Expression of an Antirrhinum dihydroflavonol reductase gene results in changes in condensed tannin structure and accumulation in root cultures of Lotus corniculatus (bird's foot trefoil)

Condensed tannins (proanthocyanidins) are an important factor in the nutritive and dietary quality of many forage crops. We report here experiments aimed at altering the levels and monomer composition of condensed tannins (CTs) in hairy root cultures of Lotus corniculatus (bird's foot trefoil) using genetic manipulation. An Antirrhinum majus dihydroflavonol reductase (DFR) cDNA was expressed in sense in L. corniculatus and CT levels in transgenic root cultures were analysed. Two co-transformed lines were noted with decreased CT content relative to controls and these levels were comparable with antisense-DFR phenotypes. In ADFR10, a co-transformed line with the highest CT levels, CT structure was altered in a manner consistent with the substrate specificity of the introduced gene; that is an increase in pro-pelargonidin monomers noted after hydrolysis of CTs. RT-PCR confirmed the expression of endogenous DFR gene(s) in both putatively co-suppressed lines and also in ADFR10. Analysis of selected root culture lines indicated that the monomer composition of CTs did not change during growth and development but that levels of CTs varied in a regulated manner.