Recent Research Progress in Taxol Biosynthetic Pathway and Acylation Reactions Mediated by Taxus Acyltransferases

Enhancement of paclitaxel production by Neopestalotiopsis vitis via optimization of growth conditions

Accessibility of paclitaxel and other taxoids from natural resources is restricted. Endophytic fungi are novel, rapidly growing resources for producing these compounds. Neopestalotiopsis vitis (N. vitis) has been recently isolated from Corylus avellana, and its ability to produce a variety of taxoids has been detected and confirmed by analytical methods. Simultaneous growth and high production of taxoids by application of different sorts and concentrations of carbon and nitrogen were targeted in the present research. These criteria were assessed in different acidities (pH 4.0-7.0), carbon sources (sucrose, fructose, glucose, mannitol, sorbitol, and malt extract), and nitrogen forms (urea, ammonium nitrate, potassium nitrate, ammonium phosphate, and ammonium sulfate) by testing one parameter at a time approach. The first analysis introduced pH 7.0 as the best acidity of the medium for N. vitis, where the highest paclitaxel yield was generated. Further analysis introduced 3% Malt extract as the best carbon-providing medium. In the next step, the effects of nitrogen forms on the growth rate, paclitaxel yield, alkaloids, and amino acid contents were evaluated. Based on the results of this experiment, 5 mM ammonium sulfate was selected as the best nitrogen source to obtain the maximum biomass and paclitaxel yield. Overall, the results introduce a medium containing 3% (w/v) malt extract and 5 mM ammonium sulfate at pH 7.0 as the best medium in which N. vitis produces the highest paclitaxel yield coincident with rapid and sustainable growth. The findings pave the way for industrial manufacturing of taxoids.

Paclitaxel production from endophytic Mucor circinelloides isolated from Taxus sp. of the Northern Himalayan region

The current investigation involved the isolation of 13 endophytic fungi from Taxus sp. collected in Himachal Pradesh, India. Among these, isolate PAT-3 produced 195.13 mg/L of Taxol in reformative medium broth using microbial fermentation as an alternative source. The PAT-3 isolate was characterized as Mucor circinelloides through morphologic and molecular techniques. The PAT-3 isolate was the only one to exhibit positive results for the Taxol biosynthesis-related genes 10-deacetylbaccatin-III-10-O-acetyltransferase (dbat), Baccatin-III, 3: amino, 3 phenylpropanol transferase (bapt), and taxadienol-acetyltransferase (tat). Furthermore, human breast cancer (MCF-7) and human melanoma cancer (SKMEL-28) cell lines demonstrated the cytotoxicity of Taxol extracted from isolate PAT-3, with IC50 values of 80.32 µg/mL and 77.21 µg/mL, respectively. To our knowledge, this is the first study that demonstrates the ability of the endophytic fungus M. circinelloides from Taxus sp. in the northern Himalayan region to produce paclitaxel. The study's findings show that Mucor circinelloides is an excellent alternative source of Taxol, and they may pave the way for the production of Taxol at the industrial level in future.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-024-04091-7.

Engineering cyanobacteria as a new platform for producing taxol precursors directly from carbon dioxide

Taxol serves as an efficient natural anticancer agent with extensive applications in the treatment of diverse malignancies. Although advances in synthetic biology have enabled the de novo synthesis of taxol precursors in various microbial chassis, the total biosynthesis of taxol remains challengable owing to the restricted oxidation efficiency in heterotrophic microbes. Here, we engineered Synechocystis sp. PCC 6803 with modular metabolic pathways consisting of the methylerythritol phosphate pathway enzymes and taxol biosynthetic enzymes for production of taxadiene-5α-ol (T5α-ol), the key oxygenated intermediate of taxol. The best strain DIGT-P560 produced up to 17.43 mg/L of oxygenated taxanes and 4.32 mg/L of T5α-ol. Moreover, transcriptomic analysis of DIGT-P560 revealed that establishing a oxygenated taxane flux may enhance photosynthetic electron transfer efficiency and central metabolism in the engineered strain to ameliorate the metabolic disturbances triggered by the incorporation of exogenous genes. This is the first demonstration of photosynthetic production of taxadiene-5α-ol from CO2 in cyanobacteria, highlighting the broad prospects of engineered cyanobacteria as bio-solar cell factories for valuable terpenoids production and expanding the ideas for further rational engineering and optimization.

Unraveling the key step in the aroma puzzle: Insights into alcohol acyltransferases in strawberries

Alcohol acyltransferases (AATs) play a crucial role in catalyzing the transfer of acyl groups, contributing to the diverse aroma of fruits, including strawberries. In this research we identified nine AAT genes in strawberries through a comprehensive analysis involving phylogenetics, gene structure, conserved motifs, and structural protein model examinations. The study used the 'Camarosa' strawberry genome database, and experiments were conducted with fruits harvested at different developmental and ripening stages. The transcriptional analysis revealed differential expression patterns among the AAT genes during fruit ripening, with only four genes (SAAT, FaAAT2, FaAAT7, and FaAAT9) showing increased transcript accumulation correlated with total AAT enzyme activity. Additionally, the study employed in silico methods, including sequence alignment, phylogenetic analysis, and structural modeling, to gain insights into the AAT protein model structures with increase expression pattern during fruit ripening. The four modeled AAT proteins exhibited structural similarities, including conserved catalytic sites and solvent channels. Furthermore, the research investigated the interaction of AAT proteins with different substrates, highlighting the enzymes' promiscuity in substrate preferences. The study contributes with valuable information to unveil AAT gene family members in strawberries, providing scientific background for further exploration of their biological characteristics and their role in aroma biosynthesis during fruit ripening.

Genome-Wide Identification and Expression Pattern Analysis of BAHD Acyltransferase Family in Taxus mairei

BAHD acyltransferases are involved in catalyzing and regulating the secondary metabolism in plants. Despite this, the members of BAHD family and their functions have not been reported in the Taxus species. In this study, a total of 123 TwBAHD acyltransferases from Taxus wallichiana var. mairei genome were identified and divided into six clades based on phylogenetic analysis, of which Clade VI contained a Taxus-specific branch of 52 members potentially involved in taxol biosynthesis. Most TwBAHDs from the same clade shared similar conserved motifs and gene structures. Besides the typical conserved motifs within the BAHD family, the YPLAGR motif was also conserved in multiple clades of T. mairei. Moreover, only one pair of tandem duplicate genes was found on chromosome 1, with a Ka/Ks ratio < 1, indicating that the function of duplicate genes did not differentiate significantly. RNA-seq analysis revealed different expression patterns of TwBAHDs in MeJA induction and tissue-specific expression experiments. Several TwBAHD genes in the Taxus-specific branch were highly expressed in different tissues of T. mairei, suggesting an important role in the taxol pathway. This study provides comprehensive information for the TwBAHD gene family and sets up a basis for its potential functions.

Characterization and heterologous reconstitution of Taxus biosynthetic enzymes leading to baccatin III

Paclitaxel is a well known anticancer compound. Its biosynthesis involves the formation of a highly functionalized diterpenoid core skeleton (baccatin III) and the subsequent assembly of a phenylisoserinoyl side chain. Despite intensive investigation for half a century, the complete biosynthetic pathway of baccatin III remains unknown. In this work, we identified a bifunctional cytochrome P450 enzyme [taxane oxetanase 1 (TOT1)] in Taxus mairei that catalyzes an oxidative rearrangement in paclitaxel oxetane formation, which represents a previously unknown enzyme mechanism for oxetane ring formation. We created a screening strategy based on the taxusin biosynthesis pathway and uncovered the enzyme responsible for the taxane oxidation of the C9 position (T9αH1). Finally, we artificially reconstituted a biosynthetic pathway for the production of baccatin III in tobacco.

Identification and Functional Characterization of a Novel Sinapyl Alcohol Acyltransferase from Euphorbia lathyris L

Methoxyeugenol is a phenylpropene compound derived from plants and has various bioactivities. The chemical synthesis of methoxyeugenol is accompanied by pollution issues, whereas extraction from plants is associated with problems such as low yield and high cost. The production of methoxyeugenol can be effectively addressed through an enzymatic approach. In this study, the acyltransferase genes of Euphorbia lathyris L. were screened by homologous alignment of the transcriptome data of E. lathyris in the late growth stage and the acyltransferase genes of the closely related plant species. The results showed that ElBAHD10 had the closest relationship with earlier reported ScCFAT and PhCFAT, which were found to catalyze the reaction of coniferyl alcohol to generate coniferyl acetate. The ElBAHD10 gene was successfully cloned from E. lathyris and subsequently expressed in Escherichia coli. The purified protein ElBAHD10 catalyzed the reaction of sinapyl alcohol with acetyl CoA and cinnamoyl CoA to form sinapyl acetate and sinapyl cinnamate, respectively. In contrast, the crude ElBAHD10 protein could catalyze sinapyl alcohol to directly generate methoxyeugenol. The recombinant E. coli strain expressing ElBAHD10 produced methoxyeugenol through whole-cell transformation. This study provides insights and lays the foundation for methoxyeugenol production through biosynthetic approaches.

Research Advances in Clinical Applications, Anticancer Mechanism, Total Chemical Synthesis, Semi-Synthesis and Biosynthesis of Paclitaxel

Paclitaxel, a natural secondary metabolite isolated and purified from the bark of the Taxus tree, is considered one of the most successful natural anticancer drugs due to its low toxicity, high potency and broad-spectrum anticancer activity. Taxus trees are scarce and slow-growing, and with extremely low paclitaxel content, the contradiction between supply and demand in the market is becoming more and more intense. Therefore, researchers have tried to obtain paclitaxel by various methods such as chemical synthesis, artificial culture, microbial fermentation and tissue cell culture to meet the clinical demand for this drug. This paper provides a comprehensive overview of paclitaxel extraction, combination therapy, total synthesis, semi-synthesis and biosynthesis in recent years and provides an outlook, aiming to provide a theoretical basis and reference for further research on the production and application of paclitaxel in the future.

Family characteristics, phylogenetic reconstruction, and potential applications of the plant BAHD acyltransferase family

The BAHD acyltransferase family is a class of proteins in plants that can acylate a variety of primary and specialized secondary metabolites. The typically acylated products have greatly improved stability, lipid solubility, and bioavailability and thus show significant differences in their physicochemical properties and pharmacological activities. Here, we review the protein structure, catalytic mechanism, and phylogenetic reconstruction of plant BAHD acyltransferases to describe their family characteristics, acylation reactions, and the processes of potential functional differentiation. Moreover, the potential applications of the BAHD family in human activities are discussed from the perspectives of improving the quality of economic plants, enhancing the efficacy of medicinal plants, improving plant biomass for use in biofuel, and promoting stress resistance of land plants. This review provides a reference for the research and production of plant BAHD acyltransferases.

Differential RNA-Seq Analysis Predicts Genes Related to Terpene Tailoring in Caryopteris × clandonensis

Enzymatic terpene functionalization is an essential part of plant secondary metabolite diversity. Within this, multiple terpene-modifying enzymes are required to enable the chemical diversity of volatile compounds essential in plant communication and defense. This work sheds light on the differentially transcribed genes within Caryopteris × clandonensis that are capable of functionalizing cyclic terpene scaffolds, which are the product of terpene cyclase action. The available genomic reference was subjected to further improvements to provide a comprehensive basis, where the number of contigs was minimized. RNA-Seq data of six cultivars, Dark Knight, Grand Bleu, Good as Gold, Hint of Gold, Pink Perfection, and Sunny Blue, were mapped on the reference, and their distinct transcription profile investigated. Within this data resource, we detected interesting variations and additionally genes with high and low transcript abundancies in leaves of Caryopteris × clandonensis related to terpene functionalization. As previously described, different cultivars vary in their modification of monoterpenes, especially limonene, resulting in different limonene-derived molecules. This study focuses on predicting the cytochrome p450 enzymes underlying this varied transcription pattern between investigated samples. Thus, making them a reasonable explanation for terpenoid differences between these plants. Furthermore, these data provide the basis for functional assays and the verification of putative enzyme activities.

Biosynthesis and the Transcriptional Regulation of Terpenoids in Tea Plants (Camellia sinensis)

Terpenes, especially volatile terpenes, are important components of tea aroma due to their unique scents. They are also widely used in the cosmetic and medical industries. In addition, terpene emission can be induced by herbivory, wounding, light, low temperature, and other stress conditions, leading to plant defense responses and plant-plant interactions. The transcriptional levels of important core genes (including HMGR, DXS, and TPS) involved in terpenoid biosynthesis are up- or downregulated by the MYB, MYC, NAC, ERF, WRKY, and bHLH transcription factors. These regulators can bind to corresponding cis-elements in the promoter regions of the corresponding genes, and some of them interact with other transcription factors to form a complex. Recently, several key terpene synthesis genes and important transcription factors involved in terpene biosynthesis have been isolated and functionally identified from tea plants. In this work, we focus on the research progress on the transcriptional regulation of terpenes in tea plants (Camellia sinensis) and thoroughly detail the biosynthesis of terpene compounds, the terpene biosynthesis-related genes, the transcription factors involved in terpene biosynthesis, and their importance. Furthermore, we review the potential strategies used in studying the specific transcriptional regulation functions of candidate transcription factors that have been discriminated to date.

Comparative Genome-Wide Analysis of Two Caryopteris x Clandonensis Cultivars: Insights on the Biosynthesis of Volatile Terpenoids

Caryopteris x Clandonensis, also known as bluebeard, is an ornamental plant containing a large variety of terpenes and terpene-like compounds. Four different cultivars were subjected to a principal component analysis to elucidate variations in terpenoid-biosynthesis and consequently, two representative cultivars were sequenced on a genomic level. Functional annotation of genes as well as comparative genome analysis on long read datasets enabled the identification of cultivar-specific terpene synthase and cytochrome p450 enzyme sequences. This enables new insights, especially since terpenoids in research and industry are gaining increasing interest due to their importance in areas such as food preservation, fragrances, or as active ingredients in pharmaceutical formulations. According to BUSCO assessments, the presented genomes have an average size of 355 Mb and about 96.8% completeness. An average of 52,090 genes could be annotated as putative proteins, whereas about 42 were associated with terpene synthases and about 1340 with cytochrome p450 enzymes.

Influence of Long-Term Agar-Slant Preservation at 4 °C on the Recombinant Enzyme Activity of Engineered Yeast

Strain preservation to maintain stable vitality and the recombinant enzyme activity plays a crucial role in industrial fermentation. A Pichia pastoris strain is routinely stored at −80 °C in a glycerol vial and activated on an antibiotic-containing YPD agar plate before being used for fermentation. Alternatively, the activated strain should be preserved in the agar slant at 2~4 °C (low-temperature storage) for a short period before use. To maximize the utilization of the low-temperature storage for fermentation, we evaluated this method by observing the capacity of both the vitality and the recombinant enzyme activity of the strain at different preservation durations. We found that engineered yeast could be preserved by low-temperature storage for at least 30 months without losing its vitality and biomass enzyme activity by the end of fermentation and could be directly used for the seed cultivation of fermentation, which is more time-saving than strain recovery from −80 °C in a glycerol vial. Moreover, the antibiotic added to the agar slant could be omitted if the heterologous gene was integrated into the host chromosome. Our approach may greatly elevate the production efficiency of the strain.

Transcription level differences in Taxus wallichiana var. mairei elicited by Ce3+, Ce4+ and methyl jasmonate

Taxol is a precious and effective anticancer drug. Cerium and methyl jasmonate (MJ) have been shown to increase the yield of taxol in taxus cells. However, the mechanisms of cerium-mediated and MJ-mediated taxol biosynthesis remain unknown. RNA-Seq was applied to study the overall regulation mechanism of cerium and MJ on taxol biosynthesis and analyze the differences among T. mairei cells elicited by Ce³⁺, Ce⁴⁺ and MJ on transcriptional level . Using sequence homology, 179 unigenes were identified as taxol synthesis genes. Under the condition of 100 μM MJ, taxol synthesis genes were up-regulated. Notably, taxol synthesis genes were down-regulated expression at 1 mM Ce³⁺ and 1 mM Ce⁴⁺. Differential expression genes involved in some related functions were analyzed, such as MAPK signaling pathway and plant-pathogen interaction. Sequence alignment and phylogenetic analysis of nine differentially expressed WRKYs in our data were carried out.

Separation and Purification of Taxanes from Crude Taxus cuspidata Extract by Antisolvent Recrystallization Method

Taxanes are natural compounds with strong antitumor activity. In this study, we first enriched taxanes by ultrasonic extraction and liquid–liquid extraction from Taxus cuspidata, then purified these taxanes by the antisolvent recrystallization method, and discussed the effects of four recrystallization conditions on the purity of eight target compounds. The most promising purification results were obtained using methanol as a solvent and water as an antisolvent. Response surface methodology (RSM) was used to further optimize the optimal purification conditions: when the crude extraction concentration was 555.28 mg/mL, an antisolvent to solvent volume ratio was 28.16 times, the deposition temperature was 22.91 °C, and the deposition time was 1.76 min, the purity of the taxanes reached its maximum. The scanning electron microscopy (SEM) results showed that recrystallization could effectively reduce the particle size of crude Taxus cuspidata and control the particle morphology. X-ray diffraction (XRD) and Raman spectrum experiments demonstrated that the amorphous state of the crude Taxus cuspidata did not change during the recrystallization process, and always remained amorphous. This recrystallization method can effectively improve the purity of taxanes in Taxus cuspidata, and is suitable for the preliminary purification of taxanes.