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

Mass spectrometry imaging and single-cell transcriptional profiling reveal the tissue-specific regulation of bioactive ingredient biosynthesis in Taxus leaves

Taxus leaves provide the raw industrial materials for taxol, a natural antineoplastic drug widely used in the treatment of various cancers. However, the precise distribution, biosynthesis, and transcriptional regulation of taxoids and other active components in Taxus leaves remain unknown. Matrix-assisted laser desorption/ionization-mass spectrometry imaging analysis was used to visualize various secondary metabolites in leaf sections of Taxus mairei, confirming the tissue-specific accumulation of different active metabolites. Single-cell sequencing was used to produce expression profiles of 8846 cells, with a median of 2352 genes per cell. Based on a series of cluster-specific markers, cells were grouped into 15 clusters, suggesting a high degree of cell heterogeneity in T. mairei leaves. Our data were used to create the first Taxus leaf metabolic single-cell atlas and to reveal spatial and temporal expression patterns of several secondary metabolic pathways. According to the cell-type annotation, most taxol biosynthesis genes are expressed mainly in leaf mesophyll cells; phenolic acid and flavonoid biosynthesis genes are highly expressed in leaf epidermal cells (including the stomatal complex and guard cells); and terpenoid and steroid biosynthesis genes are expressed specifically in leaf mesophyll cells. A number of novel and cell-specific transcription factors involved in secondary metabolite biosynthesis were identified, including MYB17, WRKY12, WRKY31, ERF13, GT_2, and bHLH46. Our research establishes the transcriptional landscape of major cell types in T. mairei leaves at a single-cell resolution and provides valuable resources for studying the basic principles of cell-type-specific regulation of secondary metabolism.

Cloning, subcellular localization and expression analysis of squalene epoxidase gene BsSE1 from Bletilla striata

Squalene epoxidase catalyzes the oxidation of squalene to 2,3-oxo-squalene (BsSE1), and is the key rate limiting enzyme in the synthesis of triterpenoids and sterols in plants. This study focused on the basic aspects of BsSE1 including the sequence information, sub-cellular localization expression patterns of BsSE1. Using to the sequence information of Bletilla striata transcriptome, the full-length CDS of BsSE1 gene was amplified. The physicochemical properties and structural characteristics of BsSE1 protein were analyzed by bioinformatics analysis software, and vector was constructed to analyze the protein locations and expression patterns. The results showed that the CDS of BsSE1 gene was 1542 bp, encoding 513 amino acids. BsSE1 protein is a hydrophobic protein with two transmembrane domains but no signal peptides. It is localied in the endoplasmic reticulum membrane and belongs to the typical squalene epoxidase gene. BsSE1 has the closest genetic relationship with SE protein of Dendrobium officinale and Phalaenopsis equestris. The expression level of BsSE1 was higher in pseudobulblet of Bletilla striata seedlings, followed by roots, and lower in seedling stems. After SA induction, the expression of BsSE1 in Bletilla striata showed significant changes, increased first, then decreased, finally increase again. The results provide a basis for further study of this gene family in plants.

Comparative transcriptome mining for terpenoid biosynthetic pathway genes in wild and cultivated species of Plantago

Plantagos are important economical and medicinal plants that possess several bioactive secondary metabolites, such as phenolics, iridoids, triterpenes, and alkaloids. Triterpenoids are the ubiquitous and dynamic secondary metabolites that are deployed by plants for chemical interactions and protection under biotic/abiotic stress. Plantago ovata, a cultivated species, is the source of psyllium, while Plantago major, a wild species, has significant therapeutic potential. Wild species are considered more tolerant to stressful conditions in comparison to their cultivated allies. In view of this, the present study aimed to decipher the terpenoid biosynthetic pathway operative in P. ovata and P. major using a comparative transcriptomics approach. Majority of terpenoid biosynthetic genes were observed as upregulated in P. major including rate limiting genes of MVA (HMGR) and MEP (DXR) pathways and genes (α-AS, BAS, SM, and CYP716) involved in ursolic acid biosynthesis, an important triterpenoid prevalent in Plantago species. The HPLC output further confirmed the higher concentration of ursolic acid in P. major as compared to P. ovata leaf samples, respectively. In addition to terpenoid biosynthesis, KEGG annotation revealed the involvement of differentially expressed unigenes in several metabolic pathways, aminoacyl-tRNA biosynthesis, biosynthesis of antibiotics, and biosynthesis of secondary metabolites. MYB was found as the most abundant transcription factor family in Plantago transcriptome. We have been able to generate valuable information which can help in improving terpenoid production in Plantago. Additionally, the present study has laid a strong foundation for deciphering other important metabolic pathways in Plantago.

In-silico investigation of phytochemicals from Asparagus racemosus as plausible antiviral agent in COVID-19

COVID-19 has ravaged the world and is the greatest of pandemics in human history, in the absence of treatment or vaccine the mortality and morbidity rates are very high. The present investigation was undertaken to screen and identify the potent leads from the Indian Ayurvedic herb, Asparagus racemosus (Willd.) against SARS-CoV-2 using molecular docking and dynamics studies. The docking analysis was performed on the Glide module of Schrödinger suite on two different proteins from SARS-CoV-2 viz. NSP15 Endoribonuclease and spike receptor-binding domain. Asparoside-C, Asparoside-D and Asparoside -F were found to be most effective against both the proteins as confirmed through their docking score and affinity. Further, the 100 ns molecular dynamics study also confirmed the potential of these compounds from reasonably lower root mean square deviations and better stabilization of Asparoside-C and Asparoside-F in spike receptor-binding domain and NSP15 Endoribonuclease respectively. MM-GBSA based binding free energy calculations also suggest the most favourable binding affinities of Asparoside-C and Asparoside-F with binding energies of -62.61 and -55.19 Kcal/mol respectively with spike receptor-binding domain and NSP15 Endoribonuclease. HighlightsAsparagus racemosus have antiviral potentialPhytochemicals of Shatavari showed promising in-silico docking and MD resultsAsparaoside-C and Asparoside-F has good binding with target proteinsAsparagus racemosus holds promise as SARS-COV-2 (S) and (N) proteins inhibitor Communicated by Ramaswamy H. Sarma.

Characterization of MYB35 regulated methyl jasmonate and wound responsive Geraniol 10-hydroxylase-1 gene from Bacopa monnieri

BmG10H-1 transcript from B. monnieri was functionally active. BmG10H-1 promoter drives GUS activity in response to MeJA and wounding. BmMYB35 regulates BmG10H-1 transcript by binding to its promoter. Geraniol 10-hydroxylase (G10H) is one of the important regulatory cytochrome P450 monooxygenase, which is involved in the biosynthesis of monoterpene alkaloids. However, G10H is not characterized at the enzymatic or at the regulatory aspect in B. monnieri. In the present study, we have identified two transcripts of BmG10H (BmG10H-1and BmG10H-2) and characterized the methyl jasmonate (MeJA) and wound responsive BmG10H-1 transcript from B. monnieri. BmG10H-1 showed induced expression after 3 h of MeJA and wounding treatment in the shoot. Yeast purified recombinant BmG10H-1 protein is enzymatically active, having V_max of 0.16 µMsec^-1 μg^-1 protein and catalyzes the hydroxylation of geraniol to 10-hydroxy geraniol. The BmG10H-1 promoter was isolated by using the genome walking method. BmG10H-1 promoter can drive GUS expression in transgenic Arabidopsis thaliana. GUS activity of MeJA and wound-treated Arabidopsis seedlings were found to be increased as compared to the control untreated seedlings, whereas no GUS activity was found in deleted MeJA responsive and W-box cis-elements. This shows that the BmG10H-1 promoter contains functional MeJA (TGACG) and wound responsive (TGACCT) cis-elements. Further, shoot specific and MeJA responsive recombinant BmMYB35 protein was purified, which binds with the MYB recognition cis-element (TGGTTA) present in the BmG10H-1 promoter and transcriptionally activates the reporter gene in yeast. In conclusion, the characterization of MeJA and wound responsive BmG10H-1 provides novel information about its transcriptional regulation by binding with MYB transcription factor in B. monnieri.

Identification of potential anti-TMPRSS2 natural products through homology modelling, virtual screening and molecular dynamics simulation studies

Recent outbreak of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has led to a pandemic of COVID-19. The absence of a therapeutic drug and vaccine is causing severe loss of life and economy worldwide. SARS-CoV and SARS-CoV-2 employ the host cellular serine protease TMPRSS2 for spike (S) protein priming for viral entry into host cells. A potential way to reduce the initial site of SARS-CoV-2 infection may be to inhibit the activity of TMPRSS2. In the current study, the three-dimensional structure of TMPRSS2 was generated by homology modelling and subsequently validated with a number of parameters. The structure-based virtual screening of Selleckchem database was performed through 'Virtual Work Flow' (VSW) to find out potential lead-like TMPRSS2 inhibitors. Camostat and bromhexine are known TMPRSS2 inhibitor drugs, hence these were used as control molecules throughout the study. Based on better dock score, binding-free energy and binding interactions compared to the control molecules, six molecules (Neohesperidin, Myricitrin, Quercitrin, Naringin, Icariin, and Ambroxol) were found to be promising against the TMPRSS2. Binding interactions analysis revealed a number of significant binding interactions with binding site amino residues of TMPRSS2. The all-atoms molecular dynamics (MD) simulation study indicated that all proposed molecules retain inside the receptor in dynamic states. The binding energy calculated from the MD simulation trajectories also favour the strong affinity of the molecules towards the TMPRSS2. Proposed molecules belong to the bioflavonoid class of phytochemicals and are reported to possess antiviral activity, our study indicates their possible potential for application in COVID-19.Communicated by Ramaswamy H. Sarma.