A de novo long-read genome assembly of the sacred datura plant (Datura wrightii) reveals a role of tandem gene duplications in the evolution of herbivore-defense response.

The sacred datura plant (Solanales: Solanaceae: Datura wrightii) has been used to study plant-herbivore interactions for decades. The wealth of information that has resulted leads it to have potential as a model system for studying the ecological and evolutionary genomics of these interactions. We present a de novo Datura wrightii genome assembled using PacBio HiFi long-reads. Our assembly is highly complete and contiguous (N50 = 179Mb, BUSCO Complete = 97.6%). We successfully detected a previously documented ancient whole genome duplication using our assembly and have classified the gene duplication history that generated its coding sequence content. We use it as the basis for a genome-guided differential expression analysis to identify the induced responses of this plant to one of its specialized herbivores (Coleoptera: Chrysomelidae: Lema daturaphila). We find over 3000 differentially expressed genes associated with herbivory and that elevated expression levels of over 200 genes last for several days. We also combined our analyses to determine the role that different gene duplication categories have played in the evolution of Datura-herbivore interactions. We find that tandem duplications have expanded multiple functional groups of herbivore responsive genes with defensive functions, including UGT-glycosyltranserases, oxidoreductase enzymes, and peptidase inhibitors. Overall, our results expand our knowledge of herbivore-induced plant transcriptional responses and the evolutionary history of the underlying herbivore-response genes.

Coevolutionary transitions from antagonism to mutualism explained by the Co-Opted Antagonist Hypothesis.

There is now good evidence that many mutualisms evolved from antagonism; why or how, however, remains unclear. We advance the Co-Opted Antagonist (COA) Hypothesis as a general mechanism explaining evolutionary transitions from antagonism to mutualism. COA involves an eco-coevolutionary process whereby natural selection favors co-option of an antagonist to perform a beneficial function and the interacting species coevolve a suite of phenotypic traits that drive the interaction from antagonism to mutualism. To evaluate the COA hypothesis, we present a generalized eco-coevolutionary framework of evolutionary transitions from antagonism to mutualism and develop a data-based, fully ecologically-parameterized model of a small community in which a lepidopteran insect pollinates some of its larval host plant species. More generally, our theory helps to reconcile several major challenges concerning the mechanisms of mutualism evolution, such as how mutualisms evolve without extremely tight host fidelity (vertical transmission) and how ecological context influences evolutionary outcomes, and vice-versa.

Datura genome reveals duplications of psychoactive alkaloid biosynthetic genes and high mutation rate following tissue culture.

BACKGROUND: Datura stramonium (Jimsonweed) is a medicinally and pharmaceutically important plant in the nightshade family (Solanaceae) known for its production of various toxic, hallucinogenic, and therapeutic tropane alkaloids. Recently, we published a tissue-culture based transformation protocol for D. stramonium that enables more thorough functional genomics studies of this plant. However, the tissue culture process can lead to undesirable phenotypic and genomic consequences independent of the transgene used. Here, we have assembled and annotated a draft genome of D. stramonium with a focus on tropane alkaloid biosynthetic genes. We then use mRNA sequencing and genome resequencing of transformants to characterize changes following tissue culture. RESULTS: Our draft assembly conforms to the expected 2 gigabasepair haploid genome size of this plant and achieved a BUSCO score of 94.7% complete, single-copy genes. The repetitive content of the genome is 61%, with Gypsy-type retrotransposons accounting for half of this. Our gene annotation estimates the number of protein-coding genes at 52,149 and shows evidence of duplications in two key alkaloid biosynthetic genes, tropinone reductase I and hyoscyamine 6 ß-hydroxylase. Following tissue culture, we detected only 186 differentially expressed genes, but were unable to correlate these changes in expression with either polymorphisms from resequencing or positional effects of transposons. CONCLUSIONS: We have assembled, annotated, and characterized the first draft genome for this important model plant species. Using this resource, we show duplications of genes leading to the synthesis of the medicinally important alkaloid, scopolamine. Our results also demonstrate that following tissue culture, mutation rates of transformed plants are quite high (1.16 × 10- 3 mutations per site), but do not have a drastic impact on gene expression.

Molecular cloning and functional analysis of hyoscyamine 6ß-hydroxylase (H6H) in the poisonous and medicinal plant Datura innoxia mill.

Datura innoxia Mill., a traditional Chinese herbal medicine, produces tropane alkaloids such as hyoscyamine and scopolamine. Scopolamine has a larger demand than hyoscyamine due to its stronger pharmacological effects and fewer side reactions. It is extracted from solanaceous plants. However, the content of scopolamine is lower than hyoscyamine in D. innoxia. Hyoscyamine 6ß-hydroxylase (H6H, EC1.14.11.11) is the key enzyme which can catalyze hyoscyamine to form scopolamine. In this study, a cDNA encoding H6H was cloned from D. innoxia roots and named Dih6h. The full-length cDNA is 1413 bp in length with a 1044-bp open reading frame encoding 347 amino acids. The deduced protein sequence of D. innoxia H6H (DiH6H) shared high identity with H6Hs from other plants. The DiH6H was heterologously expressed in Escherichia coli and purified via His-tag affinity technique. The recombinant DiH6H showed activity in transforming hyoscyamine to scopolamine. Despite Dih6h mRNA was detected in various tissues, its levels in roots were higher than that in other tissues. Indeed, scopolamine accumulation was low in roots, but it was very high in aerial parts, especially in flowers and seeds. These observations suggest that scopolamine may be synthesized in the roots and subsequently transported to the aerial parts. To further verify in vivo function of DiH6H, the cDNA of DiH6H was overexpressed in D. innoxia hairy roots. As expected, an increase of scopolamine production was observed in the positive transformants. The results provide a potential strategy for increasing scopolamine yield by metabolic engineering of its biosynthetic pathway in D. innoxia.

Comprehensive Analysis of Phytochemical Constituents and Ethnopharmacological Investigation of Genus Datura.

The genus Datura comprises wild shrub plants that belong to the Solanaceae family. Naturally, they possess both medicinal and poisonous properties due to the presence of many biologically active phytochemical constituents. Traditionally, Datura had been used for mystic and religious purposes, as a natural drug to treat asthma, pain, gout, boils, abscesses, and wounds, and as psychoactive infusions and fumitories. Different Datura species exhibit diverse ethnopharmacological activities against different diseases, and many ancient and traditional cultures have used various forms of Datura to treat ailments and to prevent many diseases. In this article, we comprehensively summarize various phytochemical constituents isolated from Datura, their pharmacological properties against different diseases, parts of the plants used as traditional therapeutic agents, regions where they are located, and botanical descriptions of different Datura species. The ethnopharmacological properties of Datura may provide new insights for discovery and development of natural drugs. Further research is needed for the investigation of mechanisms of action and to develop safety profiles of the phytochemical constituents isolated from Datura species.

The genus Datura L. (Solanaceae) in Mexico and Spain - Ethnobotanical perspective at the interface of medical and illicit uses.

ETHNOPHARMACOLOGICAL RELEVANCE: The different species of the genus Datura have been used traditionally by some pre-Columbian civilizations, as well as in medieval rituals linked to magic and witchcraft in both Mexico and Europe. It is also noteworthy the use of different alkaloids obtained from the plants for medicinal purposes in the treatment of various groups of diseases, especially of the respiratory and muscularskeletal systems. AIM OF THE STUDY: A review of the ethnobotanical uses of the genus Datura in Mexico and Spain has been conducted. We focus on the medicinal and ritualistic uses included in modern ethnobotanical studies, emphasizing the historical knowledge from post-colonial American Codices and medieval European texts. Datura's current social emergency as a drug of recreation and leisure, as well as its link to crimes of sexual abuse is also considered. The work is completed with some notes about the distribution and ecology of the different species and a phytochemical and pharmacological review of Datura alkaloids, necessary to understand their arrival in Europe and the ethnobotanical uses made since then MATERIALS AND METHODS: A literature review and compilation of information on traditional medicinal uses of the genus has been carried out from the main electronic databases. Traditional volumes (codices) have also been consulted in libraries of different institutions. Consultations have been made with the National Toxicological Services of Spain and Mexico for toxicological data. RESULTS: A total of 118 traditional uses were collected in both territories, 111 medicinal ones to be applied in 76 conditions or symptoms included in 13 pathological groups. Although there are particular medicinal uses in the two countries, we found up to 15 similar uses, of which 80% were previously mentioned in post-Colonial American codices. Applications in the treatment of asthma and rheumatism are also highlighted. Apart from medicinal uses, it is worth noting their cultural and social uses, in the case of Mexico relating to diseases such as being scared, astonishment or falling in love, and in the case of Spain, as a recreational drug and lately, for criminal purposes. CONCLUSIONS: This review highlights the variety of uses traditionally given to the different species in both territories. The fact that most of the coincident or similar uses in both countries also appear in the classical codices can be found an example of the flow, not only of the plants from America to Europe, but also of their associated information. It is also relevant that particular uses have derived in both countries, reflecting the difference in the cultural factors and traditions linked to rituals and cultural practices. Finally, the significant growth of Datura consumption in recent years as a drug of leisure and recreation, as well as in crimes of sexual submission, should be considered as research of maximum relevance in the field of forensic botany and toxicology.

Identification of Datura Species Involved in a Food-Poisoning Case Using LC-MS/MS and DNA Barcording.

A food-poisoning case due to eating the roots of Datura occurred in Kawasaki City, Japan in 2014. The Datura plant was mistakenly collected instead of burdock in a domestic garden. The roots of these plants are quite similar to each other. We presumed that the specimen was the root of Datura, but it was difficult to classify it only from the morphology. Using LC-MS/MS, we detected atropine and scopolamine from the remaining plant specimen. Therefore, we applied the DNA barcoding method. The results showed that the specimen was classified into Solanaceae family, but not Asteraceae family. Thus, the specimen was confirmed to be Datura species based on both chemical and genetic analyses.

Establishment, Culture, and Scale-up of Brugmansia candida Hairy Roots for the Production of Tropane Alkaloids.

Brugmansia candida (syn. Datura candida) is a South American native plant that produces tropane alkaloids. Hyoscyamine, 6ß-hydroxyhyoscyamine (anisodamine), and scopolamine are the most important ones due to their anticholinergic activity. These bioactive compounds have been historically and widely applied in medicine and their demand is continuous. Their chemical synthesis is costly and complex, and thereby, these alkaloids are industrially produced from natural producer plants. The production of these secondary metabolites by plant in vitro cultures such as hairy roots presents certain advantages over the natural source and chemical synthesis. It is well known that hairy roots produced by Agrobacterium rhizogenes infection are fast-growing cultures, genetically stable and able to grow in hormone-free media. Additionally, recent progress achieved in the scaling up of hairy root cultures makes this technology an attractive tool for industrial processes. This chapter is focused on the methods for the induction and establishment of B. candida hairy roots. In addition, the scaling up of hairy root cultures in bioreactors and tropane alkaloid analysis is discussed.

Unravelling the architecture and dynamics of tropane alkaloid biosynthesis pathways using metabolite correlation networks.

The tropane alkaloid spectrum in Solanaceae is highly variable within and between species. Little is known about the topology and the coordination of the biosynthetic pathways leading to the variety of tropine and pseudotropine derived esters in the alkaloid spectrum, or about the metabolic dynamics induced by tropane alkaloid biosynthesis stimulating conditions. A good understanding of the metabolism, including all ramifications, is however necessary for the development of strategies to increase the abundance of pharmacologically interesting compounds such as hyoscyamine and scopolamine. The present study explores the tropane alkaloid metabolic pathways in an untargeted approach involving a correlation-based network analysis. Using GC-MS metabolite profiling, the variation and co-variation among tropane alkaloids and primary metabolites was monitored in 60 Datura innoxia Mill. individuals, of which half were exposed to tropane alkaloid biosynthesis stimulating conditions by co-culture with Agrobacterium rhizogenes. Considerable variation was evident in the relative proportions of the tropane alkaloids. Remodeling of the tropane alkaloid spectrum under co-culture with A. rhizogenes involved a specific and strong increase of hyoscyamine production and revealed that the accumulation of hyoscyamine, 3-tigloyloxy-6,7-epoxytropane, and 3-methylbutyryloxytropane was controlled independently of the majority of tropane alkaloids. Based on correlations between metabolites, we propose a biosynthetic origin of hygrine, the order of esterification of certain di-oxygenated tropanes, and that the rate of acetoxylation contributes to control of hyoscyamine production. Overall, this study shows that the biosynthesis of tropane alkaloids may be far more complex and finely controlled than previously expected.

Phylogenetic correlations among chemical and physical plant defenses change with ontogeny.

Theory predicts patterns of defense across taxa based on notions of tradeoffs and synergism among defensive traits when plants and herbivores coevolve. Because the expression of characters changes ontogenetically, the evolution of plant strategies may be best understood by considering multiple traits along a trajectory of plant development. Here we addressed the ontogenetic expression of chemical and physical defenses in 12 Datura species, and tested for macroevolutionary correlations between defensive traits using phylogenetic analyses. We used liquid chromatography coupled to mass spectrometry to identify the toxic tropane alkaloids of Datura, and also estimated leaf trichome density. We report three major patterns. First, we found different ontogenetic trajectories of alkaloids and leaf trichomes, with alkaloids increasing in concentration at the reproductive stage, whereas trichomes were much more variable across species. Second, the dominant alkaloids and leaf trichomes showed correlated evolution, with positive and negative associations. Third, the correlations between defensive traits changed across ontogeny, with significant relationships only occurring during the juvenile phase. The patterns in expression of defensive traits in the genus Datura are suggestive of adaptation to complex selective environments varying in space and time.

[DNA Molecular Identification of Datura Medicinal Plants Using ITS2 Barcode Sequence].

OBJECTIVE: To identify Datura medicinal plants in Solanaceae using DNA barcode technique and ITS2 sequence. METHODS: The second internal transcribed spacer (ITS2) of Datura and Nicotiana medicinal plant samples was amplified by PCR and sequenced. To expand scope of the research topic, ITS2 sequences of related species were downloaded from GenBank. Sequence assembly and consensus sequence generation were performed by CodonCode Aligner. All the ITS2 sequences in the study were compared and analyzed using software DNAMAN. The related data analysis and processing were performed using software MEGA 5. 10 and the NJ tree was constructed. The ITS2 secondary structure was predicted using ITS2 web server, and distinguishing differences of the ITS2 secondary structures of the samples. RESULTS: In the cluster dendrogram, all of samples were clustered into three branches. The plants of Nicotiana were clustered into a single branch, and the same as Datura (Brugmansia) arborea, which is similar to the results of previous studies. These proved that Brugmansia and Datura belonged to two different genera. Other species of Datura were clustered into a branch where all the intra-species samples were clustered to one branch respectively and obviously distinguished, which showed monophyletic. Bootstrap support rates between each two branches were more than 95%. CONCLUSION: ITS2 sequences have great potential in terms of systematics study and variety identification.

[Cloning and expression of the key enzyme hyoscyamine 6 beta-hydroxylase gene (DaH6H) in scopolamine biosynthesis of Datura arborea].

Hyoscyamine 6 beta-hydroxylase (H6H) is the last rate-limiting enzyme directly catalyzing the formation of scopolamine in tropane alkaloids (TAs) biosynthesis pathway. It is the primary target gene in the genetic modification of TAs metabolic pathway. Full-length cDNA and gDNA sequences of a novel H6H gene were cloned from Datura arborea (DaH6H, GenBank accession numbers for cDNA and gDNA are KR006981 and KR006983, respectively). Nucleotide sequence analysis reveals an open reading frame of 1375 bp encoding 347 amino acids in the cDNA of DaH6H, while the gDNA of DaH6H contains four exons and three introns, with the highest similarity to the gDNA of H6H from D. stramonium. DaH6H also exhibited the most identity of 90.5% with DsH6H in amino acids and harbored conserved 2-oxoglutarate binding motif and two iron binding motifs. The expression level of DaH6H was highest in the mature leaf, followed by the secondary root, and with no expression in the primary root based on qPCR analysis. Its expression was inhibited by MeJA. DaH6H was expressed in E. coli and a 39 kD recombinant protein was detected in SDS-PAGE. Comparison of the contents of scopolamine and hyoscyamine in various TAs-producing plants revealed that D. arborea was one of the rare scopolamine predominant plants. Cloning of DaH6H gene will allow more research in the molecular regulatory mechanism of TAs biosynthesis in distinct plants and provide a new candidate gene for scopolamine metabolic engineering.

Aneuploidy in plants and flies: the origin of studies of genomic imbalance.

The early principles of the impact of aneuploidy were determined in plants and Drosophila. Here we summarize the classical results and then relate them to more current studies of gene expression in these taxa. As a general rule, aneuploidy is detrimental, even to the point of lethality, compared to changes in the dosage of the whole genome. Gene expression studies demonstrate an analogous relationship, namely that changes in dosage of chromosomes or chromosomal segments will modulate many genes but changes in whole ploidy have much less of an effect. One of the most common trans-acting effects is an inverse response of a gene to the altered dosage of a chromosomal segment. This effect can produce dosage compensation when it occurs for a gene that is also present in the varied region. Some open questions in the field of aneuploidy research are discussed.

Herbivores can select for mixed defensive strategies in plants.

Resistance and tolerance are the most important defense mechanisms against herbivores. Initial theoretical studies considered both mechanisms functionally redundant, but more recent empirical studies suggest that these mechanisms may complement each other, favoring the presence of mixed defense patterns. However, the expectation of redundancy between tolerance and resistance remains unsupported. In this study, we tested this assumption following an ecological genetics field experiment in which the presence/absence of two herbivores (Lema daturaphila and Epitrix parvula) of Datura stramonium were manipulated. In each of three treatments, genotypic selection analyses were performed and selection patterns compared. Our results indicated that selection on resistance and tolerance was significantly different between the two folivores. Tolerance and resistance are not redundant defense strategies in D. stramonium but instead functioned as complementary defenses against both beetle species, favoring the evolution of a mixed defense strategy. Although each herbivore was selected for different defense strategies, the observed average tolerance and resistance were closer to the adaptive peak predicted against E. parvula and both beetles together. In our experimental population, natural selection imposed by herbivores can favor the evolution of mixed defense strategies in plants, accounting for the presence of intermediate levels of tolerance and resistance.

[Identification of Daturae flos and its adulterants based on DNA barcoding technique].

To identify the original plant of Daturae Flos from its adulterants by DNA barcoding, the sequences of ITS2, psbA-trnH, matK, rbcL of four species including Datura metel, Darura innoxia, Darura stramonium and Brugmansia arborea were compared and analyzed. The PCR and sequencing success rate of the four regions (ITS2, psbA-trnH, matK, rbcL) was 100%, 90%, 100% and 85%, respectively. Sequences were assembled with CodonCode Aligner. K2P distances were calculated and NJ tree was performed by MEGA 4.1. Thirty SNPs were found among ITS2 sequences, and 33 insert/deletes were found among psbA-trnH intergenic regions. The interspecific K2P distance of ITS2 and psbA-trnH was obviously higher than that of the intraspecific one. As to matK and rbcL, there was no "Barcoding Gap" existing between inter- and intra-specific distances. The NJ trees of the four regions/combinations were built separately. Samples of Brugmansia arborea were clustered into one clade, and the other species of Datura L. formed another clade. The results showed that either ITS2 or psbA-trnH was useful to identify Daturae Flos from its adulterants.

Transcriptional regulation of the rice arginine decarboxylase (Adc1) and S-adenosylmethionine decarboxylase (Samdc) genes by methyl jasmonate.

We investigated the effect of methyl jasmonate (MeJa) treatment on the expression of two genes in the rice polyamine biosynthesis pathway and on the polyamine content in wild type plants and transgenic rice plants expressing a Datura stramonium (Ds) Adc cDNA, the latter accumulating up to three-fold the normal level of putrescine. Exogenous MeJa transiently inhibited the expression of OsAdc1, OsSamdc and Spermidine synthase (OsSpds) genes in the polyamine biosynthesis pathway, probably through transcriptional repression. There was also a similar negative impact on the DsAdc transgene in transgenic plants, even though a constitutive promoter was used to drive transgene expression. The free putrescine content was reduced significantly in the leaves of both wild type and transgenic plants in response to MeJa, although the magnitude of the effect was greater in wild type plants. We discuss our findings with respect to the previously proposed threshold model of polyamine metabolism in plants subjected to abiotic stress.

Variation in herbivore and methyl jasmonate-induced volatiles among genetic lines of Datura wrightii.

Many plant species produce volatile organic compounds after being damaged by herbivores. The production of volatiles also may be induced by exposing plants to the plant hormone, jasmonic acid, or its volatile ester, methyl jasmonate. This study addresses the induction of the production volatile organic compounds among genetic lines of Datura wrightii. Within populations, some plants produce glandular trichomes, whereas others produce nonglandular trichomes, and trichome phenotype is controlled by a single dominant gene. Glandular trichomes not only confer resistance to some herbivorous insects, but they also inhibit many natural enemies of those herbivores. Because of the potential benefit of natural enemies that use volatile cues to find individuals of the non-glandular phenotype, it is reasonable to ask if plants of D. wrightii that differ in trichome morphology might produce different blends of volatile compounds. Volatile compounds were collected from eight genetic lines of plants that had been backcrossed for three generations. Volatiles were collected from pairs of sibling plants before and after insect damage or treatment with methyl jasmonate. Within each pair, one sib expressed glandular trichomes and the other expressed nonglandular trichomes. Overall, plants produced an array of at least 17 compounds, most of which were sesquiterpenes. Total production of volatiles increased from 3.9- to 16.2-fold among genetic lines after insect damage and from 3.6- to 32-fold in plants treated with methyl jasmonate. The most abundant compound was (E)-beta-caryophyllene. This single compound comprised from 17 to 59% of the volatiles from insect-damaged plants and from 24 to 88% of the volatiles from plants treated with methyl jasmonate, depending upon genetic line. The production of (E)-beta-caryophyllene by the original male parents of the eight genetic lines was significantly related to the mean production of their third-generation backcross progeny indicating that the variation in the production of (E)-beta-caryophyllene was inherited. Blends did not differ qualitatively or quantitatively between sibs expressing glandular or nonglandular trichomes.

Positive selection for single amino acid change promotes substrate discrimination of a plant volatile-producing enzyme.

We used a combined evolutionary and experimental approach to better understand enzyme functional divergence within the SABATH gene family of methyltransferases (MTs). These enzymes catalyze the formation of a variety of secondary metabolites in plants, many of which are volatiles that contribute to floral scent and plant defense such as methyl salicylate and methyl jasmonate. A phylogenetic analysis of functionally characterized members of this family showed that salicylic acid methyltransferase (SAMT) forms a monophyletic lineage of sequences found in several flowering plants. Most members of this lineage preferentially methylate salicylic acid (SA) as compared with the structurally similar substrate benzoic acid (BA). To investigate if positive selection promoted functional divergence of this lineage of enzymes, we performed a branch-sites test. This test showed statistically significant support (P<0.05) for positive selection in this lineage of MTs (dN/dS=10.8). A high posterior probability (pp=0.99) identified an active site methionine as the only site under positive selection in this lineage. To investigate the potential catalytic effect of this positively selected codon, site-directed mutagenesis was used to replace Met with the alternative amino acid (His) in a Datura wrightii floral-expressed SAMT sequence. Heterologous expression of wild-type and mutant D. wrightii SAMT in Escherichia coli showed that both enzymes could convert SA to methyl salicylate and BA to methyl benzoate. However, competitive feeding with equimolar amounts of SA and BA showed that the presence of Met in the active site of wild-type SAMT resulted in a >10-fold higher amount of methyl salicylate produced relative to methyl benzoate. The Met156His-mutant exhibited little differential preference for the 2 substrates because nearly equal amounts of methyl salicylate and methyl benzoate were produced. Evolution of the ability to discriminate between the 2 substrates by SAMT may be advantageous for efficient production of methyl salicylate, which is important for pollinator attraction as well as pathogen and herbivore defense. Because BA is a likely precursor for the biosynthesis of SA, SAMT might increase methyl salicylate levels directly by preferential methylation and indirectly by leaving more BA to be converted into SA.

Historical evidence for a pre-Columbian presence of Datura in the Old World and implications for a first millennium transfer from the New World.

Datura (Solanaceae)is a small genus of plants that,for long, was thought to occur naturally in both the New and Old Worlds. However, recent studies indicate that all species in the genus originated in the Americas. This finding has prompted the conclusion that no species of Datura could have been present in the Old World prior to its introduction there by Europeans in the early 16th century CE. Further, the textual evidence traditionally cited in support of a pre-Columbian Old World presence of Datura species is suggested to be due to the misreading of classical Greek and Arabic sources. As a result, botanists generally accept the opinion that Datura species were transferred into the Old World in the post-Columbian period. While the taxonomic and geographic evidence for a New World origin for all the Datura species appears to be well supported, the assertion that Datura species were not known in the Old World prior to the 16th century is based on a limited examination of the pre-Columbian non-Anglo sources. We draw on old Arabic and Indic texts and southern Indian iconographic representations to show that there is conclusive evidence for the pre-Columbian presence of at least one species of Datura in the Old World. Given the systematic evidence for a New World origin of the genus, the most plausible explanation for this presence is a relatively recent but pre-Columbian (probably first millennium CE) transfer of at least one Datura species, D. metel, into the Old World. Because D. metel is a domesticated species with a disjunct distribution,this might represent an instance of human-mediated transport from the New World to the Old World, as in the case of the sweet potato (Ipomoea batatas).

Comparison of the nucleotide sequences of ferredoxin-cDNAs among some Datura plants.

The nucleotide sequences of partial ferredoxin (Fd)-cDNAs (corresponding to the amino acid sequence of 22-87 in the total 97 amino acids of ferredoxin) were determined for Datura arborea, D. stramonium, D. metel, and related Datura plants. Non-synonymous substitutions were noted at 4 positions and a synonymous substitution was seen at position 82 (Gln [CAA] (arborea) vs. Gln [CAG] (stramonium and metel)). The nucleotide sequence of Fd-cDNA may provide more detailed information regarding the relative taxonomic positions of plants than the amino acid sequence. However, Datura plants in the same section (metel, fastuosa, and innoxia) and of different varieties (stramonium var. stramonium and stramonium var. tatula) showed identical Fd-cDNA nucleotide sequences. This result suggests that there are very close relationships among the plants in each group.