Submitted to: International Conference on Legume Genomics and Genetics
Publication Type: Abstract Only
Publication Acceptance Date: 6/7/2004
Publication Date: 6/7/2004
Citation: Samac, D.A., Dornbusch, M.R. 2004. Gene expression in developing seed coats of Medicago sativa [abstract]. Second International Conference on Legume Genomics and Genetics, June 7-11, 2004, Dijon, France. p. 266.
Technical Abstract: The parenchyma cells of seed coats and procumbent trichomes on leaves and stems are the only cells reported to contain proanthocyanidins (PAs; condensed tannins) in alfalfa (lucerne; Medicago sativa). In seed coats, PAs function in defense against insects and pathogens and in maintenance of seed dormancy. They may also have antinutritional properties in humans and monogastric animals by retarding protein digestion and micronutrient absorption. Expression of PAs in the foliage of alfalfa is desired to reduce the occurrence of pasture bloat, a potentially lethal foaming of digesta in the rumen from rapid breakdown of fresh alfalfa. The transparent testa and other Arabidopsis seed color mutants have greatly accelerated the cloning of genes in the PA biosynthetic pathway and understanding spatiotemporal regulation of flavonoid production. To better understand the regulation of PA biosynthetic genes in alfalfa, expression of genes involved in PA biosynthesis is being compared over time (2-34 days post-pollination) in developing seeds from alfalfa plants with wildtype tan-colored seed coats and dark brown-colored seed coats (UMN2163). The presence of PAs was visualized by staining with 4-dimethylaminocinnamaldehyde (DMACA). PAs were observed in seed coats of both genotypes at the first time point, 10 days post-pollination, in cells surrounding the hilum. By 14 days post-pollination, staining was observed over the entire surface of the seed. Staining was limited to the pallisade layer of cells of the seed coat. Red coloration of the seed coats of UMN2163 was observed from 10 to 34 days-post pollination. This line has similarity with the banyuls (ban) mutant of Arabidopsis in which anthocyanidin reductase is inactive, leading to increased anthocyanin accumulation in the seed coat. A nylon filter macroarray has been developed using cDNAs from Medicago truncatula. Included on the macroarray are 32 cDNAs for enzymes in the flavonoid biosynthetic pathway, including enzymes involved in isoflavonoid, lignin, anthocyanin, and PA biosynthesis, 14 cDNAs with sequence similarity to myb-like and myc-like transcription regulators, and 8 cDNAs of seed storage protein genes. Results of macroarray hybridizations using probes from young developing seeds of wildtype and UMN2163 alfalfa will be presented. This research may have implications for obtaining PA synthesis in alfalfa leaf mesophyll cells for management of pasture bloat.