Flavonoids, natural products abundant in the model legume Glycine max, confer benefits to plants and to animal health. Flavonoids are present in soybean mainly as glycoconjugates. However, the mechanisms of biosynthesis of flavonoid glycosides are largely unknown in G. max. In the present study, 212 putative UDP-glycosyltransferase (UGT) genes were identified in G. max by genome-wide searching. The GmUGT genes were distributed differentially among the 20 chromosomes, and they were expressed in various tissues with distinct expression profiles. We further analyzed the enzymatic activities of 11 GmUGTs that are potentially involved in flavonoid glycosylation, and found that six of them (UGT72X4, UGT72Z3, UGT73C20, UGT88A13, UGT88E19 and UGT92G4) exhibited activity toward flavonol, isoflavone, flavone and flavanol aglycones with different kinetic properties. Among them, UGT72X4, UGT72Z3 and UGT92G4 are flavonol-specific UGTs, and UGT73C20 and UGT88E19 exhibited activity toward both flavonol and isoflavone aglycones. In particular, UGT88A13 exhibited activity toward epicatechin, but not for the flavonol aglycones kaempferol and quercetin. Overexpression of these six GmUGT genes significantly increased the contents of isoflavone and flavonol glucosides in soybean hairy roots. In addition, overexpression of these six GmUGT genes also affected flavonol glycoside contents differently in seedlings and seeds of transgenic Arabidopsis thaliana. We provide valuable information on the identification of all UGT genes in soybean, and candidate GmUGT genes for potential metabolic engineering of flavonoid compounds in both Escherichia coli and plants.

Alfalfa (Medicago sativa L.) is an important legume forage crop with great economic value. However, as the growth of alfalfa is seriously affected by an inadequate supply of water, drought is probably the major abiotic environmental factor that most severely affects alfalfa production worldwide. In an effort to enhance alfalfa drought tolerance, we transformed the Arabidopsis Enhanced Drought Tolerance 1 (AtEDT1) gene into alfalfa via Agrobacterium-mediated transformation. Compared with wild type plants, drought stress treatment resulted in higher survival rates and biomass, but reduced water loss rates in the transgenic plants. Furthermore, transgenic alfalfa plants had increased stomatal size, but reduced stomatal density, and these stomatal changes contributed greatly to reduced water loss from leaves. Importantly, transgenic alfalfa plants exhibited larger root systems with larger root lengths, root weight, and root diameters than wild type plants. The transgenic alfalfa plants had reduced membrane permeability and malondialdehyde content, but higher soluble sugar and proline content, higher superoxide dismutase activity, higher chlorophyll content, enhanced expression of drought-responsive genes, as compared with wild type plants. Notably, transgenic alfalfa plants grew better in a 2-year field trial and showed enhanced growth performance with increased biomass yield. All of our morphological, physiological, and molecular analyses demonstrated that the ectopic expression of AtEDT1 improved growth and enhanced drought tolerance in alfalfa. Our study provides alfalfa germplasm for use in forage improvement programs, and may help to increase alfalfa production in arid lands.