Genome-wide detection of terpene synthase genes in holy basil (Ocimum sanctum L.)

Chromosome-level genome and multi-omics analyses provide insights into the geo-herbalism properties of Alpinia oxyphylla

Introduction

Alpinia oxyphylla Miquel (A. oxyphylla), one of the "Four Famous South Medicines" in China, is an essential understory cash crop that is planted widely in the Hainan, Guangdong, Guangxi, and Fujian provinces. Particularly, A. oxyphylla from Hainan province is highly valued as the best national product for geo-herbalism and is an important indicator of traditional Chinese medicine efficacy. However, the molecular mechanism underlying the formation of its quality remains unspecified.

Methods

To this end, we employed a multi-omics approach to investigate the authentic quality formation of A. oxyphylla.

Results

In this study, we present a high-quality chromosome-level genome assembly of A. oxyphylla, with contig N50 of 76.96 Mb and a size of approximately 2.08Gb. A total of 38,178 genes were annotated, and the long terminal repeats were found to have a high frequency of 61.70%. Phylogenetic analysis demonstrated a recent whole-genome duplication event (WGD), which occurred before A. oxyphylla's divergence from W. villosa (~14 Mya) and is shared by other species from the Zingiberaceae family (Ks, ~0.3; 4DTv, ~0.125). Further, 17 regions from four provinces were comprehensively assessed for their metabolite content, and the quality of these four regions varied significantly. Finally, genomic, metabolic, and transcriptomic analyses undertaken on these regions revealed that the content of nootkatone in Hainan was significantly different from that in other provinces.

Discussion

Overall, our findings provide novel insights into germplasm conservation, geo-herbalism evaluation, and functional genomic research for the medicinal plant A. oxyphylla.

Genome-wide identification and expression analysis of terpene synthases in Gossypium species in response to gossypol biosynthesis

Cottonseed is an invaluable resource, providing protein, oil, and abundant minerals that significantly contribute to the well-being and nutritional needs of both humans and livestock. However, cottonseed also contains a toxic substance called gossypol, a secondary metabolite in Gossypium species that plays an important role in cotton plant development and self-protection. Herein, genome-wide analysis and characterization of the terpene synthase (TPS) gene family identified 304 TPS genes in Gossypium. Bioinformatics analysis revealed that the gene family was grouped into six subgroups TPS-a, TPS-b, TPS-c, TPS-e, TPS-f, and TPS-g. Whole-genome, segmental, and tandem duplication contributed to the evolution of TPS genes. According to the analysis of selection pressure, it was predicted that TPS genes experience predominantly negative selection, with positive selection occurring subsequently. RT-qPCR analysis in TM-1 and CRI-12 lines revealed GhTPS48 gene as the candidate gene for silencing experiments. To summarize, comprehensive genome-wide studies, RT-qPCR, and gene silencing experiments have collectively demonstrated the involvement of the TPS gene family in the biosynthesis of gossypol in cotton.

Monoterpene synthases of three closely related sage species (Salvia officinalis, S. fruticosa and S. pomifera, Lamiaceae)

The diversity of plant monoterpenes is largely based on the catalytic activity of monoterpene synthases. Additionally, copy number variation of monoterpene synthase genes may contribute to the quantity of transcripts and hence to the essential oil profile. This study used whole-genome sequencing and digital PCR for the measurement of copy number variation and quantification of gene expression in three closely related Salvia species, namely Salvia officinalis, Salvia pomifera and Salvia fruticosa. Twelve, 13 and 15 monoterpene synthase-encoding open-reading frames were predicted for Salvia officinalis, Salvia pomifera and Salvia fruticosa, respectively. In Salvia officinalis, one of the open reading frames was disrupted indicating a pseudogene. Monoterpene synthase genes were generally single copy per haploid genome, only a few were double or triple copy genes. Expression levels of monoterpene synthases in leaves corresponded generally well with essential oil composition. In some cases, a higher expression level of a certain monoterpene synthase could be explained by its duplication or triplication. The very high content of thujones in Salvia pomifera, for example, was accompanied by gene duplication and increased gene expression of (+)-sabinene synthase responsible for the thujone precursor sabinene. In Salvia officinalis, three individuals different in their essential oil profile showed significant differences in their monoterpene synthase expression levels corresponding roughly to the profile of the essential oils. Transcript expression of monoterpene synthase genes were measured in leaf, calyx and corolla. The corolla differed significantly from leaves, while calyces usually showed a profile intermediary between leaf and corolla.

Full-length transcriptome analysis of two chemotype and functional characterization of genes related to sesquiterpene biosynthesis in Atractylodes lancea

Atractylodes lancea (Thunb.) DC. is an important medicinal plant mainly distributed in China. A. lancea is rich in volatile oils and has a significant effect on various diseases, including coronavirus disease 2019 (COVID-19). Based on the signature constituents of volatile oils, A. lancea is divided into two chemotypes: the Dabieshan and Maoshan chemotype. Gas chromatography-mass spectrometry (GC-MS) results revealed that the hinesol and β-eudesmol contents in the Dabieshan chemotype were higher than those in the Maoshan chemotype. Next-generation sequencing (NGS) and single-molecule real-time (SMRT) sequencing technologies were combined to investigate the molecular mechanisms of sesquiterpenoid biosynthesis in A. lancea. A total of 42 differentially expressed genes (DEGs) for terpenoid biosynthesis were identified in the two chemotype groups, and nine full-length terpene synthase (TPS) genes were identified. Subcellular localization revealed that AlTPS1 and AlTPS2 proteins were localized in the nucleus and endoplasmic reticulum. They use FPP as a substrate to generate sesquiterpenoids. AlTPS1 catalyzes biosynthesis of elemol while AlTPS2 is observed to perform β-farnesene synthase activity. This study provides information for understanding the differences in the accumulation of terpenoids in two chemotypes of A. lancea and lays a foundation for further elucidation of the molecular mechanism of sesquiterpenoid biosynthesis.

From Genome Mining to Protein Engineering: A Structural Bioinformatics Route

This chapter outlines applications in genome mining, along with computational methods to predict protein structure and protein-ligand docking. It offers a simple computational route to rapidly identify proteins of interest from genomic and proteomic data, to accurately predict their three-dimensional structures, and to dock small molecules to their binding pockets and strategies to improve their biophysical properties depending on the needs of the experimental researcher.

Chromosome-level genome assembly and functional characterization of terpene synthases provide insights into the volatile terpenoid biosynthesis of Wurfbainia villosa

Wurfbainia villosa is a well-known medicinal and edible plant that is widely cultivated in the Lingnan region of China. Its dried fruits (called Fructus Amomi) are broadly used in traditional Chinese medicine for curing gastrointestinal diseases and are rich in volatile terpenoids. Here, we report a high-quality chromosome-level genome assembly of W. villosa with a total size of approximately 2.80 Gb, 42 588 protein-coding genes, and a very high percentage of repetitive sequences (87.23%). Genome analysis showed that W. villosa likely experienced a recent whole-genome duplication event prior to the W. villosa-Zingiber officinale divergence (approximately 11 million years ago), and a recent burst of long terminal repeat insertions afterward. The W. villosa genome enabled the identification of 17 genes involved in the terpenoid skeleton biosynthesis pathway and 66 terpene synthase (TPS) genes. We found that tandem duplication events have an important contribution to the expansion of WvTPSs, which likely drove the production of volatile terpenoids. In addition, functional characterization of 18 WvTPSs, focusing on the TPS-a and TPS-b subfamilies, showed that most of these WvTPSs are multi-product TPS and are predominantly expressed in seeds. The present study provides insights into the genome evolution and the molecular basis of the volatile terpenoids diversity in W. villosa. The genome sequence also represents valuable resources for the functional gene research and molecular breeding of W. villosa.

Genome-wide analysis of terpene synthase gene family to explore candidate genes related to disease resistance in Prunus persica

In plants, a family of terpene synthases (TPSs) is responsible for the biosynthesis of terpenes and contributes to species-specific diversity of volatile organic compounds, which play essential roles in fitness of plants. However, little is known about the TPS gene family in peach and/or nectarine (Prunus persica L.). In this study, we identified 40 PpTPS genes in peach genome v2.0. Although these PpTPSs could be clustered into five classes, they distribute in several gene clusters of three chromosomes, share conserved exon-intron organizations, and code similar protein motifs. Thirty-five PpTPSs, especially PpTPS2, PpTPS23, PpTPS17, PpTPS18, and PpTPS19, altered their transcript levels after inoculation with Botryosphaeria dothidea, a cause of peach gummosis, compared to the mock treatments, which might further affect the contents of 133 terpenoids at 48 hours and/or 84 hours post inoculations in the current-year shoots of 'Huyou018', a highly susceptible nectarine cultivar. Moreover, about fifteen PpTPSs, such as PpTPS1, PpTPS2, PpTPS3, and PpTPS5, showed distinct expression patterns during fruit development and ripening in two peach cultivars, yellow-fleshed 'Jinchun' and white-fleshed 'Hikawa Hakuho'. Among them, the transcription level of chloroplast-localized PpTPS3 was obviously related to the content of linalool in fruit pulps. In addition, elevated concentrations (0.1 g/L to 1.0 g/L) of linalool showed antifungal activities in PDA medium. These results improve our understanding of peach PpTPS genes and their potential roles in defense responses against pathogens.

Physiological responses and variation in secondary metabolite content among Thai holy basil cultivars (Ocimum tenuiflorum L.) grown under controlled environmental conditions in a plant factory

Holy basil (Ocimum Tenuiflorum L.) is a widely used herb containing several bioactive compounds of interest for the food and pharmaceutical industries. Plant factories using artificial lighting (PFAL) is a modern agricultural system that offers opportunity to improve crop production and stabilizes productivity in many herbal plants. However, little is known about the variation among holy basil varieties that can be cultivated and provide reasonable biomass and bioactive compounds in PFAL. We therefore evaluated 10 Thai accessions and two commercial cultivars in a PFAL (with hydroponic cultivation) to categorize cultivar characteristics by investigating physiological responses and secondary metabolite variation at plant flowering stage. Among Thai varieties, net photosynthetic rate (Pn) was significantly highest in varieties OC059 and OC081. The greatest growth and biomass measures were observed in OC064. Antioxidant capacity also varied, with the greatest accumulation of total phenolic compounds (TPC), flavonoids, and antioxidant activity by DPPH assay in OC064, and highest terpenoid content in OC194. The accumulation of major compounds confirmed by showing the highest levels of eugenol in OC057, OC063, OC194, and OC195 and methyl eugenol in OC072 and OC081. The highest α-humulene content was found in OC059. PCA based on physiological responses and secondary metabolites indicate that OC064 was clearly distinguished from other cultivars/accessions. These findings demonstrate variation across holy basil accessions for physiologic responses, antioxidant capacity, and secondary compounds in PFAL. These insights lead to identification of suitable varieties which is the most important step of developing an efficient method for producing high quality raw materials of Thai holy basil for supplying the foods and pharmaceutical industries.

Comparative Transcriptome Analysis Reveals Coordinated Transcriptional Regulation of Central and Secondary Metabolism in the Trichomes of Cannabis Cultivars

Cannabis is one of the few plant genera capable of producing cannabinoids, the effects of which are synergized by terpene interactions. As the biosynthesis of both metabolite classes requires the same intracellular feedstocks, this work describes the coordinated regulation of global metabolic pathways that allows for their joint copious production in vivo. To this end, a transcriptomics-based approach to characterize the glandular trichomes of five Cannabis cultivars was pursued. Besides revealing metabolic traits that enhanced and proportionated the supply of critical carbon precursors, in-depth analysis showed significantly increased gene expression of two particular enzymes to meet the huge nicotinamide adenine dinucleotide phosphate (NADPH) demand of secondary metabolite production. Furthermore, it led to a hypothesis that the methyl-d-erythritol 4-phosphate pathway might be utilized more than the mevalonic acid pathway in Cannabis trichomes. While both pathways were found to be activated in a modular and calibrated way that reflected their broad participation in physiological processes, the genes for hexanoate, cannabinoid, and terpene biosynthesis were, in contrast, up-regulated in an en bloc and multi-loci manner due to their specific roles in secondary metabolite production. In addition, three new terpene synthases were characterized based on both in silico and experimental assays. Altogether, the study enhances the current understanding of secondary metabolite production in Cannabis cultivars, which may assist in their characterization and development.

Identification and Characterization of Bifunctional Drimenol Synthases of Marine Bacterial Origin

Natural drimane-type sesquiterpenes, including drimenol, display diverse biological activities. These active compounds are distributed in plants and fungi; however, their accumulation in bacteria remains unknown. Consequently, bacterial drimane-type sesquiterpene synthases remain to be characterized. Here, we report five drimenol synthases (DMSs) of marine bacterial origin, all belonging to the haloacid dehalogenase (HAD)-like hydrolase superfamily with the conserved DDxxE motif typical of class I terpene synthases and the DxDTT motif found in class II diterpene synthases. They catalyze two continuous reactions: the cyclization of farnesyl pyrophosphate (FPP) into drimenyl pyrophosphate and dephosphorylation of drimenyl pyrophosphate into drimenol. Protein structure modeling of the characterized Aquimarina spongiae DMS (AsDMS) suggests that the FPP substrate is located within the interdomain created by the DDxxE motif of N-domain and DxDTT motif of C-domain. Biochemical analysis revealed two aspartate residues of the DDxxE motif that might contribute to the capture of the pyrophosphate moiety of FPP inside the catalytic site of AsDMS, which is essential for efficient cyclization and subsequent dephosphorylation reactions. The middle aspartate residue of the DxDTT motif is also critical for cyclization. Thus, AsDMS utilizes both motifs in the reactions. Remarkably, the unique protein architecture of AsDMS, which is characterized by the fusion of a HAD-like domain (N-domain) and a terpene synthase β domain (C-domain), significantly differentiates this new enzyme. Our findings of the first examples of bacterial DMSs suggest the biosynthesis of drimane sesquiterpenes in bacteria and shed light on the divergence of the structures and functions of terpene synthases.

Genomic Analysis Based on Chromosome-Level Genome Assembly Reveals an Expansion of Terpene Biosynthesis of Azadirachta indica

Azadirachta indica (neem), an evergreen tree of the Meliaceae family, is a source of the potent biopesticide azadirachtin. The lack of a chromosome-level assembly impedes an in-depth understanding of its genome architecture and the comparative genomic analysis of A. indica. Here, a high-quality genome assembly of A. indica was constructed using a combination of data from Illumina, PacBio, and Hi-C technology, which is the first chromosome-scale genome assembly of A. indica. Based on the length of our assembly, the genome size of A. indica is estimated to be 281 Mb anchored to 14 chromosomes (contig N50 = 6 Mb and scaffold N50 = 19 Mb). The genome assembly contained 115 Mb repetitive elements and 25,767 protein-coding genes. Evolutional analysis revealed that A. indica didn't experience any whole-genome duplication (WGD) event after the core eudicot γ event, but some genes and genome segment might likely experienced recent duplications. The secondary metabolite clusters, TPS genes, and CYP genes were also identified. Comparative genomic analysis revealed that most of the A. indica-specific TPS genes and CYP genes were located on the terpene-related clusters on chromosome 13. It is suggested that chromosome 13 may play an important role in the specific terpene biosynthesis of A. indica. The gene duplication events may be responsible for the terpene biosynthesis expansion in A. indica. The genomic dataset and genomic analysis created for A. indica will shed light on terpene biosynthesis in A. indica and facilitate comparative genomic research of the family Meliaceae.

Diversity and Functional Evolution of Terpene Synthases in Rosaceae

Terpenes are organic compounds and play important roles in plant development and stress response. Terpene synthases (TPSs) are the key enzymes for the biosynthesis of terpenes. For Rosaceae species, terpene composition represents a critical quality attribute, but limited information is available regarding the evolution and expansion occurring in the terpene synthases gene family. Here, we selected eight Rosaceae species with sequenced and annotated genomes for the identification of TPSs, including three Prunoideae, three Maloideae, and two Rosoideae species. Our data showed that the TPS gene family in the Rosaceae species displayed a diversity of family numbers and functions among different subfamilies. Lineage and species-specific expansion of the TPSs accompanied by frequent domain loss was widely observed within different TPS clades, which might have contributed to speciation or environmental adaptation in Rosaceae. In contrast to Maloideae and Rosoideae species, Prunoideae species owned less TPSs, with the evolution of Prunoideae species, TPSs were expanded in modern peach. Both tandem and segmental duplication significantly contributed to TPSs expansion. Ka/Ks calculations revealed that TPSs genes mainly evolved under purifying selection except for several pairs, where the divergent time indicated TPS-e clade was diverged relatively anciently. Gene function classification of TPSs further demonstrated the function diversity among clades and species. Moreover, based on already published RNA-Seq data from NCBI, the expression of most TPSs in Malus domestica, Prunus persica, and Fragaria vesca displayed tissue specificity and distinct expression patterns either in tissues or expression abundance between species and TPS clades. Certain putative TPS-like proteins lacking both domains were detected to be highly expressed, indicating the underlying functional or regulatory potentials. The result provided insight into the TPS family evolution and genetic information that would help to improve Rosaceae species quality.

Systematic identification of Ocimum sanctum sesquiterpenoid synthases and (-)-eremophilene overproduction in engineered yeast

Plant-derived natural active products have attracted increasing attention for use in flavors and perfumes. These compounds also have applications in insect pest control because of their environment-friendly properties. Holy basil (Ocimum sanctum), a famous herb used in Ayurveda in India, is a natural source of medical healing agents and insecticidal repellents. Despite the available genomic sequences and genome-wide bioinformatic analysis of terpene synthase genes, the functionality of the sesquiterpene genes involved in the unique fragrance and insecticidal activities of Holy basil are largely unknown. In this study, we systematically screened the sesquiterpenoid biosynthesis genes in this plant using a precursor-providing yeast system. The enzymes that synthesize β-caryophyllene and its close isomer α-humulene were successfully identified. The enzymatic product of OsaTPS07 was characterized by in vivo mining, in vitro reaction, and NMR detection. This product was revealed as (-)-eremophilene. We created a mutant yeast strain that can achieve a high-yield titer by adjusting the gene copy number and FPP precursor enhancement. An optimized two-stage fed-batch fermentation method achieved high biosynthetic capacity, with a titer of 34.6 g/L cyclic sesquiterpene bioproduction in a 15-L bioreactor. Further insect-repelling assays demonstrated that (-)-eremophilene repelled the insect pest, fall leafworm, suggesting the potential of (-)-eremophilene as an alternative to synthetic chemicals for agricultural pest control. This study highlights the potential of our microbial platform for the bulk mining of plant-derived ingredients and provides an impressive cornerstone for their industrial utilization.

Synthesis of flavour-related linalool is regulated by PpbHLH1 and associated with changes in DNA methylation during peach fruit ripening

Linalool is one of the common flavour-related volatiles across the plant kingdom and plays an essential role in determining consumer liking of plant foods. Although great process has been made in identifying terpene synthase (TPS) genes associated with linalool synthesis, much less is known about regulation of this pathway. We initiated study by identifying PpTPS3 encoding protein catalysing enantiomer (S)-(+)-linalool synthesis, which is a major linalool component (˜70%) observed in ripe peach fruit. Overexpression of PpTPS3 led to linalool accumulation, while virus-induced gene silencing of PpTPS3 led to a 66.5% reduction in linalool content in peach fruit. We next identified transcription factor (TF) PpbHLH1 directly binds to E-box (CACATG) in the PpTPS3 promoter and activates its expression based on yeast one-hybrid assay and EMSA analysis. Significantly positive correlation was also observed between PpbHLH1 expression and linalool production across peach cultivars. Peach fruit accumulated more linalool after overexpressing PpbHLH1 in peach fruit and reduced approximately 54.4% linalool production after silencing this TF. DNA methylation analysis showed increased PpTPS3 expression was associated with decreased 5 mC level in its promoter during peach fruit ripening, but no reverse pattern was observed for PpbHLH1. Arabidopsis and tomato fruits transgenic for peach PpbHLH1 synthesize and accumulate higher levels of linalool compared with wild-type controls. Taken together, these results would greatly facilitate efforts to enhance linalool production and thus improve flavour of fruits.

Genome-wide detection and classification of terpene synthase genes in Aquilaria agallochum

Agarwood, one of the precious woods in the globe, is produced by Aquilaria plant species during an upshot of wounding and infection. Produced as a defence response, the dark, fragrant resin gets secreted in the plant's duramen, which is impregnated with fragrant molecules with the due course. Agarwood has gained worldwide popularity due to its high aromatic oil, fragrance, and pharmaceutical value, which makes it highly solicited by numerous industries. Predominant chemical constituents of agarwood, sesquiterpenoids, and 2-(2-phenylethyl) chromones have been scrutinized to comprehend the scientific nature of the fragrant wood and develop novel products. However, the genes involved in the biosynthesis of these aromatic compounds are still not comprehensively studied in Aquilaria. In this study, publicly available genomic and transcriptomics data of Aquilaria agallochum were integrated to identify putative functional terpene synthase genes (TPSs). The in silico study enabled us to identify ninety-six TPSs, of which thirty-nine full-length genes were systematically classified into TPS-a, TPS-b, TPS-c, TPS-e, TPS-f, and TPS-g subfamilies based on their gene structure, conserve motif, and phylogenetic comparison with TPSs from other plant species. Analysis of the cis-regulatory elements present upstream of AaTPSs revealed their association with hormone, stress and light responses. In silico expression studies detected their up-regulation in stress induced tissue. This study provides a basic understanding of terpene synthase gene repertoire in Aquilaria agallochum and unlatches opportunities for the biochemical characterization and biotechnological exploration of these genes.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12298-021-01040-z.

Adaptive and nonadaptive causes of heterogeneity in genetic differentiation across the Mimulus guttatus genome

Genetic diversity becomes structured among populations over time due to genetic drift and divergent selection. Although population structure is often treated as a uniform underlying factor, recent resequencing studies of wild populations have demonstrated that diversity in many regions of the genome may be structured quite dissimilar to the genome-wide pattern. Here, we explored the adaptive and nonadaptive causes of such genomic heterogeneity using population-level, whole genome resequencing data obtained from annual Mimulus guttatus individuals collected across a rugged environment landscape. We found substantial variation in how genetic differentiation is structured both within and between chromosomes, although, in contrast to other studies, known inversion polymorphisms appear to serve only minor roles in this heterogeneity. In addition, much of the genome can be clustered into eight among-population genetic differentiation patterns, but only two of these clusters are particularly consistent with patterns of isolation by distance. By performing genotype-environment association analysis, we also identified genomic intervals where local adaptation to specific climate factors has accentuated genetic differentiation among populations, and candidate genes in these windows indicate climate adaptation may proceed through changes affecting specialized metabolism, drought resistance, and development. Finally, by integrating our findings with previous studies, we show that multiple aspects of plant reproductive biology may be common targets of balancing selection and that variants historically involved in climate adaptation among populations have probably also fuelled rapid adaptation to microgeographic environmental variation within sites.

Genome-wide identification and expression analysis of terpene synthase gene family in Aquilaria sinensis

Agarwood is the resinous portion of Aquilaria trees, and has been widely used as medicine and incense. Sesquiterpenes are the main chemical characteristic constituents of agarwood. Terpene synthase (TPS) is a critical enzyme responsible for biosynthesis of sesquiterpene compounds. However, limited information is available on genome-wide identification and characterization of the TPS family in Aquilaria trees. In this study, TPS gene family was identified and characterized in Aquilaria sinensis by bioinformatics methods. The expression of those genes was analyzed by RNA-seq and quantitative real-time PCR. Transcription factors regulating TPS gene expression were identified by yeast one-hybrid and dual-luciferase assay. In total, 26 AsTPS genes (AsTPS1-AsTPS26) were identified, which were classified into five subgroups. Many putative cis-elements putatively involved in stresses and phytohormones (especially jasmonic acid) were identified in the promoter regions of AsTPSs, suggesting that AsTPSs genes may be regulated by stresses and jasmonic acid. Expression analysis revealed seven TPS genes encoding sesquiterpene synthetases were induced by wounding and methyl jasmonic acid (MeJA), which may be related to sesquiterpene biosynthesis. By yeast one-hybrid screening, a ERF transcription factor AsERF1 was identified to interact with the AsTPS1 promoter. Subcellular localization analysis indicated AsERF1 was a nucleus-localized protein. Transient transfection of AsERF1 in leaves of Nicotiana benthamiana significantly enhanced the promoter activation of AsTPS1, suggesting AsERF1 may participate in sesquiterpene biosynthesis by regulating AsTPS1 expression. These data generated in this study provide a foundation for future studies on functional roles and regulation mechanisms of AsTPS in sesquiterpene biosynthesis and agarwood formation.

Composition of the metabolomic bio-coronas isolated from Ocimum sanctum and Rubia tinctorum

Objective

Nanoharvesting from intact plants, organs, and cultured cells is a method in which nanoparticles are co-incubated with the target tissue, which leads to the internalization of nanoparticles. Internalized nanoparticles are coated in situ with specific metabolites that form a dynamic surface layer called a bio-corona. Our previous study showed that metabolites that form the bio-corona around anatase TiO₂ nanoparticles incubated with leaves of the model plant Arabidopsis thaliana are enriched for flavonoids and lipids. The present study focused on the identification of metabolites isolated by nanoharvesting from two medicinal plants, Ocimum sanctum (Tulsi) and Rubia tinctorum (common madder).

Results

To identify metabolites that form the bio-corona, Tulsi leaves and madder roots were incubated with ultra-small anatase TiO₂ nanoparticles, the coated nanoparticles were collected, and the adsorbed molecules were released from the nanoparticle surface and analyzed using an untargeted metabolomics approach. Similar to the results in which Arabidopsis tissue was used as a source of metabolites, TiO₂ nanoparticle bio-coronas from Tulsi and madder were enriched for flavonoids and lipids, suggesting that nanoharvesting has a wide-range application potential. The third group of metabolites enriched in bio-coronas isolated from both plants were small peptides with C-terminal arginine and lysine residues.

A Comprehensive Survey on the Terpene Synthase Gene Family Provides New Insight into Its Evolutionary Patterns

Terpenes are organic compounds and play important roles in plant growth and development as well as in mediating interactions of plants with the environment. Terpene synthases (TPSs) are the key enzymes responsible for the biosynthesis of terpenes. Although some species were employed for the genome-wide identification and characterization of the TPS family, limited information is available regarding the evolution, expansion, and retention mechanisms occurring in this gene family. We performed a genome-wide identification of the TPS family members in 50 sequenced genomes. Additionally, we also characterized the TPS family from aromatic spearmint and basil plants using RNA-Seq data. No TPSs were identified in algae genomes but the remaining plant species encoded various numbers of the family members ranging from 2 to 79 full-length TPSs. Some species showed lineage-specific expansion of certain subfamilies, which might have contributed toward species or ecotype divergence or environmental adaptation. A large-scale family expansion was observed mainly in dicot and monocot plants, which was accompanied by frequent domain loss. Both tandem and segmental duplication significantly contributed toward family expansion and expression divergence and played important roles in the survival of these expanded genes. Our data provide new insight into the TPS family expansion and evolution and suggest that TPSs might have originated from isoprenyl diphosphate synthase genes.

TulsiPIN: An Interologous Protein Interactome of Ocimum tenuiflorum

Ocimum tenuiflorum, commonly known as holy basil or tulsi, is globally recognized for its multitude of medicinal properties. However, a comprehensive study revealing the complex interplay among its constituent proteins at subcellular level is still lacking. To bridge this gap, in this work, a genome-scale interologous protein-protein interaction (PPI) network, TulsiPIN, is developed using 36 template plants, which consists of 13 660 nodes and 327 409 binary interactions. A high confidence network, hc-TulsiPIN, consisting of 7719 nodes having 95 532 interactions is inferred using domain-domain interaction information along with interolog-based statistics, and its reliability is assessed using pathway enrichment, functional homogeneity, and protein colocalization of PPIs. Examination of topological features revealed that hc-TulsiPIN possesses conventional properties, like small-world, scale-free, and modular architecture. A total of 1625 vital proteins are predicted by statistically evaluating hc-TulsiPIN with two ensembles of corresponding random networks, each consisting of 10 000 realizations of Erdoős-Rényi and Barabási-Albert models. Also, numerous regulatory proteins like transcription factors, transcription regulators, and protein kinases are profiled. Using 36 guide genes participating in 9 secondary metabolite biosynthetic pathways, a subnetwork consisting of 171 proteins and 612 interactions was constructed, and 127 of these proteins could be successfully characterized. Detailed information of TulsiPIN is available at https://cuhpcbbtulsipin.shinyapps.io/tulsipin_v0/ .

The role of volatiles in plant communication

Volatiles mediate the interaction of plants with pollinators, herbivores and their natural enemies, other plants and micro-organisms. With increasing knowledge about these interactions the underlying mechanisms turn out to be increasingly complex. The mechanisms of biosynthesis and perception of volatiles are slowly being uncovered. The increasing scientific knowledge can be used to design and apply volatile-based agricultural strategies.