Downregulation of Caffeic Acid 3-<i>O</i>-Methyltransferase and Caffeoyl CoA 3-<i>O</i>-Methyltransferase in Transgenic Alfalfa: Impacts on Lignin Structure and Implications for the Biosynthesis of G and S Lignin

Guo, Dianjing; Chen, Fang; Inoue, Kentaro; Blount, Jack W.; Dixon, Richard A.

doi:10.1105/tpc.13.1.73

Cited by 436 publications

(290 citation statements)

References 53 publications

(73 reference statements)

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“…Reddy et al (2005) reported a strong negative linear relationship between in situ digestibility and ADL levels across all reduced lignin lines. In addition to increased digestibility, reduced lignin alfalfa populations have also shown reduced NDF concentrations and greater non-fiber carbohydrate concentrations compared to control lines (Guo et al, 2001b;Reddy et al, 2005;Getachew et al, 2011;Li et al, 2015a), while CP concentrations remained similar for reduced lignin and reference alfalfa lines (Getachew et al, 2011;Li et al, 2015a).…”

Section: Introductionmentioning

confidence: 94%

“…Populations of reduced lignin alfalfa have shown an increase in in vitro DMD, in situ rumen digestibility, and in vitro NDFD (Guo et al, 2001b;Reddy et al, 2005;Mertens and McCaslin, 2008;Weakley et al, 2008;Undersander et al, 2009;Getachew et al, 2011). Reddy et al (2005) reported a strong negative linear relationship between in situ digestibility and ADL levels across all reduced lignin lines.…”

Section: Introductionmentioning

confidence: 97%

“…Several experimental lines of alfalfa have been developed with downregulation of the caffeic acid 3-O-methyltransferase (COMT) and caffeoyl CoA 3-O-methyltransferase (CCOMT) lignin biosynthetic genes (Inoue et al, 1998;Guo et al, 2001a;Marita et al, 2003;Getachew et al, 2011). Experimental populations of COMT and/or CCOMT downregulated alfalfa have shown a 4 to 29% decrease in stem lignin concentration and a 1 to 24% decrease in herbage lignin concentration compared to reference alfalfa cultivars (Guo et al, 2001a;2001b;Marita et al, 2003;Reddy et al, 2005;Undersander et al, 2009;Getachew et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

“…Experimental populations of COMT and/or CCOMT downregulated alfalfa have shown a 4 to 29% decrease in stem lignin concentration and a 1 to 24% decrease in herbage lignin concentration compared to reference alfalfa cultivars (Guo et al, 2001a;2001b;Marita et al, 2003;Reddy et al, 2005;Undersander et al, 2009;Getachew et al, 2011). The wide variation in lignin reduction reported could be due to the specific downregulated gene (Guo et al, 2001a(Guo et al, , 2001bMarita et al, 2003;Undersander et al, 2009;Getachew et al, 2011), the methods used for lignin analysis (Guo et al, 2001a;2001b;Jung et al, 2012), or the plant growing conditions (Baucher et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

“…Recently released reduced lignin alfalfa cultivars have potential to increase the digestibility of alfalfa forage compared to reference cultivars (Guo et al, 2001a(Guo et al, , 2001bMarita et al, 2003;Reddy et al, 2005;Getachew et al, 2011). These improvements in alfalfa forage nutritive value may lengthen the time period when alfalfa has a forage nutritive value suitable for high-producing livestock.…”

Section: Introductionmentioning

confidence: 99%

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Forage Accumulation and Nutritive Value of Reduced Lignin and Reference Alfalfa Cultivars

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Core Ideas Reduced lignin and reference cultivars did not differ in forage accumulation. Forage accumulation was greater with a fall harvest or a 40‐d cutting schedule. Reduced lignin alfalfa averaged 8% less acid detergent lignin and 10% greater neutral detergent fiber digestibility. Cutting treatments with shorter harvest intervals increased forage nutritive value. Delaying reduced lignin alfalfa harvest increased forage mass and maintained quality. Reduced lignin alfalfa (Medicago sativa L.) cultivars have the potential to increase the feeding value of alfalfa for livestock by improving forage fiber digestibility and to increase harvest management flexibility. The objectives were to compare the forage accumulation and nutritive value of reduced lignin and reference alfalfa cultivars when subject to diverse cutting treatments in the establishment and first production year. Research was established in 2015 at four locations in Minnesota. Reference alfalfa cultivars 54R02, DKA43–22RR, WL 355.RR, and the reduced lignin cultivar 54HVX41 were subject to cutting treatments with variable intervals between harvests. Cultivar by cutting treatment interactions were not significant (P > 0.05), but cultivar and cutting treatment effects were significant. Cultivars did not consistently differ in forage accumulation. Establishment year forage accumulation was greater when a fall harvest was taken, and first production year forage accumulation was generally greatest when alfalfa was harvested on a 40‐d cutting schedule. Compared to reference alfalfa cultivars, 54HVX41 had an average of 8% less acid detergent lignin (ADL) and 10% greater neutral detergent fiber digestibility (NDFD) but was similar in crude protein (CP) and neutral detergent fiber (NDF) concentrations. Cutting treatments with shorter harvest intervals increased forage CP and NDFD and decreased NDF and ADL concentrations. With a 5‐d harvest delay, 54HVX41 harvested on a 35‐d harvest interval had a 21% gain in forage mass and a 3% reduction in relative forage quality (RFQ) compared to reference cultivars harvested on a 30‐d harvest interval, which could allow for increased management flexibility.

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Section: Introductionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Forage Accumulation and Nutritive Value of Reduced Lignin and Reference Alfalfa Cultivars

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Forestry

Cooke¹,

Morse²,

Davis³

2004

Handbook of Plant Biotechnology

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Genetic improvement plays a pivotal role in intensive management strategies for forest trees. Conventional breeding in forest trees is greatly constrained by long generation times. This is particularly true for temperate coniferous species, which rank among the most commercially important forest trees. In Aadditionally, many traits of interest exhibit poor correlation between the juvenile and mature phases of growth that are innate to trees. Consequently, these traits cannot be reliably evaluated at the morphological level until the tree has entered into mature growth, which may take several years. Given these constraints to conventional breeding, the use of biotechnology to reduce the time to create and select genetically improved trees could have a significant impact on forest tree improvement and the forest industry. In this chapter, we focus on how biotechnology has been and can be incorporated into forestry.

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Monolignol Biosynthesis and its Genetic Manipulation: The Good, the Bad, and the Ugly

Dixon

Reddy

Gallego‐Giraldo³

2014

Recent Advances in Polyphenol Research

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Economic and environmental factors favor the adoption of lignocellulosic bioenergy crops for production of liquid transportation fuels. However, lignocellulosic biomass is recalcitrant to saccharification (sugar release from cell walls), and this is, at least in part, due to the presence of the phenylpropanoid-derived cell wall polymer lignin. A large body of evidence exists documenting the impacts of lignin modification in plants. This technology can lead to improved forage quality and enhanced processing properties for trees (paper pulping) and lignocellulosic energy crops. We here provide a comprehensive review of the literature on lignin modification in plants. The pathway has been targeted through down-regulating expression of the enzymes of the monolignol pathway, as well as through down-regulation or over-expression of transcription factors that control lignin biosynthesis and/or programs of secondary cell wall development. Targeting lignin modification at some steps in the monolignol pathway can result in impairment of plant growth and development, often associated with the triggering of endogenous host defense mechanisms. Recent studies suggest that it may be possible to decouple negative growth impacts from lignin reduction.Keywords: monolignol biosynthesis, genetic modification, transcription factor, gene silencing, saccharification. 2 IntroductionLignin is a major component of plant secondary cell walls, and the second most abundant plant polymer on the planet. Lignin constitutes about 15-35% of the dry mass of vascular plants (Adler, 1977). Considerable attention has been given over the past several years to the reduction of lignin content in model plant species, forages, trees, and dedicated bioenergy feedstocks. This is because forage digestibility, paper pulping and liquid fuel production from biomass through fermentation are all affected by recalcitrance of lignocellulose, primarily due to the presence of lignin, which blocks accessibility of the sugar-rich cell wall polysaccharides cellulose and hemicellulose to enzymes and microorganisms (Pilate et al., 2002;Reddy et al., 2005;.Much is now known of the biosynthesis of lignin and its control at the transcriptional level. This information informs the targets that have been selected for genetic modification of lignin content and composition in transgenic plants. There is considerable variation in the effects on lignin content and composition depending on the gene that is targeted for down-or up-regulation. Equally important, lignin modification can have profound impacts on plant growth and development, ranging from good through bad to "downright ugly", but these impacts are again strongly target dependent. Understanding the mechanisms that may impact plant growth, which equate to agronomic performance, in crop species "improved" through lignin modification is critical for economic advancement of the forage and biofuels industries. Although still poorly understood, these mechanisms may also throw light on basal plant developmental and de...

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Downregulation of Caffeic Acid 3-O-Methyltransferase and Caffeoyl CoA 3-O-Methyltransferase in Transgenic Alfalfa: Impacts on Lignin Structure and Implications for the Biosynthesis of G and S Lignin

Cited by 436 publications

References 53 publications

Forage Accumulation and Nutritive Value of Reduced Lignin and Reference Alfalfa Cultivars

Forage Accumulation and Nutritive Value of Reduced Lignin and Reference Alfalfa Cultivars

Forestry

Monolignol Biosynthesis and its Genetic Manipulation: The Good, the Bad, and the Ugly

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