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About a mountain
When John D'Agata helps his mother move to Las Vegas one summer, he begins to follow a story about the federal government's plan to store high-level nuclear waste at Yucca Mountain, a desert range near the city of Las Vegas. Bearing witness to the parade of scientific, cultural, and political facts that give shape to Yucca's story, D'Agata keeps the six tenets of reporting in mind--Who, What, When, Where, Why, and How--arranging his own investigation around each vital question. Yet as the contradictions inherent in Yucca's story are revealed, D'Agata's investigation turns inevitably personal. He finds himself investigating the death of a teenager who jumps off the tower of the Stratosphere Hotel, a boy whom D'Agata believes he spoke with before his suicide. Here is the work of a penetrating thinker whose startling portrait of a mountain in the desert compels a reexamination of the future of human life.--From publisher description.
Book
Local Auxin Biosynthesis Mediated by a YUCCA Flavin Monooxygenase Regulates Haustorium Development in the Parasitic Plant Phtheirospermum japonicum
Parasitic plants in the Orobanchaceae cause serious agricultural problems worldwide. Parasitic plants develop a multicellular infectious organ called a haustorium after recognition of host-released signals. To understand the molecular events associated with host signal perception and haustorium development, we identified differentially regulated genes expressed during early haustorium development in the facultative parasite Phtheirospermum japonicum using a de novo assembled transcriptome and a customized microarray. Among the genes that were upregulated during early haustorium development, we identified YUC3, which encodes a functional YUCCA (YUC) flavin monooxygenase involved in auxin biosynthesis. YUC3 was specifically expressed in the epidermal cells around the host contact site at an early time point in haustorium formation. The spatio-temporal expression patterns of YUC3 coincided with those of the auxin response marker DR5, suggesting generation of auxin response maxima at the haustorium apex. Roots transformed with YUC3 knockdown constructs formed haustoria less frequently than nontransgenic roots. Moreover, ectopic expression of YUC3 at the root epidermal cells induced the formation of haustorium-like structures in transgenic P. japonicum roots. Our results suggest that expression of the auxin biosynthesis gene YUC3 at the epidermal cells near the contact site plays a pivotal role in haustorium formation in the root parasitic plant P. japonicum.
Journal Article
Floral scent of Joshua trees (Yucca brevifolia sensu lato): Divergence in scent profiles between species but breakdown of signal integrity in a narrow hybrid zone
PREMISE OF THE STUDY: The role of floral scent in facilitating reproductive isolation between closely related plants remains poorly understood. Yucca brevifolia and Yucca jaegeriana are pollinated by different moth species in allopatry, but in a narrow contact zone, pollinator-host specificity breaks down, resulting in hybridization between species. We explored the chemical basis for reproductive isolation and hybridization in these Joshua trees by characterizing the floral scent of each species in allopatry, analyzing scent profiles from trees in the contact zone, and matching these data with genotypic and phenotypic data. METHODS: We analyzed floral volatiles using gas chromatography-mass spectrometry, tested for species divergence of scent profiles and classified trees in the contact zone as hybrid or either parental species. We used floral and vegetative morphological data and genotypic data to classify trees and anatypes differed depending on which data set was used. KEY RESULTS: The Joshua tree floral scent included oxygenated 8-carbon compounds not reported for other yuccas. The two species differed (P < 0.001 ) in scent profiles. In the contact zone, many hybrids were found, and phenotypic traits were generally weakly correlated, which may be explained by extensive gene flow between species or by exposure to different selection pressures. CONCLUSIONS: Although the two Joshua tree species produce distinct floral scent profiles, it is insufficient to prevent attraction of associated pollinators to both hosts. Instead, floral morphology may be the key trait mediating gene flow between species.
Journal Article
Parasitism to mutualism continuum for Joshua trees inoculated with different communities of arbuscular mycorrhizal fungi from a desert elevation gradient
Most desert plants form symbiotic relationships with arbuscular mycorrhizal fungi (AMF), yet fungal identity and impacts on host plants remain largely unknown. Despite widespread recognition of the importance of AMF relationships for plant functioning, we do not know how fungal community structure changes across a desert climate gradient, nor the impacts of different fungal communities on host plant species. Because climate change can shape the distribution of species through effects on species interactions, knowing how the ranges of symbiotic partners are geographically structured and the outcomes of those species interactions informs theory and improves management recommendations. Here we used high throughput sequencing to examine the AMF community of Joshua trees along a climate gradient in Joshua Tree National Park. We then used a range of performance measures and abiotic factors to evaluate how different AMF communities may affect Joshua tree fitness. We found that fungal communities change with elevation resulting in a spectrum of interaction outcomes from mutualism to parasitism that changed with the developmental stage of the plant. Nutrient accumulation and the mycorrhizal growth response of Joshua tree seedlings inoculated with fungi from the lowest (warmest) elevations was first negative, but after 9 months had surpassed that of plants with other fungal treatments. This indicates that low elevation fungi are costly for the plant to initiate symbiosis, yet confer benefits over time. The strong relationship between AMF community and plant growth suggests that variation in AMF community may have long term consequences for plant populations along an elevation gradient.
Journal Article
Timing of rapid diversification and convergent origins of active pollination within Agavoideae (Asparagaceae)
PREMISE OF THE STUDY: Yucca species are ideal candidates for the study of coevolution due to the obligate mutualism they form with yucca moth pollinators (genera Tegeticula and Parategeticula). Yuccas are not the only species to exhibit a mutualism with yucca moths; the genus Hesperoyucca is pollinated by the California yucca moth (Tegeticula maculata). Relationships among yuccas, Hesperoyucca, and other members of subfamily Agavoideae are necessary to understand the evolution of this unique pollination syndrome. Here, we investigate evolutionary relationships of yuccas and closely related genera looking at the timing and origin of yucca moth pollination. METHODS: In this study, we sequenced the chloroplast genomes of 20 species in the subfamily Agavoideae (Asparagaceae) and three confamilial outgroup taxa to resolve intergeneric phylogenetic relationships of Agavoideae. We estimated divergence times using protein-coding genes from 67 chloroplast genomes sampled across monocots to determine the timing of the yucca moth pollination origin. KEY RESULTS: We confidently resolved intergeneric relationships in Agavoideae, demonstrating the origin of the yucca-yucca moth mutualism on two distinct lineages that diverged 27 million years ago. Comparisons of Yucca and Hesperoyucca divergence time to those of yucca moths (Tegeticula and Parategeticula, Prodoxidae) indicate overlapping ages for the origin of pollinating behavior in the moths and pollination by yucca moths in the two plant lineages. CONCLUSION: Whereas pollinating yucca moths have been shown to have a single origin within the Prodoxidae, there were independent acquisitions of active pollination on lineages leading to Yucca and Hesperoyucca within the Agavoideae.
Journal Article
Elucidation of the Metabolite Profile of Yucca gigantea and Assessment of Its Cytotoxic, Antimicrobial, and Anti-Inflammatory Activities
The acute inflammation process is explained by numerous hypotheses, including oxidative stress, enzyme stimulation, and the generation of pro-inflammatory cytokines. The anti-inflammatory activity of Yucca gigantea methanol extract (YGME) against carrageenan-induced acute inflammation and possible underlying mechanisms was investigated. The phytochemical profile, cytotoxic, and antimicrobial activities were also explored. LC-MS/MS was utilized to investigate the chemical composition of YGME, and 29 compounds were tentatively identified. In addition, the isolation of luteolin-7-O-β-d-glucoside, apigenin-7-O-β-d-glucoside, and kaempferol-3-O-α-l-rhamnoside was performed for the first time from the studied plant. Inflammation was induced by subcutaneous injection of 100 μL of 1% carrageenan sodium. Rats were treated orally with YGME 100, 200 mg/kg, celecoxib (50 mg/kg), and saline, respectively, one hour before carrageenan injection. The average volume of paws edema and weight were measured at several time intervals. Levels of NO, GSH, TNF-α, PGE-2, serum IL-1β, IL-6 were measured. In additionally, COX-2 immunostaining and histopathological examination of paw tissue were performed. YGME displayed a potent anti-inflammatory influence by reducing paws edema, PGE-2, TNF-α, NO production, serum IL-6, IL-1β, and COX-2 immunostaining. Furthermore, it replenished the diminished paw GSH contents and improved the histopathological findings. The best cytotoxic effect of YGME was against human melanoma cell line (A365) and osteosarcoma cell line (MG-63). Moreover, the antimicrobial potential of the extract was evaluated against bacterial and fungal isolates. It showed potent activity against Gram-negative, Gram-positive, and fungal Candida albicans isolates. The promoting multiple effects of YGME could be beneficial in the treatment of different ailments based on its anti-inflammatory, antimicrobial, and cytotoxic effects.
Journal Article
Yucca schidigera Extract Mitigates the Oxidative Damages, Inflammation, and Neurochemical Impairments in the Brains of Quails Exposed to Lead
The present study explored the neurotoxic impacts of lead (Pb) and the potential alleviating effect of Yucca schidigera extract (YSE) in Japanese quails. About 360 adult Japanese quails (8 weeks old) were used. Quails were randomly distributed to six groups with 4 replicates each: the control group (fed basal diet, BD), the BD + YSE1 and BD + YSE2 groups (BD + 100 and 200 mg/kg diet of YSE, respectively), the Pb group (BD + 100 mg/kg Pb), and the Pb + YSE1 and Pb + YSE2 groups (BD + Pb + 100 and 200 mg/kg YSE, respectively). This feeding trial lasted for 8 weeks. The exposure to Pb in the diet induced oxidative damage stress in the brain of exposed quails reflected by the significant increase in the oxidative markers including malonaldehyde (MDA) and protein carbonyl (PC) and the significant reduction in the activities of antioxidants including catalase (CAT), superoxide dismutase (SOD), and the reduced glutathione (GSH). Brain neurochemistry and enzyme activities were also altered following Pb exposure. Pb significantly reduced serotonin, dopamine, norepinephrine, GABA, Ach, and Na + /K + -ATPase activities. Pb dietary intoxication markedly increased brain inflammatory biomarkers, including tumor necrosis factor (TNF-α), myeloperoxidase, and nitric oxide. Peripherally, Pb toxicity decreased the amino acid neurotransmitters (glutamic acid, glycine, and aspartic acid) in the serum of birds. At the transcriptomic level, Pb exposure upregulated the transcription patterns of CASP3, TNF-α, HSP70, and IL-1β. The single effect of YSE maintained that all the assessed parameters were not changed compared to the control. Interestingly, the YSE co-supplementation with Pb alleviated the Pb-induced neuro-oxidative damages by lowering the lipid, protein, and DNA damage, and the inflammatory biomarkers.
Journal Article
Influence of dietary protein levels on nano-encapsulated Yucca schidigera extract and its effects on in vitro ruminal greenhouse gas production and fermentation dynamics
The influence of nano-encapsulated
Yucca schidigera
extract (YSE) on total gas (GP), ruminal methane (CH
4
), carbon monoxide (CO), hydrogen sulphide (H
2
S) production, and fermentation activities of diets based on two different protein levels were investigated. A completely randomized experimental design with a factorial arrangement (2 × 4 × 4) with three replications was used. Factor 1 was the dietary protein levels (14%and 18%), factor 2 was the types of extracts used (TE; negative control (without extract), positive control (empty chitosan nano-capsules),
Y. schidigera
extract nano-capsules, and crude
Y. schidigera
extract), and factor 3 the doses of each type of extract (ED; 0-, 0.25-, 0.5-, and 1.0- mL extract/g DM). Nano-chitosan reduced the GP production with a higher protein level by 24.9% after 48 h while the crude extract elevated it. At both crude protein levels, the interaction of crude extract at an ED of 0.25 mL extract/g DM generated a higher volume of CH
4
at 6 h (
p
= 0.001 and 0.001 respectively) compared to the volume generated by the negative control. The 0.25 mL extract/g DM extract for both the crude extract and nano-extract elicited higher and lower CO production at 6 h (
p
< 0.0001), respectively. Nano-chitosan at 0.25 mL extract/g DM resulted in less H
2
S produced at 6 h than when crude extract was used at the same dose and a higher protein level (
p
= 0.027). The ED did not significantly affect any of the parameters under consideration as used under lower protein levels. However, TE affected pH and dry matter degradability (
p
< 0.0001) while the interaction of both TE and ED impacted both CH
4
:SCFA and CH
4
:ME (
p
= 0.045) with higher and lower values obtained for nano-chitosan and the negative control, respectively. In conclusion, nano-chitosan at a higher protein level proved its antimicrobial property, and although the production of CO increased at 14% protein, in vitro fermentation indicated its ability to minimize the production of GP, methane and hydrogen sulphide in the rumen, and to boost the degradability of DM and methane conversion efficiency.
Journal Article
Mojave Yucca (Yucca Schidigera Roezl) Effects on Female Reproduction a Review
Yucca is an important source of biologically active substances such as steroidal saponins and stilbenes providing many beneficial effects when administered to humans and other animals. These substances offer a great potential in the prevention and treatment of current civilized diseases as well as to their: antioxidant, hypocholesterolaemic, anti-inflammatory, phytoestrogenic, pro-apoptotic, anti-proliferative, and anti-carcinogenic properties. This review focuses on the roles of two main yucca constituent groups and their ability to modulate ovarian functions and female reproductive performance. Both the biological activity of yucca substances and the mechanisms of their actions on ovaries are still incompletely understood. Thus, the direct effects of yucca extract on ovarian cells in animal models under in vitro conditions, as well as actions after yucca consumption will be discussed.
Journal Article
Population genomics of divergence within an obligate pollination mutualism: Selection maintains differences between Joshua tree species
PREMISE OF THE STUDY: Speciation is a complex process that can be shaped by many factors, from geographic isolation to interspecific interactions. In Joshua trees, selection from pollinators on style length has been hypothesized to contribute to the maintenance of differentiation between two hybridizing sister species. We used population genomics approaches to measure the extent of genetic differentiation between these species, test whether selection maintains differences between them, and determine whether genetic variants associated with style length show signatures of selection. METHODS: Using restriction-site-associated DNA (RAD)-sequencing, we identified 9516 single nucleotide polymorphisms (SNPs) across the Joshua tree genome. We characterized the genomic composition of trees in a narrow hybrid zone and used genomic scans to search for signatures of selection acting on these SNPs. We used a genome-wide association study to identify SNPs associated with variation in phenotypic traits, including style length, and asked whether those SNPs were overrepresented among the group under selection. KEY RESULTS: The two species were highly genetically differentiated (FST = 0.25), and hybrids were relatively rare in the hybrid zone. Approximately 20% of SNPs showed evidence of selection maintaining divergence. While SNPs associated with style length were overrepresented among those under selection (P << 0.0001), the same was true for SNPs associated with highly differentiated vegetative traits. CONCLUSIONS: The two species of Joshua tree are clearly genetically distinct, and selection is maintaining differences between them. We found that loci associated with differentiated traits were likely to be under selection. However, many traits other than style length appeared to be under selection. Together with the dearth of intermediate hybrids, these findings reveal that these taxa are more strongly diverged than previously suspected and that selection, likely on many targets, is maintaining separation where the two species meet and hybridize.
Journal Article