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

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Type Article
Original languageEnglish
Pages (from-to)264-280
Number of pages17
JournalPlant Biotechnology Journal
Volume6
Issue number3
Early online date18 Dec 2007
DOI
Publication statusPublished - Apr 2008
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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-β-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.

Keywords

  • cell wall, digestibility, ferulic acid esterase, forage grass, hydroxycinnamic acids, transgenic plant