Birgitte Skadhauge

LEUCOCYANIDIN REDUCTASE ACTIVITY AND ACCUMULATION OF PROANTHOCYANIDINS IN DEVELOPING LEGUME TISSUES

Proanthocyanidin (PA) and anthocyanin accumulation and location in developing leaves, flowers, and seeds of the legumes Medicago sativa, Lotus japonicus, Lotus uliginosus, Hedysarum sulfurescens, and Robinia pseudacacia were investigated by quantitative measurements and by histological analysis after staining with 1% vanillin/HCl, butanol/HCl, or 50% HC1. M. sativa leaves and flowers, L. japonicus leaves, and R. pseudacacia flowers do not contain PAs, but seeds of all investigated species contain PAs. Anthocyanins are absent in the seed coats of all five species and in leaves of L. japonicus. PA content generally increases as a function of development in leaves, but declines in flowers. With the exception of H. sulfurescens, flower PAs are synthesized in the parenchyma cells of the standard petal, while anthocyanins are located in the neighboring epidermal cells. Leucocyanidin reductase (LCR) catalyzes the conversion of 2,3-trans-3,4-cis-leucocyanidin to (+)-catechin and is the first enzyme in the PA-specific pathway. LCR activity was only detected in PA-containing tissues and generally declined during tissue development.

Effects of proanthocyanidins, dehulling and removal of pericarp on digestion of barley grain by ruminal micro-organisms

The effects of proanthocyanidins (PA), dehulling, and removal of the pericarp on the rate and extent of barley digestion by ruminal micro-organisms were studied using a control barley (cv Harrington) and three PA-free barley lines (Caminant, Ca5043l6 and Ca802711). Each barley was studied in five preparations: whole grain (W); dehulled kernels (DH); kernels with pericarp removed (DP); dry-rolled grain (DR), and the pericarp-testa fraction (PT) produced during preparation of DP. Vanillin-HCl staining and chemical analysis confirmed that PA were present only in the Harrington barley, and localised in the pericarp-testa layer. Whole kernels, DH and DP were incubated with diluted ruminal fluid in vitro, and all five preparations were incubated in situ (nylon bag technique). Harrington DR and all four PT fractions were also incubated in vitro in the presence (0.074% w/v) and absence of polyethylene glycol (PEG), which specifically binds PA. The four barleys did not differ in in vitro dry matter disappearance (DMD) or gas production from W, DH or DP preparations, nor in in situ DMD rates from W, DH or DP (P > 0.05). In vitro DMD and gas production among PT fractions from the four barleys were also similar (P > 0.05), as were in vitro DMD from PEG-present and PEG-absent DR Harrington. With Harrington PT, in vitro ammonia concentrations were higher (P < 0.05) with PEG than without. For each barley line, in vitro DMD rates were highest (P < 0.01) with DP, followed by DH, and then by W (P < 0.01). In in situ incubations also, DMD rates and effective degradabilities of DR samples exceeded (P < 0.05) those of DH samples. It was concluded that the presence of proanthocyanidins did not affect ruminal digestion of barley grain, and that abrasive milling to breach the hull and pericarp may be a promising method by which to regulate the rate of barley digestion in the rumen.

Variation in morphology, plant habit, proanthocyanidins, and flavonoids within a Lottus germplasm collection

Lotus species collec ted from a range of geographical locations were evaluated for relationships between plant habit and size, leaf proanthocyanidin (PA) content, flower colour, stem colour, leaf colour, trichome density, and geographic origin. No relationships occurred between leaf PA concentration and morphological trait or collection site. Trichome coverage was moderately correlated with plant size (r = -0.70). Several accessions, e.g., L. angustissimus L. and L. castellanis Boiss. & Reut., consisted of small, trichome-covered plants distinct from the large, glabrous plants typical of the model species L. corniculatus var. japonicus ecotype Gifu B129. These two morphology types were also represented among the tan mutants of Gifu B129. Due to the importance of trichomes and PA in plant defence, PA composition was compared between L. angustissimusand tan1 (both representing the small trichome-covered phenotype) and ecotype Gifu B129 and tan2 (both representing the large, glabrous phenotype). Both the tan...

Genetic Systems for Condensed Tannin Biotechnology

Condensed tannins (proanthocyanidins) are plant phenolic polymers with protein-binding, carbohydrate-binding, and antioxidant properties. Dietary condensed tannins deter some insects from feeding on crops, disrupt insect digestion and growth,1 and deter larger browsing and foraging animals.2 As well, the very high levels of condensed tannins found in tropical plant species likely protect these plants from the damaging effects of strong sunlight. Patterns of expression of condensed tannins vary widely within tissues and among plant species, but could be substantially improved in some plant species to suit agricultural and industrial applications.

Mutations in the gene of the Gα subunit of the heterotrimeric G protein are the cause for the brachytic1 semi-dwarf phenotype in barley and applicable for practical breeding

BackgroundShort-culm mutants have been widely used in breeding programs to increase lodging resistance. In barley (Hordeum vulgare L.), several hundreds of short-culm mutants have been isolated over the years. The objective of the present study was to identify the Brachytic1 (Brh1) semi-dwarfing gene and to test its effect on yield and malting quality.ResultsDouble-haploid lines generated through a cross between a brh1.a mutant and the European elite malting cultivar Quench, showed good malting quality but a decrease in yield. Especially the activities of the starch degrading enzymes β-amylase and free limit dextrinase were high. A syntenic approach comparing markers in barley to those in rice (Oryza sativa L.), sorghum (Sorghum bicolor Moench) and brachypodium (Brachypodium distachyon P. Beauv) helped us to identify Brh1 as an orthologue of rice D1 encoding the Gα subunit of a heterotrimeric G protein. We demonstrated that Brh1 is allelic to Ari-m. Sixteen different mutant alleles were described at the DNA level.ConclusionsMutants in the Brh1 locus are deficient in the Gα subunit of a heterotrimeric G protein, which shows that heterotrimeric G proteins are important regulators of culm length in barley. Mutant alleles do not have any major negative effects on malting quality.