the photosynthetic characteristics, increase photosynthetic efficiency, and improve the yield and quality of medicinal plants.

Pyrrosia petiolosa (Christ) Ching has both medicinal and health benefits in China. The potential antioxidant activities of P. petiolosa, which are mainly attributed to its flavonoids, have attracted much attention in recent years. The present study aimed to determine the concentration of flavonoid components and evaluate the relative antioxidant activities of P. petiolosa from different geographic origins using a UPLC-MRM-MS-based metabolomics approach. In total, 97 flavonoid components were identified, and their concentrations in the samples from different geographic locations showed significant variation. Thirteen flavonoid components were identified as potential biomarkers for distinguishing between the two major regions, Guizhou (GZ) and Guangxi (GX). The GZ group showed higher total flavonoid content, free radical scavenging activities, and ferric reducing antioxidant power. The well positive correlations were found between the antioxidant capacities and some flavonoid markers. The ecogeographic factors, namely altitude and longitude, play a crucial role in the difference of antioxidant activities and flavonoids concentration. These results indicate that P. petiolosa is rich in flavonoid compounds and is a promising source of natural antioxidants, providing a basis for the quality control of P. petiolosa.

Abstract Bletilla striata (Thunb.) Reichb.f. (BS) is a traditional Chinese medicine with numerous beneficial effects. In our previous study, Aspergillus flavus was isolated from B. striata. To explore the physiological and molecular mechanisms of Aspergillus flavus elicitor (1-G4) that promoted Bletilla striata growth, in this study, we performed the determination of growth indexes and transcriptomics and metabolomics analysis under 5% and 10% 1-G4 conditions. Results showed that 1-G4 elicitor could significantly promote the growth and development of B. striata. With the increasing concentration of 1-G4 elicitor, the contents of SA, ICAld, and ME-IAA significantly increased while the IP and ACC contents decreased dramatically. A total of 1657 DEGs (763 up-regulated and 894 down-regulated) between the control (CK) and 5% elicitor (CK vs G5) and 2415 DEGs (1208 up-regulated and 1207 down-regulated) between the control and 10% elicitor (CK vs G10) were identified. Further, we found that 22, 38, and 2 unigenes were involved in ME-IAA, IP, and ACC, respectively. It was indicated that these unigenes might be involved in B. striata growth. Overall, the current study laid a theoretical foundation for the effective utilization of endophytic fungi and the optimization of germplasm resources of B. striata.

The growth of Panax notoginseng (Burk.) F. H. Chen is frequently hindered due to replanting failure. In the present study, the objective is to determine whether root exudates from P. notoginseng have autotoxicity and identification of allelochemicals from root exudates or rhizosphere soil. We investigated autotoxicity in P. notoginseng using seedling emergence bioassays and hydroponic culture. The allelochemicals in the soils and root exudates were identified with GC-MS, and the autotoxicity of the identified key allelochemicals was investigated by bioassay. The results showed that the root exudates, and extracts from consecutively cultivated soils also showed significant autotoxicity against seedling emergence and growth. In the non-renewed culture solution without activated charcoal (AC), the fresh and dry mass of P. notoginseng tubers of roots was reduced by about half compared to the addition with AC. A total of 44 different components from all samples were defined by GC-MS analyses. Furthermore, the results of multiple statistical analysis showed a t the difference among cultivated soil, uncultivated soil and root exudates. Bioassay of the identified allelochemicals revealed that benzoic acid, phthalic acid, palmitic acid, and stearic acid significantly affected the root growth of P. notoginseng. These substances at 100 μM more significantly decreased the number of lateral roots. Our results demonstrated that autotoxicity results in replant failure of P. notoginseng.

The R2R3-MYB gene family participates in several plant physiological processes, especially the regulation of the biosynthesis of secondary metabolites. However, little is known about the functions of R2R3-MYB genes in Gynostemma pentaphyllum (G. pentaphyllum), a traditional Chinese medicinal herb that is an excellent source of gypenosides (a class of triterpenoid saponins) and flavonoids. In this study, a systematic genome-wide analysis of the R2R3-MYB gene family was performed using the recently sequenced G. pentaphyllum genome. In total, 87 R2R3-GpMYB genes were identified and subsequently divided into 32 subgroups based on phylogenetic analysis. The analysis was based on conserved exon–intron structures and motif compositions within the same subgroup. Collinearity analysis demonstrated that segmental duplication events were majorly responsible for the expansion of the R2R3-GpMYB gene family, and Ka/Ks analysis indicated that the majority of the duplicated R2R3-GpMYB genes underwent purifying selection. A combination of transcriptome analysis and quantitative reverse transcriptase-PCR (qRT-PCR) confirmed that Gynostemma pentaphyllum myeloblastosis 81 (GpMYB81) along with genes encoding gypenoside and flavonol biosynthetic enzymes exhibited similar expression patterns in different tissues and responses to methyl jasmonate (MeJA). Moreover, GpMYB81 could bind to the promoters of Gynostemma pentaphyllum farnesyl pyrophosphate synthase 1 (GpFPS1) and Gynostemma pentaphyllum chalcone synthase (GpCHS), the key structural genes of gypenoside and flavonol biosynthesis, respectively, and activate their expression. Altogether, this study highlights a novel transcriptional regulatory mechanism that suggests that GpMYB81 acts as a “dual-function” regulator of gypenoside and flavonol biosynthesis in G. pentaphyllum.