Abstract
BackgroundThe development of transgenic plants as a production platform for biomass-degrading enzymes is a promising tool for an economically feasible allocation of enzymes processing lignocellulose. Previous research has already identified a major limitation of in planta production such as interference with the structure and integrity of the plant cell wall resulting in a negative influence on plant growth and development.ResultsHere, we describe the in planta expression of endoglucanase TrCel5A from the mesophilic fungus Trichoderma reesei with differential intracellular targeting and evaluate its impact on the tobacco cell wall composition. Targeting of the enzyme to the apoplast leads to distinct changes in cell polysaccharides such as glucose level in the matrix polysaccharides (MPS). These effects are combined with severe changes in plant development. Retention of TrCel5A in the endoplasmic reticulum (ER) could avoid visible effects on plant growth under the chosen conditions, but exhibits changes in the composition of the MPS.ConclusionsThese results give new insights into the complex interaction of heterologous cellulase expression with cell wall development and it outlines novel promising strategies to engineer plant cell walls for improved biomass processing.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-015-0443-3) contains supplementary material, which is available to authorized users.
Highlights
The development of transgenic plants as a production platform for biomass-degrading enzymes is a promising tool for an economically feasible allocation of enzymes processing lignocellulose
For plants retaining TrCel5A inside the endoplasmic reticulum (ER), the endoglucanase gene was fused to the sequence for a C-terminal KDEL signal (Additional file 1 Supplemental figures)
Constructs encoding the enzyme with and without the KDEL tag were introduced into tobacco (Nicotiana tabacum SR1) leaf discs by Agrobacterium-mediated transformation [36]
Summary
The development of transgenic plants as a production platform for biomass-degrading enzymes is a promising tool for an economically feasible allocation of enzymes processing lignocellulose. Structural polysaccharides, as part of the lignocellulose and the plant cell wall, represent an extensive source of fermentable carbohydrates [3]. These polysaccharides, consisting of cellulose, hemicellulose and pectin, form a highly cross linked network providing the cell shape tensile properties and the structural stability of the plant [4]. These characteristics are responsible for a major drawback in enzymatic lignocellulose utilization. Without additional pretreatment the conversion of plant cell walls to fermentable sugar is comparatively slow
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