Cyanogenic Glucosides Research Articles

Transcript profiles of wild and domesticated sorghum under water-stressed conditions and the differential impact on dhurrin metabolism

Main conclusionAustralian native species of sorghum contain negligible amounts of dhurrin in their leaves and the cyanogenesis process is regulated differently under water-stress in comparison to domesticated sorghum species.Cyanogenesis in forage sorghum is a major concern in agriculture as the leaves of domesticated sorghum are potentially toxic to livestock, especially at times of drought which induces increased production of the cyanogenic glucoside dhurrin. The wild sorghum species endemic to Australia have a negligible content of dhurrin in the above ground tissues and thus represent a potential resource for key agricultural traits like low toxicity. In this study we investigated the differential expression of cyanogenesis related genes in the leaf tissue of the domesticated species Sorghum bicolor and the Australian native wild species Sorghum macrospermum grown in glasshouse-controlled water-stress conditions using RNA-Seq analysis to analyse gene expression. The study identified genes, including those in the cyanogenesis pathway, that were differentially regulated in response to water-stress in domesticated and wild sorghum. In the domesticated sorghum, dhurrin content was significantly higher compared to that in the wild sorghum and increased with stress and decreased with age whereas in wild sorghum the dhurrin content remained negligible. The key genes in dhurrin biosynthesis, CYP79A1, CYP71E1 and UGT85B1, were shown to be highly expressed in S. bicolor. DHR and HNL encoding the dhurrinase and α-hydroxynitrilase catalysing bio-activation of dhurrin were also highly expressed in S. bicolor. Analysis of the differences in expression of cyanogenesis related genes between domesticated and wild sorghum species may allow the use of these genetic resources to produce more acyanogenic varieties in the future.

Neurobehavioral and Ameliorative Effect of Complan Milk and Bambara Nut on Rats Fed With Bitter Cassava – A Nutritional Approach

Cassava products have been introduced to the market in different regions of the world as part of diet, despite containing more than one toxic substance. Roots and leaves of cassava of all varieties contain cyanogenic glucoside, mainly as linamarin, but also as lotaustralin, in different concentrations in their cellular vacuoles. Twenty (20) albino Wistar rats were used for this research and were randomly selected into 4 groups of five 5 rats each. The result obtained from the study showed that there was a significant reduction in weight of the Konzo induced Wistar rats group from week 1 to week 4. A weight gain of 21.7g to 34.7g was observed in the cassava-induced Konzo and complan milk fed group Wistar rats and cassava-induced Konzo and Bambara nut (Okpa) fed group Wistar rats when compared with the cassava-induced Konzo group Wistar rats. There was a decrease in Na+,K+, Urea, Creatinine and HCO3 in cassava-induced Konzo and Bambara nut (Okpa) fed group Wistar rats when compared with cassava-induced Konzo Wistar rat group and control group. In evaluating the motor coordination/impairment using rotarod test, cassava-induced Konzo Wistar rat group, cassava-induced Konzo and complan milk fed group Wistar rats group and cassava-induced Konzo and Bambara nut (Okpa) fed Wistar rats group spent a significantly less mean time 20.65±0.33, 24.93±0.67 and 25.71±0.72 respectively when compared to the control group mean time of 39.45±0.42. Also, a significant improvement in motor coordination was observed in cassava-induced Konzo and complan milk fed group Wistar rats group and cassava-induced Konzo and Bambara nut (Okpa) fed Wistar rats group when compared with cassava-induced Konzo Wistar rat group. From the histological evaluation of the brain of the Wistar rats showed neurons that are vacuolated as a result of bitter cassava and alpha motor neurons. It is hence concluded that the toxic effect of bitter cassava can be ameliorated using proteins or balanced diets such as milk and bambara nuts (Okpa).

Agronomical and breeding approaches to improve the nutritional status of forage crops for better livestock productivity

AbstractBalanced feeding to livestock can effectively convert the non‐edible forage crops into human food. Balanced output and input feeding systems further will result in greater animal health and production outcomes, with greater capacity to support growing global food demands. It also positively impacts the global economy and livelihood support of those entirely depending on livestock rearing. In general, plants are made up of carbohydrates, proteins, lipids, fibres, lignin, minerals and vitamins of varying concentrations. These nutritional components in forage crops are key determinants of livestock growth, reproduction, behaviour, productivity and end‐product quality (milk and meat etc.). A high proportion of lignin, undigested fibres, and anti‐nutritional factors (cyanogenic glucosides, Hydrogen cyanide (HCN) and condensed tannins) adversely affect the nutritional quality of forage crops. This review highlighted the importance of nutritional and anti‐nutritional components and their inter‐relationship with diverse agro‐climatic conditions. Further, we tried to cover the recent agronomical, conventional and non‐conventional breeding methods to improve the nutritional quality of forage crops concerning livestock productivity.

Cyanogenesis in the Sorghum Genus: From Genotype to Phenotype.

Domestication has resulted in a loss of genetic diversity in our major food crops, leading to susceptibility to biotic and abiotic stresses linked with climate change. Crop wild relatives (CWR) may provide a source of novel genes potentially important for re-gaining climate resilience. Sorghum bicolor is an important cereal crop with wild relatives that are endemic to Australia. Sorghum bicolor is cyanogenic, but the cyanogenic status of wild Sorghum species is not well known. In this study, leaves of wild species endemic in Australia are screened for the presence of the cyanogenic glucoside dhurrin. The direct measurement of dhurrin content and the potential for dhurrin-derived HCN release (HCNp) showed that all the tested Australian wild species were essentially phenotypically acyanogenic. The unexpected low dhurrin content may reflect the variable and generally nutrient-poor environments in which they are growing in nature. Genome sequencing of six CWR and PCR amplification of the CYP79A1 gene from additional species showed that a high conservation of key amino acids is required for correct protein function and dhurrin synthesis, pointing to the transcriptional regulation of the cyanogenic phenotype in wild sorghum as previously shown in elite sorghum.

Seedling growth and fall armyworm feeding preference influenced by dhurrin production in sorghum

Cyanogenic glucosides (CGs) play a key role in host-plant defense to insect feeding; however, the metabolic tradeoffs between synthesis of CGs and plant growth are not well understood. In this study, genetic mutants coupled with nondestructive phenotyping techniques were used to study the impact of the CG dhurrin on fall armyworm [Spodoptera frugiperda (J.E. Smith)] (FAW) feeding and plant growth in sorghum [Sorghum bicolor (L.) Moench]. A genetic mutation in CYP79A1 gene that disrupts dhurrin biosynthesis was used to develop sets of near-isogenic lines (NILs) with contrasting dhurrin contents in the Tx623 bmr6 genetic background. The NILs were evaluated for differences in plant growth and FAW feeding damage in replicated greenhouse and field trials. Greenhouse studies showed that dhurrin-free Tx623 bmr6 cyp79a1 plants grew more quickly than wild-type plants but were more susceptible to insect feeding based on changes in green plant area (GPA), total leaf area, and total dry weight over time. The NILs exhibited similar patterns of growth in field trials with significant differences in leaf area and dry weight of dhurrin-free plants between the infested and non-infested treatments. Taken together, these studies reveal a significant metabolic tradeoff between CG biosynthesis and plant growth in sorghum seedlings. Disruption of dhurrin biosynthesis produces plants with higher growth rates than wild-type plants but these plants have greater susceptibility to FAW feeding.

Factors Affecting the Utilisation of Cassava Products for Poultry Feeding [Review

Short supply and high cost of traditional ingredients affect efficientlivestock production globally. This has driven interest in alternative cheap materials mostly products of agro-industrial processing to replace traditional feed ingredients. Products such as discarded roots, leaf, peel and pulp are wasted or dumped in landfills in many developing regions, which could replace part of the expensive feed ingredients in livestock feeding. Cassava (Manihot esculenta Crantz) processing emitsseveral products such as peel, pulp and leaves. The sebeneficial cassava products are underutilised and more investigation is warranted to improve its utilisation, reduce feed cost and environment sustainability. Cassava peel, pulp and leaves are potential cheap feed ingredients for poultry feeding. However, these productsmay contain anti-nutritional factors such as cyanogenic glucosides which affect their maximum utilisation in poultry feeding. Several factors such as cultivar, stage of maturity, cyanide levels and processing methods affect the utilisation of cassava products in poultry diets. Several processing techniques have been used to reduce cyanogenic glucosides concentration to safe levels and enhance the utilisation of the products in poultry diets. This paper discusses the anti-nutritional factors affecting cassava utilisation, processing methods toreduce cyanide levels and future of cassava products for poultry feeding.

Exploring the possibilities of some selected flour blends for the development of bakery products: Comparison with some physicochemical and functional properties of wheat flour.

This study explored the possibilities of some selected flour blends vis-a-vis the physicochemical and functional properties of wheat flour. Ten flour blends from potato starch, cassava, maize and soybean flours and wheat flour were made and evaluated for physicochemical, functional and anti-nutritional properties. The range of proximate values were for moisture (3.76%-6.67%), protein (4.33-8.96%), ash (1.35-1.96%), fat (3.37-4.88%), fibre (1.22-1.89%) and carbohydrate (78.35-84.94%), whereas wheat flour had moisture (9.45%), protein (11.31%), ash (2.54%), fat (3.78%), fibre (1.31%) and carbohydrate (73.90%). Cyanogenic glucoside, saponion and tannin contents increased with increase substitution of cassava and soybean flours. Pasting temperatures of flour blends ranged from 69.03 °C to 78.83 °C, while wheat flour had 78.05 °C. Peak, hot paste, breakdown, setback and cold paste viscosities were 1514-2822, 1036-1597, 487-1225, 580-884 and 1616-2461 cp in flour blends compared to 2361, 1360, 1001, 1079 and 2439 cp of wheat flour. Substitutions with soy flour decreased the peak, hot paste, breakdown and cold paste viscosities but increased the pasting temperatures. L*, a* and b* values ranged from 78.56 to 87.65, -0.34 to 0.71 and 10. 95 to 13.50 in flour blends while the wheat flour varied significantly at 2361.00, 1360.00 and 1001.00. The nutritional and pasting properties of some of flour blends were closely related to wheat flour and may be used for bakery requirements.

Regulation of dhurrin pathway gene expression during Sorghum\xa0bicolor development

Main conclusionDevelopmental and organ-specific expression of genes in dhurrin biosynthesis, bio-activation, and recycling offers dynamic metabolic responses optimizing growth and defence responses in Sorghum.Plant defence models evaluate the costs and benefits of resource investments at different stages in the life cycle. Poor understanding of the molecular regulation of defence deployment and remobilization hampers accuracy of the predictions. Cyanogenic glucosides, such as dhurrin are phytoanticipins that release hydrogen cyanide upon bio-activation. In this study, RNA-seq was used to investigate the expression of genes involved in the biosynthesis, bio-activation and recycling of dhurrin in Sorghum bicolor. Genes involved in dhurrin biosynthesis were highly expressed in all young developing vegetative tissues (leaves, leaf sheath, roots, stems), tiller buds and imbibing seeds and showed gene specific peaks of expression in leaves during diel cycles. Genes involved in dhurrin bio-activation were expressed early in organ development with organ-specific expression patterns. Genes involved in recycling were expressed at similar levels in the different organ during development, although post-floral initiation when nutrients are remobilized for grain filling, expression of GSTL1 decreased > tenfold in leaves and NITB2 increased > tenfold in stems. Results are consistent with the establishment of a pre-emptive defence in young tissues and regulated recycling related to organ senescence and increased demand for nitrogen during grain filling. This detailed characterization of the transcriptional regulation of dhurrin biosynthesis, bioactivation and remobilization genes during organ and plant development will aid elucidation of gene regulatory networks and signalling pathways that modulate gene expression and dhurrin levels. In-depth knowledge of dhurrin metabolism could improve the yield, nitrogen use efficiency and stress resilience of Sorghum.

Production of bioethanol from wild cassava crude starch (Manihot glaziovii Muell. Arg) using different microbial types and fermentation times

Wild cassava (Manihot glaziovii Muell. Arg) is one of the varieties of cassava that contains toxic compounds cyanogenic glucosides, which cause unmarketable food products more suitable to be processed into bioethanol. This wild cassava plant produces tubers four times in weight compared to that of ordinary cassava, and the flesh contains about 40–70% starch by dry weight. This study aimed to determine the effect of the microbial types and fermentation times on bioethanol production from M. glaziovii Muell. Arg crude starch and to determine the type of microbes and fermentation time that can produce the highest bioethanol product from M. glaziovii Muell. Arg crude starch. This study consists of two factors using a factorial randomized block design (RBD). The first factor was the type of microbe which consists of 2 different microbes, namely R5I3 isolates and Saccharomyces cerevisiae ATCC 9763. The second factor was the fermentation time which consists of 4 levels, namely 3, 4, 5 and 6 days. The observed parameters were total dissolved solids value, pH value, reducing sugar content, and ethanol content. The data obtained were analyzed using analysis of variance (ANOVA) and continued with Tukey’s HSD post hoc tests. The results showed that fermentation using R5I3 isolates with a fermentation time of 5 days was the best treatment to obtain a maximum ethanol of 21.64±3.03 g/L, with a final pH value of 4.70±0.14, total dissolved solids 4.10±0.14°Brix and reducing sugar content of 0.91±0.02 g/L. Therefore, the new isolate R513 was highly potential for producing bioethanol from wild cassava crude starch.

Dual-species origin of an adaptive chemical defense polymorphism.

Allopolyploid speciation and chemical defense diversification are two of the most characteristic features of plant evolution; although the former has likely shaped the latter, this has rarely been documented. Here we document allopolyploidy-mediated chemical defense evolution in the origin of cyanogenesis (HCN release upon tissue damage) in white clover (Trifolium repens). We combined linkage mapping of the loci that control cyanogenesis (Ac, controlling production of cyanogenic glucosides; and Li, controlling production of their hydrolyzing enzyme linamarase) with genome sequence comparisons between white clover, a recently evolved allotetraploid, and its diploid progenitors (Trifolium pallescens, Trifolium occidentale). The Ac locus (a three-gene cluster comprising the cyanogenic glucoside pathway) is derived from T.occidentale; it maps to linkage group 2O (occidentale subgenome) and is orthologous to a highly similar cluster in the T.occidentale reference genome. By contrast, Li maps to linkage group 4P (pallescens subgenome), indicating an origin in the other progenitor species. These results indicate that cyanogenesis evolved in white clover as a product of the interspecific hybridization that created the species. This allopolyploidization-derived chemical defense, together with subsequent selection on intraspecific cyanogenesis variation, appears to have contributed to white clover's ecological success as a globally distributed weed species.

Plant-Derived Pesticides as an Alternative to Pest Management and Sustainable Agricultural Production: Prospects, Applications and Challenges.

Pests and diseases are responsible for most of the losses related to agricultural crops, either in the field or in storage. Moreover, due to indiscriminate use of synthetic pesticides over the years, several issues have come along, such as pest resistance and contamination of important planet sources, such as water, air and soil. Therefore, in order to improve efficiency of crop production and reduce food crisis in a sustainable manner, while preserving consumer’s health, plant-derived pesticides may be a green alternative to synthetic ones. They are cheap, biodegradable, ecofriendly and act by several mechanisms of action in a more specific way, suggesting that they are less of a hazard to humans and the environment. Natural plant products with bioactivity toward insects include several classes of molecules, for example: terpenes, flavonoids, alkaloids, polyphenols, cyanogenic glucosides, quinones, amides, aldehydes, thiophenes, amino acids, saccharides and polyketides (which is not an exhaustive list of insecticidal substances). In general, those compounds have important ecological activities in nature, such as: antifeedant, attractant, nematicide, fungicide, repellent, insecticide, insect growth regulator and allelopathic agents, acting as a promising source for novel pest control agents or biopesticides. However, several factors appear to limit their commercialization. In this critical review, a compilation of plant-derived metabolites, along with their corresponding toxicology and mechanisms of action, will be approached, as well as the different strategies developed in order to meet the required commercial standards through more efficient methods.

Effect of Harvesting Damages on Cyanide Levels in Different Tuber Zones of Two Commonly Cultivated Cassava Varieties in <em>Mapalana</em>, Sri Lanka

Cassava is one of the staple foods consumed in developing countries. However, it contains cyanogenic glucoside which turns into toxic compound hydrogen cyanide (HCN) when damaged to the cells of cassava tubers. HCN levels of damaged and undamaged locally grown cassava varieties (MU 51 and Kirikawadi) were determined during harvesting using the titrimetric method. The results showed that the HCN level of undamaged MU 51 (14.69 ± 1.69 mgkg-1) was significantly higher (p<0.05) than that of the undamaged Kirikawadi (12.46 ± 0.58 mgkg-1) variety. The HCN level of damaged MU 51 (18.18 ± 2.83 mgkg-1) was also significantly higher (p<0.05) than the damaged Kirikawadi variety (15.07 ± 3.26 mgkg-1). Moreover, the HCN levels of both varieties were lower than the recommended safe limit of 50 mg HCN by Codex Alimentarius Commission. Further, it was found that the HCN levels of damaged tubers were significantly (p<0.05) higher than that of undamaged tubers of both varieties. The tuber cortex contained higher HCN levels followed by the parenchyma and pith. In addition, the proximal part (close to stem) of the tuber contained higher HCN levels compared to central and distal parts. However, radial HCN levels from cortex to pith showed a sharp negative gradient than the longitudinal HCN level from proximal to distal part of both cassava varieties. Further, HCN levels of damaged sites were found to be high and showed a reducing gradient from the damaged end of both varieties. Therefore, damaged cassava tubers can be consumed after removing peripheral parts at least up to 5 cm from the damaged end.

Activation and detoxification of cassava cyanogenic glucosides by the whitefly Bemisia tabaci

Two-component plant defenses such as cyanogenic glucosides are produced by many plant species, but phloem-feeding herbivores have long been thought not to activate these defenses due to their mode of feeding, which causes only minimal tissue damage. Here, however, we report that cyanogenic glycoside defenses from cassava (Manihot esculenta), a major staple crop in Africa, are activated during feeding by a pest insect, the whitefly Bemisia tabaci, and the resulting hydrogen cyanide is detoxified by conversion to beta-cyanoalanine. Additionally, B. tabaci was found to utilize two metabolic mechanisms to detoxify cyanogenic glucosides by conversion to non-activatable derivatives. First, the cyanogenic glycoside linamarin was glucosylated 1–4 times in succession in a reaction catalyzed by two B. tabaci glycoside hydrolase family 13 enzymes in vitro utilizing sucrose as a co-substrate. Second, both linamarin and the glucosylated linamarin derivatives were phosphorylated. Both phosphorylation and glucosidation of linamarin render this plant pro-toxin inert to the activating plant enzyme linamarase, and thus these metabolic transformations can be considered pre-emptive detoxification strategies to avoid cyanogenesis.

COMPARATIVE ANALYSIS OF THE PHYTOCHEMICAL CONTENT AND DESTRUCTIVE DISTILLATION OF BIOMASS CONSTITUENTS OF TWELVE TROPICAL TIMBERS IN SOUTH-EAST NIGERIA

Twelve tropical timbers indigenous to the south-east of Nigeria were analysed for their physical properties with results as follows: pH 4.26-6.72, specific gravity (0.16-0.49), charring temperature (64 -116oC) and porosity index (1.08 - 2.24%). Results of quantitative and proximate analysis of the constituent of woods studied includes; tannin (760 mg/100 g - 1240 mg/100 g), alkaloids (4.0-14.6%), flavonoids (2.0 -10.5%), saponin (2.0 - 11%), oxalate (0.28 - 2.92 g/100 g), total acidity (0.09 -0.54 g/100 cm3), cyanogenic glucoside (324-891 mg/100g), moisture content (13-31%), lipid (0.8-7.6%) and ash content (1.0-3.5%,). The qualitative screening was carried out to determine the presence of metabolites in the wood sample. Also, the destructive distillations of the timbers were studied. Results revealed their compositions as follows; wood charcoal (1.50 to 5.00 g), pyroligneous acid (2.0 -3.0 cm3), wood tar (0.1- 0.3 cm3) and wood gas (512 cm3 - 998 cm3). Thus, from the qualitative and quantitative analysis, it was observed that the timbers have medicinal properties which could be harnessed by pharmaceutical industries in drug formation or production while the products obtain from the destructive distillation of the wood can be utilized by other industries for industrial process.

Genetic divergence in transcriptional regulators of defense metabolism: insight into plant domestication and improvement.

A number of mutational changes in transcriptional regulators of defense metabolism have occurred during plant domestication and improvement. Plant domestication and improvement entail genetic changes that underlie divergence in development and metabolism, providing a tremendous model of biological evolution. Plant metabolism produces numerous specialized alkaloids, terpenoids, phenolics, and cyanogenic glucosides with indispensable roles in defense against herbivory and microbial infection. Many compounds toxic or deterrent to predators have been eliminated through domestication and breeding. Series of genes involved in defense metabolism are coordinately regulated by transcription factors that specifically recognize cis-regulatory elements in promoter regions of downstream target genes. Recent developments in DNA sequencing technologies and genomic approaches have facilitated studies of the metabolic and genetic changes in chemical defense that have occurred via human-mediated selection, many of which result from mutations in transcriptional regulators of defense metabolism. In this article, we review such examples in almond (Prunus dulcis), cucumber (Cucumis sativus), pepper (Capsicum spp.), potato (Solanum tuberosum), quinoa (Chenopodium quinoa), sorghum (Sorghum bicolor), and related species and discuss insights into the evolution and regulation of metabolic pathways for specialized defense compounds.

Badania wyciągów z liści, kwiatów, owoców i gałązek Padus avium Mill.

Introduction. The bird cherry (Padus avium Mill.) belongs to the Rosaceae family and is common in Poland. In various parts of the plant, among others, flavonoids, anthocyanins, phenolic compounds, cyanogenic glucosides, tannins, essential oil, organic acids and sugars are present. They determine astringent, anti-inflammatory, estrogenic, anesthetic, antidiabetic, cytotoxic and antibacterial properties. Aim. Determination of antioxidant activity and sum of polyphenols in leaves, flowers, fruits and young branches of bird cherry, as well as confirmation of the presence of selected flavonoids and phenolic acids. Material and methods. The research material was leaves, flowers, fruit and young twigs of Padus avium, collected from a natural site in the Noteć Forest (near Sieraków). The contents of the sum of polyphenols in the prepared extracts were determined by spectrophotometric method using the Folin-Ciocalteu (FC) reagent and the antioxidant activity by the DPPH radical method and the FRAP method, and the presence of selected flavonoids and phenolic acids was confirmed by thin-layer and paper chromatography. Results. In water and methanol extracts, the highest content of polyphenols (%) in terms of coffee acid was found in leaves (6.91 ± 0.30%; 9.02 ± 0.34%), and the lowest in fruits (2.05 ± 0, 11%; 3.11 ± 0.11%). Water and methanol extracts from leaves showed the highest antioxidant activity and the weakest water extracts from fruit (DPPH and FRAP methods). 1D-TLC, 2D-TLC and tissue paper (PC) analysis revealed the presence of rutoside in flowers and twigs, hyperoside in leaves, flowers, fruits and twigs, and most likely ferulic and vanillic acids in fruits and twigs, chlorogenic and coffee acids in all raw materials from the bird cherry. Conclusions. The highest content of polyphenolic compounds was determined in black cherry leaves, both in water and methanol extracts. The water and methanol extracts from the leaves showed the strongest antioxidant activity. The presence of rutoside, hyperoside and some phenolic acids was confirmed in the tested raw materials.

Drying kinetics and effect of drying conditions on selected physicochemical properties of foam from yellow-fleshed and white-fleshed cassava (Manihot esculenta) varieties

Fresh cassava is highly susceptible to rapid post-harvest physiological deterioration due to the high water activity. Therefore, foam mat drying was considered as an alternative drying technique for preservation. The drying kinetics of white-fleshed cassava foam (air volume fraction = 0.26, overrun = 36.0 %) and yellow-fleshed cassava foam (air volume fraction = 0.24, overrun = 32.2 %) were studied. The influence of temperature and foam thickness on moisture removal ratio (MR), drying rate, diffusivity and some important physicochemical properties of the cassava foams (CSF) during drying were researched and compared with those of non-foamed cassava pulp (NFP). The cassava foams were dried to foam powders at temperatures of 50 °C, 65 °C and 80 °C and foam thicknesses of 6 mm, 8 mm and 10 mm. The CSF exhibited two falling rates. The CSF powders had significantly lower total cyanogenic glucosides content compared to the NFP powder, and a high retention of total carotenoids. The dry foam powders had higher lightness/luminosity (L*) values than dry pulp powders. Micrographs revealed interactions between starch granules and the hydrocolloids but microstructure was not affected by increasing temperatures.

Lowered sensitivity of bitter taste receptors to β-glucosides in bamboo lemurs: an instance of parallel and adaptive functional decline in TAS2R16?

Bitter taste facilitates the detection of potentially harmful substances and is perceived via bitter taste receptors (TAS2Rs) expressed on the tongue and oral cavity in vertebrates. In primates, TAS2R16 specifically recognizes β-glucosides, which are important in cyanogenic plants' use of cyanide as a feeding deterrent. In this study, we performed cell-based functional assays for investigating the sensitivity of TAS2R16 to β-glucosides in three species of bamboo lemurs (Prolemur simus, Hapalemur aureus and H. griseus), which primarily consume high-cyanide bamboo. TAS2R16 receptors from bamboo lemurs had lower sensitivity to β-glucosides, including cyanogenic glucosides, than that of the closely related ring-tailed lemur (Lemur catta). Ancestral reconstructions of TAS2R16 for the bamboo-lemur last common ancestor (LCA) and that of the Hapalemur LCA showed an intermediate sensitivity to β-glucosides between that of the ring-tailed lemurs and bamboo lemurs. Mutagenetic analyses revealed that P. simus and H. griseus had separate species-specific substitutions that led to reduced sensitivity. These results indicate that low sensitivity to β-glucosides at the cellular level—a potentially adaptive trait for feeding on cyanogenic bamboo—evolved independently after the Prolemur–Hapalemur split in each species.

Chemical Characterization and Acceptability of Eight Cassava Varieties Introduced in Rwanda

Cassava is a staple food and an important and cheap source of carbohydrate in Rwanda. However, the nature and chemical composition of cassava roots limit its proper use as food due to its toxicity and short shelf life. The cyanogenic glucosides found in the cassava roots are responsible for the toxicity. The aim of the study was to characterize the chemical profile and consumer acceptability of paste from eight cassava varieties processed into flour using four processing methods. The cassava samples were harvested from trials conducted at Rubona Station of Rwanda Agriculture and Animal Resources Development Board. Four processing methods were used, namely, Cassava grated fermented, Cassava roots fermented, Cassava grated no fermented and Cassava roots no fermented. Pressing was done before drying the products to obtain the flour. At each stage of processing, the samples were prepared for laboratory analysis of dry mater, titratable acidity, cyanhydric acid and crude fiber by Rwanda Standards Board laboratory. Cassava flour was made into paste and sensory evaluation was conducted to evaluate the acceptability of the eight cassava varieties. The sensory attributes for the Ugali tested was significantly different (P<0.05). The method of grating before fermentation gave the most tasty Ugali than cassava root fermented. The more prefered varieties were GAHENE/2 and SEMAK 150/452 followed by BULK 13, MH95/0091 and NASE 14. The chemical analysis done for the 8 cassava varieties flour from the 4 processing methods exhibited the acceptable acidity and the NASE 14, Gahene/2 and Bulk 13 had the lowest cyanide hydrogen.

Enhancement values of cassava by-product diets on production and haemato-biochemical indices of sheep and goats: a review.

The competition for maize and soybean between humans and livestock for food has led to an increase in the cost of livestock feeds. Therefore, this has necessitated the search for alternative non-competitive feedstuffs in order to partially replace maize and soybean in small ruminant diets. The use of cassava products as a partial replacement for maize and soybean in small ruminant diet has been investigated. Cassava is a tropical crop, and its fodder is rich in crude protein (CP), minerals and vitamins with about 85% of the CP fraction exist as true protein. Cassava by-products are also high in nutrients and could contribute significantly to the nutritional needs of sheep and goats. Specifically, cassava leaves are high in CP (25.10%) with an amino acid composition similar to soybean. Evidence also exist that ruminal degradability of cassava fodder is similar to that of maize and soybean with comparable outflow rates (75%). However, the use of cassava fodder in livestock production is limited by the presence of cyanogenic glucosides (linamarin and lotaustralin) that releases hydrogen cyanide (HCN) known to cause pathophysiological changes in the liver of sheep and goats. Importantly, several processing techniques are well known to reduce or eliminate the concentrates of cyanogenic glucosides in cassava with great success. Blood chemistry and production indices of sheep and goats fed differently processed cassava by-product-based diets have been evaluated by different authors. This review revealed that cassava root sievate meal, cassava root meal and cassava peel meal are low in CP (2.29, 3.40 and 7.05%, respectively), while cassava leaf meal is high in CP (32.43%). Feed conversion efficiency of sheep and good fed cassava leaves were 9.49 and 11.24, respectively, indicating that goats utilize cassava leaves better than sheep. It is concluded that cassava by-products are low in quality protein and should be supplemented with other rich protein sources before their use in ruminant diets.