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Title: Expression analysis of Medicago stem internodes identifies genes associated with regulatory control and biogenesis of plant cell walls

item Jung, Hans Joachim
item Samac, Deborah - Debby
item Gronwald, John
item Lamb, Joann
item Vance, Carroll

Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 4/4/2008
Publication Date: 6/22/2008
Citation: Tesfaye, M., Jung, H.G., Samac, D.A., Gronwald, J.W., Lamb, J.F., Vance, C.P., Vandenbosch, K.A. 2008. Expression analysis of Medicago stem internodes identifies genes associated with regulatory control and biogenesis of plant cell walls [abstract]. American Society of Plant Biologists Annual Meeting, Pan American Congress on Plants and BioEnergy, June 22-25, 2008, Merida, Mexico. Abstract No. P02014. Available:

Interpretive Summary:

Technical Abstract: Legumes have many traits that make them attractive bioenergy crops, especially as components of mixed grass stands or in crop rotations with maize. Alfalfa (Medicago sativa) is a legume with an advantage as a biomass crop because of its ability to fix atmospheric nitrogen and the easy separation of co-products: leaf meal for livestock and stems for conversion to syngas and/or fermentation to ethanol. Nevertheless, studying alfalfa is challenging because it is a cross-pollinated autotetraploid, with complex segregation and inheritance patterns. Evaluation of the closely related diploid barrel medic (Medicago truncatula), with well-developed genetic and genomic resources, would facilitate analysis of biomass traits. We expect that understanding of systems controlling primary and secondary cell wall composition in Medicago will facilitate improvement of biomass production (e.g., cellulose quantity) or quality (e.g., reduced lignin) in alfalfa and related dicots. Stems of alfalfa and M. truncatula undergo two distinct developmental phases: primary growth in elongating stem internodes, involving increase in cell size and deposition of primarily non-lignified primary cell walls, and cambial activity in post-elongation internodes, resulting in deposition of secondary xylem (containing secondary walls rich in lignin and cellulose). We have utilized the Affymetrix Medicago genome array, which contains >50,000 probe sets, to profile expression patterns in stems of two M. truncatula ecotypes and two alfalfa clones with contrasting cell wall composition. Transcripts were detected from 33% to 47% of probe sets, depending on genotype. Most of the detected genes were expressed in both elongating and post-elongation stems, although at different expression levels. Numerous genes with differential expression patterns have predicted roles in cell wall biosynthesis, structure and modification, transcriptional regulation, and signaling. Our poster will explore patterns of cell wall-related gene expression in stems and discuss the potential for exploiting natural variation among genotypes to identify genes regulating cell wall traits.