Marcia M. de O. Buanafina

Bio: Marcia M. de O. Buanafina is an academic researcher from Pennsylvania State University. The author has contributed to research in topics: Cell wall & Ferulic acid. The author has an hindex of 9, co-authored 15 publications receiving 391 citations. Previous affiliations of Marcia M. de O. Buanafina include Aberystwyth University.

Expression of a fungal ferulic acid esterase increases cell wall digestibility of tall fescue (Festuca arundinacea)

Abstract: In the cell walls of forage grasses, ferulic acid is esterified to arabinoxylans and participates with lignin monomers in oxidative coupling pathways to generate ferulate-polysaccharide-lignin complexes that cross-link the cell wall. Such cross-links hinder cell wall degradation by ruminant microbes, reducing plant digestibility. In this study, genetically modified Festuca arundinacea plants were produced expressing an Aspergillus niger ferulic acid esterase (FAEA) targeted to the vacuole. The rice actin promoter proved to be effective for FAEA expression, as did the cauliflower mosaic virus (CaMV) 35S and maize ubiquitin promoters. Higher levels of expression were, however, found with inducible heat-shock and senescence promoters. Following cell death and subsequent incubation, vacuole-targeted FAEA resulted in the release of both monomeric and dimeric ferulic acids from the cell walls, and this was enhanced several fold by the addition of exogenous endo-1,4-beta-xylanase. Most of the FAEA-expressing plants showed increased digestibility and reduced levels of cell wall esterified phenolics relative to non-transformed plants. It is concluded that targeted FAEA expression is an effective strategy for improving wall digestibility in Festuca and, potentially, other grass species used for fodder or cellulosic ethanol production.

Targeting expression of a fungal ferulic acid esterase to the apoplast, endoplasmic reticulum or golgi can disrupt feruloylation of the growing cell wall and increase the biodegradability of tall fescue (Festuca arundinacea).

Abstract: In the cell walls of grasses, ferulic acid is esterified to arabinoxylans and undergoes oxidative reactions to form ferulates dimers, trimers and oligomers. Feruloylation of arabinoxylan is considered important not only because it leads to cross-linked xylans but also because ferulates may act as a nucleating site for the formation of lignin and hence link arabinoxylans to lignin by forming a lignin-ferulate-arabinoxylan complex. Such cross-linking is among the main factors inhibiting the release of fermentable carbohydrates from grasses either for ruminant nutrition or for biofuel production. We have found that significant reductions in the levels of monomeric and dimeric phenolics can be achieved in the growing cell walls during plant development in leaves of Festuca arundinacea by constitutive intracellular targeted expression of Aspergillus niger ferulic acid esterase (FAEA). We propose that this occurred by directly disrupting ester bonds linking phenolics to cell wall polysaccharides by apoplast targeting or by preventing excessive feruloylation of cell wall carbohydrates prior to their incorporation into the cell wall, by targeting to the Golgi membrane system. Plants with lower cell wall ferulate levels, which showed increased digestibility and increased rates of cellulase-mediated release of fermentable sugars, were identified. Targeting FAE to the Golgi was found to be more effective than targeting to the ER, which supports the current theories of the Golgi as the site of feruloylation of arabinoxylans. It is concluded that targeting FAEA expression to the Golgi or apoplast is likely to be an effective strategy for improving wall digestibility in grass species used for fodder or cellulosic ethanol production.

Manipulating the phenolic acid content and digestibility of Italian ryegrass (Lolium multiflorum) by vacuolar targeted expression of a fungal ferulic acid esterase

Abstract: In grass cell walls, ferulic acid esters linked to arabinosyl residues in arabinoxylans play a key role in crosslinking hemicellulose Although such crosslinks have a number of important roles in the cell wall, they also hinder the rate and extent of cell wall degradation by ruminant microbes and by fungal glycohydrolyase enzymes Ferulic acid esterase (FAE) can release both monomeric and dimeric ferulic acids from arabinoxylans making the cell wall more susceptible to further enzymatic attack Transgenic plants of Lolium multiflorum expressing a ferulic acid esterase gene from Aspergillus niger, targeted to the vacuole under a constitutive rice actin promoter, have been produced following microprojectile bombardment of embryogenic cell cultures The level of FAE activity was found to vary with leaf age and was highest in young leaves FAE expression resulted in the release of monomeric and dimeric ferulic acids from cell walls on cell death and this was enhanced severalfold by the addition of exogenous beta-1,4-endoxylanase We also show that a number of plants expressing FAE had reduced levels of cell wall esterified monomeric and dimeric ferulates and increased in vitro dry-matter digestibility compared with nontransformed plants

Functional testing of a PF02458 homologue of putative rice arabinoxylan feruloyl transferase genes in Brachypodium distachyon.

Abstract: We show that changing the expression of a putative feruloyl transferase gene belonging to the BAHD acyl-transferase family alters the levels of cell wall esterified ferulates and diferulates in Brachypodium distachyon cell walls. While the potential of grass cell walls for biofuel production has been realized, the technology for lignocellulosic biomass conversion for the production of ethanol is still inefficient because of structural mechanisms that plants have evolved to make the cell wall recalcitrant to enzymatic attack. One of these mechanisms in grasses involves the esterification of arabinoxylans in the cell wall with ferulic acid via an ester linkage to arabinose side chains on xylans. These ferulates undergo oxidative coupling reactions to form ferulate dimers, thus crosslinking polysaccharides. Arabinoxylan feruloylation is an important factor that determines cell wall recalcitrance because it directly cross-links xylans and because ferulates act as nucleating sites for the formation of lignin and for the linkage of lignin to the xylan/cellulose network. Here we report on the effects of changing the expression of Bradi2g43520 (BdAT1), a homologue of the rice feruloyl transferase gene Os01g42880 belonging to the Pfam PF02458 family, in Brachypodium distachyon. Down regulation in several independent RNAi::BdAT1 lines, resulted in up to a 35 % reduction of ferulate levels in both leaves and stems compared to control plants, over 2-3 generations of selfing. In contrast, overexpression of putative BdAT1 resulted in an increase of up to 58 and 47 % of ferulate levels in leaves and stems, respectively, compared to control plants and analyzed over 2-3 generations of selfing. These findings suggest that Bradi2g43520 may be a good candidate for feruloylation of AX in Brachypodium.

Biotechnology on genetic control of lignin biosynthesis in trees -Repression of lignin biosynthesis promotes cellulose accumulation and growth in transgenic trees-

Abstract: Because lignin limits the use of wood for fiber, chemical, and energy production, strategies for its downregulation are of considerable interest. We have produced transgenic aspen (Populus tremuloides Michx.) trees in which expression of a lignin biosynthetic pathway gene Pt4CL1 encoding 4-coumarate:coenzyme A ligase (4CL) has been downregulated by antisense inhibition. Trees with suppressed Pt4CL1 expression exhibited up to a 45% reduction of lignin, but this was compensated for by a 15% increase in cellulose. As a result, the total lignin–cellulose mass remained essentially unchanged. Leaf, root, and stem growth were substantially enhanced, and structural integrity was maintained both at the cellular and whole-plant levels in the transgenic lines. Our results indicate that lignin and cellulose deposition could be regulated in a compensatory fashion, which may contribute to metabolic flexibility and a growth advantage to sustain the long-term structural integrity of woody perennials.

The Cell Wall

Abstract: Secondary thickening in pteridophytes.-The known cases of secondary thickening in recent Pteridophyta have been brought together by HILL23 in a useful resume. After stating the criteria for secondary growth, Botrychium, which has a distinct cambium, and Ophioglossum, which lacks a definite layer, are described, followed by Angiopteris and Marattia, in which a cambium forms a few xylem elements. CORMACK'S observations on the secondary wood in the nodes of Equisetum are cited, though no reference is made to the cambium in the young cone as reported by J]FFREY.24 The other cases of secondary growth include Psilotum, Selaginella spinulosa, and several species of Isoetes, especially I. hystrix, which may show a cambium outside the vascular cylinder.-M. A.

Biochemistry And Molecular Biology Of Plants

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Room Temperature Ionic Liquids as Emerging Solvents for the Pretreatment of Lignocellulosic Biomass

Abstract: Room temperature ionic liquids (RTILs) are emerging as attractive and green solvents for lignocellulosic biomass pretreatment. The unique solvating properties of RTILs foster the disruption of the 3D network structure of lignin, cellulose, and hemicellulose, which allows high yields of fermentable sugars to be produced in subsequent enzymatic hydrolysis. In the current review, we summarize the physicochemical properties of RTILs that make them effective solvents for lignocellulose pretreatment including mechanisms of interaction between lignocellulosic biomass subcomponents and RTILs. We also highlight several recent strategies that exploit RTILs and generate high yields of fermentable sugars suitable for downstream biofuel production, and address new opportunities for use of lignocellulosic components, including lignin. Finally, we address some of the challenges that remain before large-scale use of RTILs may be achieved.