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-1ß. 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.

Genome-Wide Identification, Expression Analysis, and Potential Roles under Abiotic Stress of the YUCCA Gene Family in Mungbean (Vigna radiata L.).

YUCCA, belonging to the class B flavin-dependent monooxygenases, catalyzes the rate-limiting step for endogenous auxin synthesis and is implicated in plant-growth regulation and stress response. Systematic analysis of the YUCCA gene family and its stress response benefits the dissection of regulation mechanisms and breeding applications. In this study, 12 YUCCA genes were identified from the mungbean (Vigna radiata L.) genome and were named based on their similarity to AtYUCCAs. Phylogenetic analysis revealed that the 12 VrYUCCAs could be divided into 4 subfamilies. The evidence from enzymatic assays in vitro and transgenetic Arabidopsis in vivo indicated that all the isolated VrYUCCAs had biological activity in response to IAA synthesis. Expression pattern analysis showed that functional redundancy and divergence existed in the VrYUCCA gene family. Four VrYUCCAs were expressed in most tissues, and five VrYUCCAs were specifically highly expressed in the floral organs. The response toward five stresses, namely, auxin (indole-3-acetic acid, IAA), salinity, drought, high temperatures, and cold, was also investigated here. Five VrYUCCAs responded to IAA in the root, while only VrYUCCA8a was induced in the leaf. VrYUCCA2a, VrYUCCA6a, VrYUCCA8a, VrYUCCA8b, and VrYUCCA10 seemed to dominate under abiotic stresses, due to their sensitivity to the other four treatments. However, the response modes of the VrYUCCAs varied, indicating that they may regulate different stresses in distinct ways to finely adjust IAA content. The comprehensive analysis of the VrYUCCAs in this study lays a solid foundation for further investigation of VrYUCCA genes' mechanisms and applications in breeding.

Genome-Wide Identification and Characterization of YUCCA Gene Family in Mikania micrantha.

Auxin is a general coordinator for growth and development throughout plant lifespan, acting in a concentration-dependent manner. Tryptophan aminotransferases (YUCCA) family catalyze the oxidative decarboxylation of indole-3-pyruvic acid (IPA) to form indole-3-acetic acid (IAA) and plays a critical role in auxin homeostasis. Here, 18 YUCCA family genes divided into four categories were identified from Mikania micrantha (M. micrantha), one of the world's most invasive plants. Five highly conserved motifs were characterized in these YUCCA genes (MmYUCs). Transcriptome analysis revealed that MmYUCs exhibited distinct expression patterns in different organs and five MmYUCs showed high expression levels throughout all the five tissues, implying that they may play dominant roles in auxin biosynthesis and plant development. In addition, MmYUC6_1 was overexpressed in DR5::GUS Arabidopsis line to explore its function, which resulted in remarkably increased auxin level and typical elevated auxin-related phenotypes including shortened roots and elongated hypocotyls in the transgenic plants, suggesting that MmYUC6_1 promoted IAA biosynthesis in Arabidopsis. Collectively, these findings provided comprehensive insight into the phylogenetic relationships, chromosomal distributions, expression patterns and functions of the MmYUC genes in M. micrantha, which would facilitate the study of molecular mechanisms underlying the fast growth of M. micrantha and preventing its invasion.

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-ß-d-glucoside, apigenin-7-O-ß-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-1ß, 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-1ß, 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.

Identification, analysis, and modeling of the YUCCA protein family genome-wide in Coffea canephora.

Auxin is involved in almost every aspect of plant growth and development, from embryogenesis to senescence. Indole-3-acetic acid (IAA) is the main known natural auxin that is synthesized by enzymes tryptophan aminotransferase of arabidopsis (TAA) and YUCCA (YUC) of the flavin-containing monooxygenases family (FMO) from one of the tryptophan-dependent pathways. Genome-wide identification and comprehensive analysis of the YUC-protein family have been conducted in Coffea canephora in the present study. A total of 10 members CcYUC gene family were identified in C. canephora. Phylogenetic analysis revealed that the CcYUC protein family is evolutionarily conserved, and they consist of four groups. In contrast, bioinformatic analysis predicted a hydrophobic transmembrane helix (TMH) for one CcYUC (YUC10) member only. Isoelectric point (pI), molecular mass (Ms), signal peptide, subcellular localization, and phosphorylation sites were predicted for CcYUC proteins. YUC enzymes require the prosthetic group flavin adenine dinucleotide (FAD) and the cofactor nicotinamide adenine dinucleotide phosphate (NADPH) for their enzymatic activity. Therefore, we include the molecular docking for CcYUC2-FAD-NADPH-IPyA and yucasin, which is a specific inhibitor for YUC activity. The docking results showed FAD and NADPH binding at the big and small domain sites, respectively, in CcYUC2. IPyA binds very close to FAD along the big domain, and yucasin competes for the same site as IPA, blocking IAA production. Furthermore, in silico point mutations affect the stability of the CcYUC2-4 proteins.

Tetranorsesquiterpenoids as Attractants of Yucca Moths to Yucca Flowers.

The obligate pollination mutualism between Yucca and yucca moths is a classical example of coevolution. Oviposition and active pollination by female yucca moths occur at night when Yucca flowers are open and strongly scented. Thus, floral volatiles have been suggested as key sensory signals attracting yucca moths to their host plants, but no bioactive compounds have yet been identified. In this study, we showed that both sexes of the pollinator moth Tegeticula yuccasella are attracted to the floral scent of the host Yucca filamentosa. Chemical analysis of the floral headspace from six Yucca species in sections Chaenocarpa and Sarcocarpa revealed a set of novel tetranorsesquiterpenoids putatively derived from (E)-4,8-dimethyl-1,3,7-nonatriene. Their structure elucidation was accomplished by NMR analysis of the crude floral scent sample of Yucca treculeana along with GC/MS analysis and confirmed by total synthesis. Since all these volatiles are included in the floral scent of Y. filamentosa, which has been an important model species for understanding the pollination mutualism, we name these compounds filamentolide, filamentol, filamental, and filamentone. Several of these compounds elicited antennal responses in pollinating (Tegeticula) and non-pollinating (Prodoxus) moth species upon stimulation in electrophysiological recordings. In addition, synthetic (Z)-filamentolide attracted significant numbers of both sexes of two associated Prodoxus species in a field trapping experiment. Highly specialized insect-plant interactions, such as obligate pollination mutualisms, are predicted to be maintained through "private channels" dictated by specific compounds. The identification of novel bioactive tetranorsesquiterpenoids is a first step in testing such a hypothesis in the Yucca-yucca moth interaction.

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.

Antibacterial activity of phellodendron bark against Streptococcus mutans.

Streptococcus mutans is a major cause of tooth decay due to its promotion of biofilm formation and acid production. Several plant extracts have been reported to have multiple biological activities such as anti-inflammation and antibacterial effects. This study investigated the antibacterial activity of three plant extracts, phellodendron bark (PB), yucca, and black ginger, and found that PB had a stronger effect than the other extracts. Then, the minimum inhibitory concentration (MIC) of PB against 100 S. mutans strains was investigated. The MIC range of PB was 9.8-312.5 µg/mL. PB suppressed the growth kinetics of S. mutans in a dose-dependent manner, even at sub-MICs of PB. Then, we investigated the effect of PB on S. mutans virulence. The PB suppressed biofilm formation at high concentrations, although PB did not affect the expression of glucosyltransferase genes. Additionally, PB suppressed the decrease in pH from adding an excess of glucose. The expression of genes responsible for acid production was increased by the addition of excess glucose without PB, whereas their expression levels were not increased in the presence of 1× and 2× MIC of PB. Although PB showed a bacteriostatic effect on planktonic S. mutans cells, it was found that more than 2× MIC of PB showed a partial bactericidal effect on biofilm cells. In conclusion, PB not only showed antibacterial activity against S. mutans but also decreased the cariogenic activity in S. mutans.

The Pattern of Straight Chain Hydrocarbons Released by Yucca Flowers (Asparagaceae).

The hydrocarbon pattern in the floral scent of Yucca species was found to comprise a group of unbranched, mid-chain alkanes, alkenes, and an alkadiene. In Y. reverchonii, highly dominant (Z)-8-heptadecene is accompanied by (6Z,9Z)-6,9-heptadecadiene and heptadecane as minor components and by traces of other saturated and unsaturated hydrocarbons with similar chain length. Some of these volatiles proved to be perceived by the antennae of Tegeticula cassandra (pollinating seed-eater of Yucca) and Prodoxus decipiens (herbivore on Yucca). The possible biosynthesis of the compounds is discussed.

Transcript profiling of a novel plant meristem, the monocot cambium.

While monocots lack the ability to produce a vascular cambium or woody growth, some monocot lineages evolved a novel lateral meristem, the monocot cambium, which supports secondary radial growth of stems. In contrast to the vascular cambium found in woody angiosperm and gymnosperm species, the monocot cambium produces secondary vascular bundles, which have an amphivasal organization of tracheids encircling a central strand of phloem. Currently there is no information concerning the molecular genetic basis of the development or evolution of the monocot cambium. Here we report high-quality transcriptomes for monocot cambium and early derivative tissues in two monocot genera, Yucca and Cordyline. Monocot cambium transcript profiles were compared to those of vascular cambia and secondary xylem tissues of two forest tree species, Populus trichocarpa and Eucalyptus grandis. Monocot cambium transcript levels showed that there are extensive overlaps between the regulation of monocot cambia and vascular cambia. Candidate regulatory genes that vary between the monocot and vascular cambia were also identified, and included members of the KANADI and CLE families involved in polarity and cell-cell signaling, respectively. We suggest that the monocot cambium may have evolved in part through reactivation of genetic mechanisms involved in vascular cambium regulation.

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 analyzed whether certain trait combinations were more correlated than others with respect to assignment of trees and whether frequencies of classified tree types 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.

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.

The use of Yucca schidigera and microbial preparation for poultry manure deodorization and hygienization.

The aim of this study was to determine the effectiveness of microbial preparation and Yucca schidigera in the removal of odorous volatile compounds from poultry manure as well as to evaluate antimicrobial properties of these amendments. It was demonstrated that the combined treatment of poultry manure (PM) with the microbial preparation and Y. schidigera extract can reduce the concentration of odorants by 58%-73%, depending on the tested compound. When Y. schidigera extract and the microbial preparation were applied at a time interval of 48 h, the deodorization efficiency was improved by 6-24%. Furthermore, Y. schidigera extract has antimicrobial properties, which affect poultry manure hygienization. It was found that when the microbial preparation was enriched with Lactobacillus plantarum, it became insensitive to the antimicrobial properties of Y. schidigera.

Gas exchange and leaf anatomy of a C3-CAM hybrid, Yucca gloriosa (Asparagaceae).

While the majority of plants use the typical C3 carbon metabolic pathway, ~6% of angiosperms have adapted to carbon limitation as a result of water stress by employing a modified form of photosynthesis known as Crassulacean acid metabolism (CAM). CAM plants concentrate carbon in the cells by temporally separating atmospheric carbon acquisition from fixation into carbohydrates. CAM has been studied for decades, but the evolutionary progression from C3 to CAM remains obscure. In order to better understand the morphological and physiological characteristics associated with CAM photosynthesis, phenotypic variation was assessed in Yucca aloifolia, a CAM species, Yucca filamentosa, a C3 species, and Yucca gloriosa, a hybrid species derived from these two yuccas exhibiting intermediate C3-CAM characteristics. Gas exchange, titratable leaf acidity, and leaf anatomical traits of all three species were assayed in a common garden under well-watered and drought-stressed conditions. Yucca gloriosa showed intermediate phenotypes for nearly all traits measured, including the ability to acquire carbon at night. Using the variation found among individuals of all three species, correlations between traits were assessed to better understand how leaf anatomy and CAM physiology are related. Yucca gloriosa may be constrained by a number of traits which prevent it from using CAM to as high a degree as Y. aloifolia. The intermediate nature of Y. gloriosa makes it a promising system in which to study the evolution of CAM.

Inclusion of Yucca schidigera and zeolite in dog feed: influence on mineral excretion / Inclusão de Yucca schidigera e zeólita em alimentos para cães: influência sobre a excreção de minerais

This study aimed to evaluate the effects of adding Yucca schidigera and zeolite (Clinoptilolite) to feed (super premium and standard) for adult dogs on the apparent indigestibility coefficient of minerals. In the first assessment, 21 dogs were used, with average weight of 12.5kg±1.46 in seven treatments in two periods (super premium diet referred to as control and control with the addition of 125, 250, 375ppm Yucca schidigera and 0.5%, 0.75% and 1.0% zeolite). The second assessment was conducted with standard feed, using 21 experimental plots distributed in three treatments (standard diet referred to as control and control with the addition of 375ppm of Yucca schidigera and 1.0% zeolite). The additives did not affect the acceptability of feed and fecal characteristics in both assessments (P>0.05). With the exception of calcium, no minerals were affected by the inclusion of additives (P>0.05) in the experiment with super premium feed. In the assessment with standard feed, calcium as phosphorus and magnesium presented decreased excretion (P<0.05) with the inclusion of additives. It is possible to conclude that the inclusion of additives in the tested concentrations may interfere with the excretion of some minerals in the diet.

Este trabalho teve como objetivo avaliar os efeitos da inclusão de Yucca schidigera e zeólita (Clinoptilolita) em alimentos (super premium e standard) para cães adultos sobre o coeficiente de indigestibilidade aparente de minerais. No primeiro ensaio, foram utilizados 21 cães, com peso médio de 12,5kg±1,46, distribuídos em sete tratamentos em dois períodos (dieta super premium denominada controle e controle com adição de 125, 250, 375ppm de Yucca schidigera e 0,5%, 0,75% e 1,0% de zeólita). O segundo foi realizado com um alimento standard, utilizando-se 21 parcelas experimentais distribuídas em três tratamentos (dieta standard denominada controle e controle com adição de 375ppm de Yucca schidigera e 1,0% de zeólita). Os aditivos não afetaram a aceitabilidade do alimento e as características fecais nos dois ensaios (P>0,05). Com exceção do cálcio, nenhum mineral sofreu interferência da inclusão dos aditivos (P>0,05) no experimento com alimento super premium. No ensaio com alimento standard, tanto cálcio quanto fósforo e magnésio apresentaram redução na excreção (P<0,05) com a inclusão dos aditivos. Pôde-se concluir que a inclusão dos aditivos nas concentrações testadas pode interferir na excreção de alguns minerais da dieta.

Yucca schidigera extract--a bioresource for the reduction of ammonia from mariculture.

Extract of a desert plant, Yuccaschidigera (YUPE) at 0 mg L(-1) (control), 18, 36 and 72 mg L(-1) was added to seawater containing 30, 50 and 100 Kuruma shrimp Marsupenaeusjaponicus postlarvae (PL) per liter with or without aeration for 24h to study its effects on reducing ammonia excreted from the PL. Even at the lowest YUPE addition level and the highest PL density, no ammonia accumulated in both aerated and no-aerated set-ups for up to 12h. Ammonia accumulated only in the controls. YUPE showed more effective in reducing ammonia in seawater from this biogenic source than ammonia from chemical source used in previous studies. Consequently, YUPE is identified as a natural, safe, and effective solution for ammonia reduction in seawater and mariculture.

[Ultrastructural study of TNT effect on the callus cells and the cells of intact plants of Yucca gloriosa L].

Intracellular distribution of assimilated 2,4,6-trinitrotoluene (TNT) in callus cells, flower buds and leaves of intact Yucca gloriosa L. plants using electron microscope radioautography. The radiotracer was detected in vacuoles, plastids, mitochondrion, endoplasmic reticulum and cytoplasm. It was found that in dedifferentiated callus cells TNT was incorporated in the vacuoles in greater quantities in comparison with the cells of intact plant. Correspondingly the ultrastructural integrity of the dedifferentiated cells is less damaged.

Feeding saponin-containing Yucca schidigera and Quillaja saponaria to decrease enteric methane production in dairy cows.

An experiment was conducted in vitro to determine whether the addition of saponin-containing Yucca schidigera or Quillaja saponaria reduces methane production without impairing ruminal fermentation or fiber digestion. A slightly lower dose of saponin was then fed to lactating dairy cows to evaluate effects on ruminal fermentation, methane production, total-tract nutrient digestibility, and milk production and composition. A 24-h batch culture in vitro incubation was conducted in a completely randomized design with a control (no additive, CON) and 3 doses of either saponin source [15, 30, and 45 g/kg of substrate dry matter (DM)] using buffered ruminal fluid from 3 dairy cows. The in vivo study was conducted as a crossover design with 2 groups of cows, 3 treatments, and three 28-d periods. Six ruminally cannulated cows were used in group 1 and 6 intact cows in group 2 (627 +/- 55 kg of body weight and 155 +/- 28 d in milk). The treatments were 1) early lactation total mixed ration, no additive (control; CON); 2) CON diet supplemented with whole-plant Y. schidigera powder at 10 g/kg of DM (YS); and 3) CON diet supplemented with whole-plant Q. saponaria powder at 10 g/kg of DM (QS). Methane production was measured in environmental chambers and with the sulfur hexafluoride (SF(6)) tracer technique. In vitro, increasing levels of both saponin sources decreased methane concentration in the headspace and increased the proportion of propionate in the buffered rumen fluid. Concentration of ammonia-N, acetate proportion, and the acetate:propionate ratio in the buffered rumen fluid as well as 24-h digestible neutral detergent fiber were reduced compared with the CON treatment. Medium and high saponin levels decreased DM digestibility compared with the CON treatment. A lower feeding rate of both saponin sources (10 g/kg of DM) was used in vivo in an attempt to avoid potentially negative effects of higher saponin levels on feed digestibility. Feeding saponin did not affect milk production, total-tract nutrient digestibility, rumen fermentation, or methane production. However, DM intake was greater for cows fed YS and QS than for CON cows, with a tendency for greater DM intake for cows fed YS compared with those fed QS. Consequently, efficiency of milk production (kg of milk/kg of DM intake) was lower for cows fed saponin compared with controls. The results show that although saponin from Y. schidigera and Q. saponaria lowered methane production in vitro, the reduction was largely due to reduced ruminal fermentation and feed digestion. Feeding a lower dose of saponin to lactating dairy cows avoided potentially negative effects on ruminal fermentation and feed digestion, but methane production was not reduced. Lower efficiency of milk production of cows fed saponin, and potential reductions in feed digestion at high supplementation rates may make saponin supplements an unattractive option for lowering methane production in vivo.

Local auxin production: a small contribution to a big field.

Auxin is a plant growth regulator involved in diverse fundamental developmental responses. Much is now known about auxin transport, via influx and efflux carriers, and about auxin perception and its role in gene regulation. Many developmental processes are dependent on peaks of auxin concentration and, to date, attention has been directed at the role of polar auxin transport in generating and maintaining auxin gradients. However, surprisingly little attention has focussed on the role and significance of auxin biosynthesis, which should be expected to contribute to active auxin pools. Recent reports on the function of the YUCCA flavin monooxygenases and a tryptophan aminotransferase in Arabidopsis have caused us to look again at the importance of local biosynthesis in developmental processes. Many alternative and redundant pathways of auxin synthesis exist in many plants and it is emerging that they may function in response to environmental cues.