Strategies of plant breeding for improved rumen function

Kingston‐Smith, Alison H.; Thomas, Hugh

doi:10.1111/j.1744-7348.2003.tb00224.x

Cited by 28 publications

(15 citation statements)

References 127 publications

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“…Of course, an improved retention of N inputs means decreased N outputs to the benefit of the local and wider environment. Future opportunities for improvement could arise from capitalising on the observations of species-specific differences in endogenous rates of induced proteolysis (68,83) . The results described above, together with efforts to understand the rumen interactome in terms of the microbial competition and the ecological niches required by methanogens, in addition to how their proliferation can be minimised, enable the identification of key traits required for the development of the next generation of improved forages (17) .…”

Section: Opportunities For Selective Breeding For Impact Mitigationmentioning

confidence: 99%

Plant-based strategies towards minimising ‘livestock's long shadow’

et al. 2010

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Ruminant farming is an important component of the human food chain. Ruminants can use offtake from land unsuitable for cereal crop cultivation via interaction with the diverse microbial population in their rumens. The rumen is a continuous flow fermenter for the digestion of ligno-cellulose, with microbial protein and fermentation end-products incorporated by the animal directly or during post-ruminal digestion. However, ruminal fermentation is inefficient in capturing the nutrient resource presented, resulting in environmental pollution and generation of greenhouse gases. Methane is generated as a consequence of ruminal fermentation and poor retention of ingested forage nitrogen causes nitrogenous pollution of water and land and contributes to the generation of nitrous oxide. One possible cause is the imbalanced provision of dietary substrates to the rumen micro-organisms. Deamination of amino acids by ammonia-producing bacteria liberates ammonia which can be assimilated by the rumen bacteria and used for microbial protein synthesis. However, when carbohydrate is limiting, microbial growth is slow, meaning low demand for ammonia for microbial protein synthesis and excretion of the excess. Protein utilisation can therefore be improved by increasing the availability of readily fermentable sugars in forage or by making protein unavailable for proteolysis through complexing with plant secondary products. Alternatively, realisation that grazing cattle ingest living cells has led to the discovery that plant cells undergo endogenous, stress-mediated protein degradation due to the exposure to rumen conditions. This presents the opportunity to decrease the environmental impact of livestock farming by using decreased proteolysis as a selection tool for the development of improved pasture grass varieties. Ruminant: Protein: Nitrogen: Methane: Grass: Clover: Forage Making assessments of the impact and value of livestock farming is complex. The rearing of domestic livestock is important in food production, although there are conflicts between the use of land for production of animal feed as opposed to producing grain for human consumption (1) . The livestock sector is economically valuable. Livestock contributes 1 . 4 % of global gross domestic product providing employment for 20% of the global population in both developed and developing countries (1) . Livestock products can provide an important addition to diet especially in the developing world, providing key vitamins and nutrients. Indeed, the consumption of meat has been linked to both physical and mental development in children (2) , but in the developed world over-consumption of meat has been linked to development of serious health problems (3) . Current projections estimate that the global demand for meat and milk will have doubled by 2050 compared with that at the onset of the 21st century (4) . This is being driven by demographic changes, (the emergence of a larger, but older population) and economic growth (1) . Increased demand for livestock products comes mostl...

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Section: Opportunities For Selective Breeding For Impact Mitigationmentioning

confidence: 99%

Plant-based strategies towards minimising ‘livestock's long shadow’

et al. 2010

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“…This leads to an increase of protein bypass to the ruminant's gut and improved absorption of essential amino acids, resulting in increased milk and meat production (Aerts et al, 1999;Douglas et al, 1999;McMahon et al, 2000). Moreover, decreased protein degradation in the rumen also decreases methane production and ammonium excretion in urine, which could contribute to significant reductions in emissions of the potent greenhouse gases methane and nitrous oxide from pastures (Woodward et al, 2001;Kingston-Smith and Thomas, 2003;Beauchemin et al, 2007;Smith et al, 2008). Legumes containing moderate amounts of PAs have also been associated with reduced intestinal parasite load in ruminants (Aerts et al, 1999).…”

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Expression of the R2R3-MYB Transcription Factor TaMYB14 fromTrifolium arvenseActivates Proanthocyanidin Biosynthesis in the LegumesTrifolium repensandMedicago sativa

et al. 2012

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Proanthocyanidins (PAs) are oligomeric flavonoids and one group of end products of the phenylpropanoid pathway. PAs have been reported to be beneficial for human and animal health and are particularly important in pastoral agricultural systems for improved animal production and reduced greenhouse gas emissions. However, the main forage legumes grown in these systems, such as Trifolium repens and Medicago sativa, do not contain any substantial amounts of PAs in leaves. We have identified from the foliar PA-accumulating legume Trifolium arvense an R2R3-MYB transcription factor, TaMYB14, and provide evidence that this transcription factor is involved in the regulation of PA biosynthesis in legumes. TaMYB14 expression is necessary and sufficient to up-regulate late steps of the phenylpropanoid pathway and to induce PA biosynthesis. RNA interference silencing of TaMYB14 resulted in almost complete cessation of PA biosynthesis in T. arvense, whereas Nicotiana tabacum, M. sativa, and T. repens plants constitutively expressing TaMYB14 synthesized and accumulated PAs in leaves up to 1.8% dry matter. Targeted liquid chromatography-multistage tandem mass spectrometry analysis identified foliar PAs up to degree of polymerization 6 in leaf extracts. Hence, genetically modified M. sativa and T. repens plants expressing TaMYB14 provide a viable option for improving animal health and mitigating the negative environmental impacts of pastoral animal production systems.

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“…In fact, by binding to proteins in the rumen, PAs reduce the rate of fermentation and increase the levels of proteins passing through the rumen of grazing animals. PAs therefore make the conversion of plant protein into animal protein more efficient, with reduced methane production (Kingston-Smith and Thomas, 2003). However, PAs only accumulate in the seed coats of the most valuable forage species, such as alfalfa (Medicago sativa) and clovers (Trifolium spp.…”

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Ectopic Expression of aBasic Helix-Loop-HelixGene Transactivates Parallel Pathways of Proanthocyanidin Biosynthesis. Structure, Expression Analysis, and Genetic Control ofLeucoanthocyanidin 4-ReductaseandAnthocyanidin ReductaseGenes inLotus corniculatus

et al. 2006

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Proanthocyanidins (PAs) are plant secondary metabolites and are composed primarily of catechin and epicatechin units in higher plant species. Due to the ability of PAs to bind reversibly with plant proteins to improve digestion and reduce bloat, engineering this pathway in leaves is a major goal for forage breeders. Here, we report the cloning and expression analysis of anthocyanidin reductase (ANR) and leucoanthocyanidin 4-reductase (LAR), two genes encoding enzymes committed to epicatechin and catechin biosynthesis, respectively, in Lotus corniculatus. We show the presence of two LAR gene families (LAR1 and LAR2) and that the steady-state levels of ANR and LAR1 genes correlate with the levels of PAs in leaves of wild-type and transgenic plants. Interestingly, ANR and LAR1, but not LAR2, genes produced active proteins following heterologous expression in Escherichia coli and are affected by the same basic helix-loop-helix transcription factor that promotes PA accumulation in cells of palisade and spongy mesophyll. This study provides direct evidence that the same subclass of transcription factors can mediate the expression of the structural genes of both branches of PA biosynthesis.Flavonoids represent one of the oldest, largest, and most diverse families of plant secondary metabolites. These compounds fulfill a multitude of functions during plant development (Winkel-Shirley, 2001) and are also of significant interest as antioxidant and anticancer agents in the human diet Tohge et al., 2005). Proanthocyanidins (PAs), also known as condensed tannins, are oligomeric and polymeric end products of the flavonoid biosynthetic pathway. They are widespread in nature, occurring in numerous plant species, including many important plant-derived food materials (Tanner, 2004).The beneficial effects of PAs on human health and the significant pharmacological activities of PAs have been recently reviewed (Marles et al., 2003;Dixon et al., 2005). In planta, PAs act as protectants against pathogens, pests, and diseases and additionally control seed permeability and dormancy . These compounds strongly affect plant quality traits, and the palatability and nutritive value of forage legumes are highly influenced by their concentration and structure (Barry and McNabb, 1999). High concentrations of PAs can decrease the palatability and digestibility of plants. By contrast, moderate quantities of PAs (2%-4% dry matter) in forage prevent proteolysis during ensiling and rumen fermentation, thereby protecting ruminants against pasture bloat (Tanner et al., 1995). In fact, by binding to proteins in the rumen, PAs reduce the rate of fermentation and increase the levels of proteins passing through the rumen of grazing animals. PAs therefore make the conversion of plant protein into animal protein more efficient, with reduced methane production (Kingston-Smith and Thomas, 2003). However, PAs only accumulate in the seed coats of the most valuable forage species, such as alfalfa (Medicago sativa) and clovers (Trifolium spp.), and are absent fro...

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Strategies of plant breeding for improved rumen function

Cited by 28 publications

References 127 publications

Plant-based strategies towards minimising ‘livestock's long shadow’

Plant-based strategies towards minimising ‘livestock's long shadow’

Expression of the R2R3-MYB Transcription Factor TaMYB14 fromTrifolium arvenseActivates Proanthocyanidin Biosynthesis in the LegumesTrifolium repensandMedicago sativa

Ectopic Expression of aBasic Helix-Loop-HelixGene Transactivates Parallel Pathways of Proanthocyanidin Biosynthesis. Structure, Expression Analysis, and Genetic Control ofLeucoanthocyanidin 4-ReductaseandAnthocyanidin ReductaseGenes inLotus corniculatus

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