Full-Length Transcriptome Analyses of Genes Involved in Triterpenoid Saponin Biosynthesis of Psammosilene tunicoides Hairy Root Cultures With Exogenous Salicylic Acid

Nitrogen-fixing bacteria promote growth and bioactive components accumulation of Astragalus mongholicus by regulating plant metabolism and rhizosphere microbiota

BACKGROUND

The excessive application of chemical fertilizers in the cultivation of Astragalus mongholicus Bunge results in a reduction in the quality of the medicinal plant and compromises the sustainable productivity of the soil. PGPB inoculant is a hot topic in ecological agriculture research. In the cultivation of Astragalus mongholicus, the screened nitrogen-fixing bacteria can promote plant growth, however, whether it can promote the accumulation of main bioactive components remains unknown. In this study, mixed inoculants containing 5 strains of growth promoting bacteria (Rhizobium T16 , Sinorhizobium T21 , Bacillus J1 , Bacillus G4 and Arthrobacter J2) were used in the field experiment. The metabolic substances in the root tissues of Astragalus mongholicus were identified during the harvest period by non-targeted metabolomics method, and the differential metabolites between groups were identified by statistical analysis. Meanwhile, high-throughput sequencing was performed to analyze the changes of rhizosphere soil and endophytic microbial community structure after mixed microbial treatment.

RESULTS

The results of non-targeted metabolism indicated a significant increase in the levels of 26 metabolites after treatment including 13 flavonoids, 3 saponins and 10 other components. The contents of three plant hormones (abscisic acid, salicylic acid and spermidine) also increased after treatment, which presumed to play an important role in regulating plant growth and metabolism. Studies on endosphere and rhizosphere bacterial communities showed that Rhzobiaceae, Micromonosporaceae, and Hypomicrobiaceae in endophytic, and Oxalobactereae in rhizosphere were significantly increased after treatment. These findings suggest their potential importance in plant growth promotion and secondary metabolism regulation.

CONCLUSIONS

This finding provides a basis for developing nitrogen-fixing bacteria fertilizer and improving the ecological planting efficiency of Astragalus mongholicus.

Evaluation of Salicylic Acid and Methyl Jasmonate as Elicitors in Phyllanthus acuminatus Hairy Roots by Non-Targeted Analysis Using High-Resolution Mass Spectrometry

Phyllanthus acuminatus has been studied for its vast medical and industrial potential. Phytochemical investigations reveal that the genus is a rich source of lignans, flavonoids, phenolics, terpenoids, and other metabolites. However, the phytochemical profile elucidation of this species still needs further research. The use of eliciting compounds such as salicylic acid and methyl jasmonate has managed to increase the production of secondary metabolites in plant cell cultures. Hairy roots of Phyllanthus acuminatus were produced in 250 mL flasks with a 16 h light/8 h darkness photoperiod under diffused light with a culture time of four weeks. The elicitors salicylic acid and methyl jasmonate were tested in 50 μM and 200 μM concentrations. Non-targeted analysis was done for the different treatments using HR-MS. Identified metabolites were grouped in phenylpropanoids, phenols, and mucic acids, and statistical analysis of relative concentrations was achieved. A significant change in phenols' relative concentrations appeared in the elicitations with salicylic acid. Because of the elicitation treatment, specific compounds increased their concentrations, some of which have known pharmacological effects and are used in treating chronic diseases. The best elicitation treatment was salicylic acid 50 μM as it increased by more than 100% the general content of phenols and phenylpropanoid derivates and triplicates the concentration of mucic acid derivates in treated hairy root extracts. The application of non-targeted analysis showed interesting changes in phytochemical concentration due to elicitation in Phyllanthus acuminatus hairy roots.

Full-length transcriptome characterization and comparative analysis of Gleditsia sinensis

As an economically important tree, Gleditsia sinensis Lam. is widely planted. A lack of background genetic information on G. sinensis hinders molecular breeding. Based on PacBio single-molecule real-time (SMRT) sequencing and analysis of G. sinensis, a total of 95,183 non-redundant transcript sequences were obtained, of which 93,668 contained complete open reading frames (ORFs), 2,858 were long non-coding RNAs (LncRNAs) and 18,855 alternative splicing (AS) events were identified. Genes orthologous to different Gleditsia species pairs were identified, stress-related genes had been positively selected during the evolution. AGA, AGG, and CCA were identified as the universal optimal codon in the genus of Gleditsia. EIF5A was selected as a suitable fluorescent quantitative reference gene. 315 Cytochrome P450 monooxygenases (CYP450s) and 147 uridine diphosphate (UDP)-glycosyltransferases (UGTs) were recognized through the PacBio SMRT transcriptome. Randomized selection of GsIAA14 for cloning verified the reliability of the PacBio SMRT transcriptome assembly sequence. In conclusion, the research data lay the foundation for further analysis of the evolutionary mechanism and molecular breeding of Gleditsia.

Natural products of pentacyclic triterpenoids: from discovery to heterologous biosynthesis

Covering: up to 2022Pentacyclic triterpenoids are important natural bioactive substances that are widely present in plants and fungi. They have significant medicinal efficacy, play an important role in reducing blood glucose and protecting the liver, and have anti-inflammatory, anti-oxidation, anti-fatigue, anti-viral, and anti-cancer activities. Pentacyclic triterpenoids are derived from the isoprenoid biosynthetic pathway, which generates common precursors of triterpenes and steroids, followed by cyclization with oxidosqualene cyclases (OSCs) and decoration via cytochrome P450 monooxygenases (CYP450s) and glycosyltransferases (GTs). Many biosynthetic pathways of triterpenoid saponins have been elucidated by studying their metabolic regulation network through the use of multiomics and identifying their functional genes. Unfortunately, natural resources of pentacyclic triterpenoids are limited due to their low content in plant tissues and the long growth cycle of plants. Based on the understanding of their biosynthetic pathway and transcriptional regulation, plant bioreactors and microbial cell factories are emerging as alternative means for the synthesis of desired triterpenoid saponins. The rapid development of synthetic biology, metabolic engineering, and fermentation technology has broadened channels for the accumulation of pentacyclic triterpenoid saponins. In this review, we summarize the classification, distribution, structural characteristics, and bioactivity of pentacyclic triterpenoids. We further discuss the biosynthetic pathways of pentacyclic triterpenoids and involved transcriptional regulation. Moreover, the recent progress and characteristics of heterologous biosynthesis in plants and microbial cell factories are discussed comparatively. Finally, we propose potential strategies to improve the accumulation of triterpenoid saponins, thereby providing a guide for their future biomanufacturing.

Impact of salicylic acid and calcium chloride on quality attributes of peach stored at refrigeration temperature

Salicylic acid (SA) in different concentration were used to assess its individual effect as well as combined impact with 3% calcium chloride (CaCl2) on Swat No. 8 variety of peach stored at refrigerated temperature (6 ± 2 °C) for 21 days. Interestingly, the results revealed that applying 2 mmol L-1 SA with 3% CaCl2 maintained maximum nutritional value and least decay percent (44.1%) as compared to other treatments during storage. Moreover, this combination also exhibited significant weight loss and chilling injury at 6 ± 2 °C whereas increased levels of total phenolic, flavonoids, tannin, alkaloid, ascorbic acid, and antioxidant activity were observed as compared to other treatments. The combination treatment (2 mmol L-1 SA with 3% CaCl2) maintained other sensory attributes of peach fruit during refrigerated storage, therefore, its commercial use was recommended to store peach fruit for up to three weeks without any significant nutritional and physical loss.

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.

Effect of biotic stress on the presence of secondary metabolites in field pea grains

BACKGROUND

The presence of secondary metabolites responsible for off-flavours in peas may influence consumers' acceptance. These undesirable compounds may increase due to biotic stress or cultivar. Therefore, grains from two pea (Pisum sativum L.) cultivars (Crécerelle and Firenza) exposed to biotic stress were studied in terms of protein content, electrophoretic polypeptide profile, lipoxygenase activity, saponin content and volatile compounds.

RESULTS

No differences were observed in the electrophoretic polypeptide profile of pea samples across cultivar or biotic stress. The cultivar noticeably affected the volatile compounds and lipoxygenase activity. The biotic stress significantly increased the saponin content.

CONCLUSION

The cultivar showed more noticeable impact on the presence of off-flavour compounds than the biotic stress. The development of pea protein ingredients needs the thorough choice of raw materials in terms of cultivar and control of biotic stress in order to ensure acceptance by consumers. © 2022 Society of Chemical Industry.

Enhancement of Phytosterol and Triterpenoid Production in Plant Hairy Root Cultures-Simultaneous Stimulation or Competition?

Plant in vitro cultures, including hairy roots, can be applied for controlled production of valuable natural products, such as triterpenoids and sterols. These compounds originate from the common precursor squalene. Sterols and triterpenoids distinctly differ in their functions, and the 2,3-oxidosqualene cyclization step is often regarded as a branch point between primary and secondary (more aptly: general and specialized) metabolism. Considering the crucial role of phytosterols as membrane constituents, it has been postulated that unconstrained biosynthesis of triterpenoids can occur when sterol formation is already satisfied, and these compounds are no longer needed for cell growth and division. This hypothesis seems to follow directly the growth-defense trade-off plant dilemma. In this review, we present some examples illustrating the specific interplay between the two divergent pathways for sterol and triterpenoid biosynthesis appearing in root cultures. These studies were significant for revealing the steps of the biosynthetic pathway, understanding the role of particular enzymes, and discovering the possibility of gene regulation. Currently, hairy roots of many plant species can be considered not only as an efficient tool for production of phytochemicals, but also as suitable experimental models for investigations on regulatory mechanisms of plant metabolism.