Capsiate-Rich Fraction of Capsicum annuum Induces Muscular Glucose Uptake, Ameliorates Rosiglitazone-Induced Adipogenesis, and Exhibits Activation of NRs Regulating Multiple Signaling Pathways.

Capsiate is a key ingredient in the fruits of a nonpungent cultivar of Capsicum annuum. We investigated the effects of a C. annuum extract (CE) and a capsiate-rich fraction of CE (CR) on nuclear receptors involved in multiple signaling pathways, glucose uptake, and adipogenesis in comparison to pure capsiate (Ca). Similar to the effect of Ca (100 µM), CE (500 µg/mL) and CR (100 µg/mL) caused the activation of PPARα and PPARγ (>3-fold), while CR also activated LXR and NRF2 (>2 fold). CR (200 µg/mL) and Ca (100 µM) decreased lipid accumulation (22.6 ± 14.1 and 49.7 ± 7.3%, respectively) in adipocytes and increased glucose uptake (44.7 ± 6.2 and 30.1 ± 12.2%, respectively) in muscle cells and inhibited the adipogenic effect induced by rosiglitazone by 41.2 ± 5.6 and 13.9 ± 4.3%, respectively. This is the first report to reveal the agonistic action of CR and Ca on multiple nuclear receptors along with their enhanced glucose uptake and antiadipogenic effects. The results indicate the potential utility of the capsiate-rich fraction of C. annuum in alleviating the symptoms of metabolic syndrome and in preventing the undesired adipogenic effects of full PPARγ agonists such as rosiglitazone.

Discovery and characterization of sweetpotato's closest tetraploid relative.

The origin of sweetpotato, a hexaploid species, is poorly understood, partly because the identity of its tetraploid progenitor remains unknown. In this study, we identify, describe and characterize a new species of Ipomoea that is sweetpotato's closest tetraploid relative known to date and probably a direct descendant of its tetraploid progenitor. We integrate morphological, phylogenetic, and genomic analyses of herbarium and germplasm accessions of the hexaploid sweetpotato, its closest known diploid relative Ipomoea trifida, and various tetraploid plants closely related to them from across the American continent. We identify wild autotetraploid plants from Ecuador that are morphologically distinct from Ipomoea batatas and I. trifida, but monophyletic and sister to I. batatas in phylogenetic analysis of nuclear data. We describe this new species as Ipomoea aequatoriensis T. Wells & P. Muñoz sp. nov., distinguish it from hybrid tetraploid material collected in Mexico; and show that it likely played a direct role in the origin of sweetpotato's hexaploid genome. This discovery transforms our understanding of sweetpotato's origin.

Genetic Identity, Diversity, and Population Structure of CIP's Sweetpotato (I. batatas) Germplasm Collection.

The in trust sweetpotato collection housed by the International Center of Potato (CIP) is one of the largest assemblages of plant material representing the genetic resources of this important staple crop. The collection currently contains almost 6,000 accessions of Ipomoea batatas (cultivated sweetpotato) and over 1,000 accessions of sweetpotato crop wild relatives (CWRs). In this study, the entire cultivated collection (5,979 accessions) was genotyped with a panel of 20 simple sequence repeat (SSR) markers to assess genetic identity, diversity, and population structure. Genotyping and phenotyping of in vitro plantlets and mother plants were conducted simultaneously on 2,711 accessions (45% of the total collection) to identify and correct possible genetic identity errors which could have occurred at any time over the thirty plus years of maintenance in the in vitro collection. Within this group, 533 accessions (19.6%) had errors in identity. Field evaluations of morphological descriptors were carried out to confirm the marker data. A phylogenetic tree was constructed to reveal the intraspecific relationships in the population which uncovered high levels of redundancy in material from Peru and Latin America. These genotypic data were supported by morphological data. Population structure analysis demonstrated support for four ancestral populations with many of the accessions having lower levels of gene flow from the other populations. This was especially true of germplasm derived from Peru, Ecuador, and Africa. The set of 20 SSR markers was subsequently utilized to examine a subset of 189 accessions from the USDA sweetpotato germplasm collection and to identify and reconcile potential errors in the identification of clones shared between these collections. Marker analysis demonstrated that the USDA subset of material had 65 unique accessions that were not found in the larger CIP collection. As far as the authors are aware, this is the first report of genotyping an entire sweetpotato germplasm collection in its entirety.

Citrullus ecirrhosus: Wild Source of Resistance Against Bemisia tabaci (Hemiptera: Aleyrodidae) for Cultivated Watermelon.

Members of the highly polyphagous Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) species complex cause major crop damage by feeding and by transmitting plant viruses. The Middle East-Asia Minor 1 (MEAM1) of the B. tabaci complex is by far the most problematic whitefly affecting crops including cultivated watermelon (Citrullus lanatus; Cucurbitaceae: Cucurbitales). Watermelon cultivars share a narrow genetic base and are highly susceptible to whiteflies. We studied the potential of C. ecirrhosus, a perennial desert species that can be hybridized with C. lanatus, as a source of whitefly resistance for cultivated watermelon. The results of this study indicate that C. ecirrhosus offers resistance (although not total) against the MEAM1 B. tabaci based on, at least, antibiosis and antixenosis. Whitefly performance concerning developmental survival, body size attainment, and nonpreference were suppressed on C. ecirrhosus compared with the watermelon cultivar 'Sugar Baby'. Also, our olfactometer results indicated that the adults were less attracted to leaf volatiles of C. ecirrhosus. Although there is a pungent odor associated with the leaves of C. ecirrhosus, the leaf volatiles had no toxic effect on adult whitefly survival as compared with cultivated watermelon. We also demonstrated that plants of C. ecirrhosus can be clonally propagated from vine cuttings of the parent plant. Using traditional breeding procedures, C. ecirrhosus was hybridized with C. lanatus and viable F1 and F2 seeds were produced. This is the first report of pest resistance in C. ecirrhosus. This wild species offers a source of resistance against whiteflies for the improvement of cultivated watermelon.

Genetic Diversity and Population Structure of the USDA Sweetpotato (Ipomoea batatas) Germplasm Collections Using GBSpoly.

Sweetpotato (Ipomoea batatas) plays a critical role in food security and is the most important root crop worldwide following potatoes and cassava. In the United States (US), it is valued at over $700 million USD. There are two sweetpotato germplasm collections (Plant Genetic Resources Conservation Unit and US Vegetable Laboratory) maintained by the USDA, ARS for sweetpotato crop improvement. To date, no genome-wide assessment of genetic diversity within these collections has been reported in the published literature. In our study, population structure and genetic diversity of 417 USDA sweetpotato accessions originating from 8 broad geographical regions (Africa, Australia, Caribbean, Central America, Far East, North America, Pacific Islands, and South America) were determined using single nucleotide polymorphisms (SNPs) identified with a genotyping-by-sequencing (GBS) protocol, GBSpoly, optimized for highly heterozygous and polyploid species. Population structure using Bayesian clustering analyses (STRUCTURE) with 32,784 segregating SNPs grouped the accessions into four genetic groups and indicated a high degree of mixed ancestry. A neighbor-joining cladogram and principal components analysis based on a pairwise genetic distance matrix of the accessions supported the population structure analysis. Pairwise FST values between broad geographical regions based on the origin of accessions ranged from 0.017 (Far East - Pacific Islands) to 0.110 (Australia - South America) and supported the clustering of accessions based on genetic distance. The markers developed for use with this collection of accessions provide an important genomic resource for the sweetpotato community, and contribute to our understanding of the genetic diversity present within the US sweetpotato collection and the species.

Parallel evolution of storage roots in morning glories (Convolvulaceae).

BACKGROUND: Storage roots are an ecologically and agriculturally important plant trait that have evolved numerous times in angiosperms. Storage roots primarily function to store carbohydrates underground as reserves for perennial species. In morning glories, storage roots are well characterized in the crop species sweetpotato, where starch accumulates in storage roots. This starch-storage tissue proliferates, and roots thicken to accommodate the additional tissue. In morning glories, storage roots have evolved numerous times. The primary goal of this study is to understand whether this was through parallel evolution, where species use a common genetic mechanism to achieve storage root formation, or through convergent evolution, where storage roots in distantly related species are formed using a different set of genes. Pairs of species where one forms storage roots and the other does not were sampled from two tribes in the morning glory family, the Ipomoeeae and Merremieae. Root anatomy in storage roots and fine roots was examined. Furthermore, we sequenced total mRNA from storage roots and fine roots in these species and analyzed differential gene expression. RESULTS: Anatomical results reveal that storage roots of species in the Ipomoeeae tribe, such as sweetpotato, accumulate starch similar to species in the Merremieae tribe but differ in vascular tissue organization. In both storage root forming species, more genes were found to be upregulated in storage roots compared to fine roots. Further, we find that fifty-seven orthologous genes were differentially expressed between storage roots and fine roots in both storage root forming species. These genes are primarily involved in starch biosynthesis, regulation of starch biosynthesis, and transcription factor activity. CONCLUSIONS: Taken together, these results demonstrate that storage roots of species from both morning glory tribes are anatomically different but utilize a common core set of genes in storage root formation. This is consistent with a pattern of parallel evolution, thus highlighting the importance of examining anatomy together with gene expression to understand the evolutionary origins of ecologically and economically important plant traits.

Distributions, ex situ conservation priorities, and genetic resource potential of crop wild relatives of sweetpotato [Ipomoea batatas (L.) Lam., I. series Batatas].

Crop wild relatives of sweetpotato [Ipomoea batatas (L.) Lam., I. series Batatas] have the potential to contribute to breeding objectives for this important root crop. Uncertainty in regard to species boundaries and their phylogenetic relationships, the limited availability of germplasm with which to perform crosses, and the difficulty of introgression of genes from wild species has constrained their utilization. Here, we compile geographic occurrence data on relevant sweetpotato wild relatives and produce potential distribution models for the species. We then assess the comprehensiveness of ex situ germplasm collections, contextualize these results with research and breeding priorities, and use ecogeographic information to identify species with the potential to contribute desirable agronomic traits. The fourteen species that are considered the closest wild relatives of sweetpotato generally occur from the central United States to Argentina, with richness concentrated in Mesoamerica and in the extreme Southeastern United States. Currently designated species differ among themselves and in comparison to the crop in their adaptations to temperature, precipitation, and edaphic characteristics and most species also show considerable intraspecific variation. With 79% of species identified as high priority for further collecting, we find that these crop genetic resources are highly under-represented in ex situ conservation systems and thus their availability to breeders and researchers is inadequate. We prioritize taxa and specific geographic locations for further collecting in order to improve the completeness of germplasm collections. In concert with enhanced conservation of sweetpotato wild relatives, further taxonomic research, characterization and evaluation of germplasm, and improving the techniques to overcome barriers to introgression with wild species are needed in order to mobilize these genetic resources for crop breeding.

Phylogenetics and diversification of morning glories (tribe Ipomoeeae, Convolvulaceae) based on whole plastome sequences.

PREMISE OF THE STUDY: Morning glories are an emerging model system, and resolving phylogenetic relationships is critical for understanding their evolution. Phylogenetic studies demonstrated that the largest morning glory genus, Ipomoea, is not monophyletic, and nine other genera are derived from within Ipomoea. Therefore, systematic research is focused on the monophyletic tribe Ipomoeeae (ca. 650-900 species). We used whole plastomes to infer relationships across Ipomoeeae. METHODS: Whole plastomes were sequenced for 29 morning glory species, representing major lineages. Phylogenies were estimated using alignments of 82 plastid genes and whole plastomes. Divergence times were estimated using three fossil calibration points. Finally, evolution of root architecture, flower color, and ergot alkaloid presence was examined. KEY RESULTS: Phylogenies estimated from both data sets had nearly identical topologies. Phylogenetic results are generally consistent with prior phylogenetic hypotheses. Higher-level relationships with weak support in previous studies were recovered here with strong support. Molecular dating analysis suggests a late Eocene divergence time for the Ipomoeeae. The two clades within the tribe, Argyreiinae and Astripomoeinae, diversified at similar times. Reconstructed most recent common ancestor of the Ipomoeeae had blue flowers, an association with ergot-producing fungi, and either tuberous or fibrous roots. CONCLUSIONS: Phylogenetic results provide confidence in relationships among Ipomoeeae lineages. Divergence time estimation results provide a temporal context for diversification of morning glories. Ancestral character reconstructions support previous findings that morning glory morphology is evolutionarily labile. Taken together, our study provides strong resolution of the morning glory phylogeny, which is broadly applicable to the evolution and ecology of these fascinating species.

Oil and fatty acid contents in seed of Citrullus lanatus Schrad.

Intact seed of 475 genebank accessions of Citrullus ( C. lanatus var. lanatus and C. lanatus var. citroides) were analyzed for percent oil content using TD-NMR. Extracts from whole seed of 96 accessions of C. lanatus (30 var. citroides, 33 var. lanatus, and 33 egusi), C. colocynthis (n = 3), C. ecirrhosus (n = 1), C. rehmii (n = 1), and Benincasa fistulosa (n = 3) were also analyzed for their fatty acids content. Among the materials analyzed, seed oil content varied from 14.8 to 43.5%. Mean seed oil content in egusi types of C. lanatus was significantly higher (mean = 35.6%) than that of either var. lanatus (mean = 23.2%) or var. citroides (mean = 22.6%). Egusi types of C. lanatus had a significantly lower hull/kernel ratio when compared to other C. lanatus var. lanatus or C. lanatus var. citroides. The principal fatty acid in all C. lanatus materials examined was linoleic acid (43.6-73%). High levels of linoleic acid were also present in the materials of C. colocynthis (71%), C. ecirrhosus (62.7%), C. rehmii (75.8%), and B. fistulosa (73.2%), which were included for comparative purposes. Most all samples contained traces (<0.5%) of arachidonic acid. The data presented provide novel information on the range in oil content and variability in the concentrations of individual fatty acids present in a diverse array of C. lanatus, and its related species, germplasm.

Seed oil and fatty acid content in okra (Abelmoschus esculentus) and related species.

Approximately 1100 genebank accessions of okra (Abelmoschus esculentus) and 540 additional accessions that included six of its related species-A. caillei, A. crinitis, A. esculentus, A. ficulneus, A. manihot, A. moschatus and A. tuberculatus-were evaluated for seed oil content using time domain NMR (TD-NMR). Oil content in seed of A. caillei, A. esculentus, A. ficulneus, A. manihot, A. moschatus and A. tuberculatus was in the ranges 2.51-13.61%, 12.36-21.56%, 6.62-16.7%, 16.1-22.0%, 10.3-19.8% and 10.8-23.2%, respectively. Accession PI639680 (A. tuberculatus) had the highest seed oil content (∼23%). Accessions of A. esculentus with high seed oil content included PI nos. PI274350 (21.5%), PI538082 (20.9%) and PI538097 (20.9%). Values for the three accessions of A. manihot with the highest seed oil content were PI nos. PI639673 (20.4%), PI639674 (20.9%) and PI639675 (21.9%), all representing var. tetraphyllus. Average percent seed oil in materials of A. esculentus from Turkey and Sudan (17.35% and 17.36%, respectively) exceeded the averages of materials from other locations. Ninety-eight accessions (total of six species) were also examined for fatty acid composition. Values of linoleic acid ranged from 23.6-50.65% in A. esculentus. However, mean linoleic acid concentrations were highest in A. tuberculatus and A. ficulneus. Concentrations of palmitic acid were significantly higher in A. esculentus (range of 10.3-36.35%) when compared to that of other species, and reached a maximum in PI489800 Concentrations of palmitic acid were also high in A. caillei (mean = ∼30%). Levels of oleic acid were highest in A. manihot, A. manihot var. tetraphyllus and A. moschatus.

Screening Capsicum chinense fruits for heavy metals bioaccumulation.

Elevated concentrations of heavy metals in edible plants could expose consumers to excessive levels of potentially hazardous chemicals. Sixty-three accessions (genotypes) of Capsicum chinense Jacq, collected from 8 countries of origin were grown in a silty-loam soil under field conditions. At maturity, fruits were collected and analyzed for seven heavy metals (Cd, Cr, Ni, Pb, Zn, Cu, and Mo) concentrations. The main objectives of this investigation were: 1) to determine the concentrations of seven heavy metals in the soil and monitor their accumulation in mature fruits, 2) to categorize the pepper accessions as low or high heavy metal accumulators, and 3) to determine if heavy metal content of the pepper fruit was lower than the permitted limits. Concentrations and relative proportions of heavy metals in pepper fruits of C. chinense varied among accessions. Fruits of Plant Introduction (PI) 355820 accumulated significant concentrations of Cd (0.47 µg g(-1) dry fruit). PI-260522 accumulated the highest concentration of Pb (2.12 µg g(-1) dry fruit) among the 63 accessions tested. This accession (PI-260522) contained about twice the Pb limit on a fresh weight basis. Among the 63 accessions analyzed, PI-238051 contained the highest levels of Ni (17.2 µg g(-1)). We concluded that high accumulator genotypes may be useful for phytoremediation, while, low accumulator accessions might be appropriate selections for growing on Cd-, Pb-, or Ni-contaminated soils to prevent potential human exposure to heavy metals and health hazards through the food chain.

Variability for free sugars and organic acids in Capsicum chinense.

Variability in the concentrations of the chemical constituents that contribute to fruit flavor in Capsicum chinense is poorly documented in the scientific literature. We surveyed fruit of 216 landraces and cultivated varieties of Capsicum chinense acquired from North, Central, and South America, and analyzed these for concentrations of the simple sugars sucrose, glucose, and fructose, and citric, malic, succinic, fumaric, and ascorbic acids. Concentrations (mg/100 g Fresh Weight (FW) of whole fruit) of sucrose, glucose, and fructose in fruit of this species ranged from 0.0 to 150, 68 to 701, and 101 to 823, respectively. The total of these sugars (sucrose+glucose+fructose) ranged from 198 to 1543 mg/100 g FW. Concentrations of organic acids ranged from 0.0 (not detected) to 818, 430, 340, and 232 mg/100 g FW for citric, malic, fumaric, and succinic acids, respectively. However, the relative ranking in the concentrations of the individual acids was genotype-dependent. Total ascorbic-acid values ranged from 30 to 1466 mg/100 g FW. These data serve to document the range in the concentrations of individual sugars and acids present in mature C. chinense fruit and suggest that this variability may lend itself to studies involving the synthesis and/or metabolism of compounds associated with fruit flavor.

Pungency in Capsicum chinense: variation among countries of origin.

Fruits of 63 accessions of Capsicum chinense Jacq. from the USDA/ARS Capsicum germplasm collection were analyzed for two major capsaicinoids, capsaicin and dihydrocapsaicin, using gas chromatography with nitrogen phosphorus detection (GC/NPD). The objectives of the present investigation were: (i) to quantify the major capsaicinoids (capsaicin and dihydrocapsaicin) in fruits of Capsicum chinense accessions and (ii) to identify accessions containing great concentrations of capsaicinoids among countries of hot pepper origin. Seeds of C. chinense accessions received from Belize, Brazil, Colombia, Ecuador, Mexico, Peru, Puerto Rico, and United States were field grown in a silty-loam soil. Mature fruits were analyzed for major capsaicinoids content. Capsaicin concentrations were generally greater than dihydrocapsaicin. Fruits of C. chinense accession PI640900 (USA) contained the greatest concentration of capsaicin (1.52 mg g(- 1) fruit) and dihydrocapsaicin (1.16 mg g(- 1) fruit), while total major capsaicinoids in the fruits of PI438648 (Mexico) averaged 2 mg g(- 1) fruit. These two accessions were identified as potential candidates for mass production of major capsaicinoids that have health-promoting properties and for use as a source of pest control agents in agricultural fields.

Antioxidants in Capsicum chinense: variation among countries of origin.

The main objective of this investigation was to evaluate fruits of C. chinense accessions for their concentration of beta -carotene, ascorbic acid, and phenols for use as parents in breeding for these phytochemicals. Mature fruits of 63 accessions of C. chinense originally acquired from Belize, Brazil, Colombia, Ecuador, Mexico, Peru, Puerto Rico, and the United States were analyzed for their chemical composition. Fruits of C. chinense accessions PI-152452 (Brazil) and PI-360726 (Ecuador) contained the greatest concentrations of ascorbic acid (1.2 and 1.1 mg g(-1) fresh fruit, respectively), while PI-438648 (Mexico) contained the greatest concentration of total phenols content (349 micro g g(-1) fresh fruit) among the other 63 accessions tested. Accession PI-355817 from Ecuador contained the greatest concentrations of beta -carotene (8 mg g(-1)fresh fruit). These accessions were identified as potential candidates for mass production of antioxidants with health-promoting properties.

Antioxidants in hot pepper: variation among accessions.

The U.S. Department of Agriculture (USDA) pepper (Capsicum spp.) germplasm collection contains several thousand members or accessions. Many of these species and cultivars have not been analyzed for their concentrations of ascorbic acid, capsaicin, and total phenolic compounds, which are important antioxidants having a number of benefits for human health. The objective of this investigation was to select candidate accessions of hot pepper having high concentrations of ascorbic acid, capsaicin, free sugars, and total phenols for use as parents in breeding for these compounds. Seventeen accessions of pepper from the core Capsicum germplasm collection (four accessions of Capsicum chinense; five accessions of C. baccatum; six accessions of C. annuum; and two of C. frutescens) were field grown and their mature fruits were analyzed for their antioxidant composition. Concentrations of these compounds tended to be higher in C. chinense and C. baccatum, than in C. annuum and C. frutescens. Across all accessions the concentration of total phenols was correlated with ascorbic acid (r = 0.97) and free sugars (r = 0.80). Concentrations of total phenols (1.4, 1.3, and 1.3 mg g-1 fruit) and ascorbic acid (1.6, 1.2, and 1.3 mg g-1 fruit) were significantly greater in PI-633757, PI-387833, and PI-633754, respectively, compared to other accessions analyzed. Total capsaicinoids concentrations were greatest (1.3 mg g-1 fruit) in PI-438622 and lowest (0.002 mg g-1 fruit) in Grif-9320. The great variability within and among Capsicum species for these phytochemicals suggests that these selected accessions may be useful as parents in hybridization programs to produce fruits with value-added traits.

Screening Capsicum accessions for capsaicinoids content.

Ninety Capsicum accessions selected from the USDA Capsicum germplasm collection were screened for their capsaicinoids content using gas hromatography with nitrogen phosphorus detection (GC/NPD). Fresh fruits of Capsicum chinense, C. frutescens, C. baccatum, C. annuum, and C. pubescens were extracted with methanol and analyzed for capsaicin, dihydrocapsaicin, and nordihydrocapsaicin. Mass spectrometry of the fruit crude extracts indicated that the molecular ions at m/z 305, 307, and 293, which correspond to capsaicin, dihydrocapsaicin, and nordihydrocapsaicin, respectively, have a common benzyl cation fragment at m/z 137 that can be used for monitoring capsaicinoids in pepper fruit extracts. Capsaicin and dihydrocapsaicin were the dominant capsaicinoids detected. Capsaicin concentrations were typically greater than dihydrocapsaicin. Concentrations of total capsaicinoids varied from not detectable to 11.2 mg fruit(-1). Statistical analysis revealed that accession PI-441624 (C. chinense) had the highest capsaicin content (2.9 mg g(-1) fresh fruit) and accession PI-497984 (C. frutescens) had the highest dihydrocapsaicin content (2.3 mg g(-1) fresh fruit). Genebank accessions PI-439522 (C. frutescens) and PI-497984 contained the highest concentrations of total capsaicinoids.

Genetic discovery in Xylella fastidiosa through sequence analysis of selected randomly amplified polymorphic DNAs.

Xylella fastidiosa causes many important plant diseases including Pierce's disease (PD) in grape and almond leaf scorch disease (ALSD). DNA-based methodologies, such as randomly amplified polymorphic DNA (RAPD) analysis, have been playing key roles in genetic information collection of the bacterium. This study further analyzed the nucleotide sequences of selected RAPDs from X. fastidiosa strains in conjunction with the available genome sequence databases and unveiled several previously unknown novel genetic traits. These include a sequence highly similar to those in the phage family of Podoviridae. Genome comparisons among X. fastidiosa strains suggested that the "phage" is currently active. Two other RAPDs were also related to horizontal gene transfer: one was part of a broadly distributed cryptic plasmid and the other was associated with conjugal transfer. One RAPD inferred a genomic rearrangement event among X. fastidiosa PD strains and another identified a single nucleotide polymorphism of evolutionary value.