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.

SWAPDT: A method for Short-time Withering Assessment of Probability for Drought Tolerance in Camellia sinensis validated by targeted metabolomics

“…Coumaric acid levels were lower in DT than in DS cultivars. This correlates with the results obtained in a study by Hu et al (1999) where coumaric acid levels significantly increased in the xylem sap of DS maize plants over a 12 day period. Coumaric acid was identified as an intermediate in lignin biosynthesis in water stressed maize, which explains an increase in coumaric acid (Hu et al, 1999) to prevent water loss.…”

BUD2, encoding an S-adenosylmethionine decarboxylase, is required for Arabidopsis growth and development

“…To observe the vascular patterns of Arabidopsis inflorescences and roots, the fresh hand-cut sections or microtome-sliced sections were observed directly under the UV light at 340-380 nm [41]. For histochemical localization of lignin, freshly hand-cut sections (~20 µm thick) of inflorescences or roots were incubated for 2 min in 2% phloroglucine solution (Sigma, USA), mounted in 50% HCl [42] and photographed with a Micro Color CCD camera (Apogee Instruments INC, USA).…”

Gene silencing: concepts, applications, and perspectives in woody plants

“…In the transgenic lines obtained plant growth was substantially enhanced, and structural integrity maintained both at the cellular and whole-plant levels (Hu et al, 1999).…”

“…The production of plant material with lower contents of lignin would mean a significant reduction of cost and pollution to the paper industry. One of the approaches to obtain reduced lignin forest trees has been the down regulation of lignin biosynthesis pathways (Hu et al, 1999). The main genes involved with genetic transformation targeting lignin reduction are 4-coumarate: coenzyme A ligase (Pt4CL1) (Hu et al, 1999), cynnamyl alcohol deshydrogenase (CAD -the final enzyme in the biosynthesis of lignin monomers) (Baucher et al, 1996) and caffeate/5-hydroxyferulate O-methyltransferase (COMT -enzyme involved in syringyl lignin synthesis) (Lapierre et al, 1999).…”