|Samac, Deborah - Debby|
|Jung, Hans Joachim|
Submitted to: Biotechnology for Fuels and Chemicals Symposium Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 5/4/2003
Publication Date: 5/4/2003
Citation: Samac, D.A., Jung, H.G., Litterer, L., Somers, D.A., Temple, G.G. 2003. Expression of UDP-glucose dehydrogenase increases accumulation of arabinose and xylose in alfalfa stems [abstract]. Biotechnology for Fuels and Chemicals Symposium Proceedings. p. 23.
Technical Abstract: In plants over 100 genes are involved in cell-wall biosynthesis. Several genes encoding enzymes in the pathways for production of the monosaccharide constituents of the cell-wall matrix have recently been cloned, paving the way for manipulating polysaccharide composition and concentration. Pectin is a complex polysaccharide consisting of galacturonic acid, galactose, arabinose, and rhamnose. With the goal of increasing the amount of pectin in alfalfa stems, we produced transgenic alfalfa plants expressing a soybean UDP-glucose dehydrogenase cDNA under the control of two promoters active in vascular tissues. In initial greenhouse experiments, enzyme activity in transgenic lines was up to 7-fold greater than in untransformed plants; however, field-grown transgenic plants had only up to 1.9-fold more activity than the control. Cell-wall polysaccharide content was lower and Klason lignin content was higher in transgenics compared to the untransformed control. No significant increase in uronic acids was observed in any line. Two neutral sugars, xylose and arabinose, which are downstream of uronic acid synthesis increased 7 to 24% in most transgenic lines compared to the control and mannose concentration decreased slightly in most lines. Increasing pectin content may require over-expression of more than one gene or redirection of glucose from cellulose synthesis.