Genetic Manipulation of Condensed Tannins in Higher Plants1

Abstract

We have produced and analyzed transgenic birdsfoot trefoil (Lotus corniculatus L.) plants harboring antisense dihydroflavonol reductase (AS-DFR) sequences. In initial experiments the effect of introducing three different antisense Antirrhinum majus L. DFR constructs into a single recipient genotype (S50) was assessed. There were no obvious effects on plant biomass, but levels of condensed tannins showed a statistical reduction in leaf, stem, and root tissues of some of the antisense lines. Transformation events were also found, which resulted in increased levels of condensed tannins. In subsequent experiments a detailed study of AS-DFR phenotypes was carried out in genotype S33 using pMAJ2 (an antisense construct comprising the 5 half of the A. majus cDNA). In this case, reduced tannin levels were found in leaf and stem tissues and in juvenile shoot tissues. Analysis of soluble flavonoids and isoflavonoids in tannin down-regulated shoot tissues indicated few obvious default products. When two S33 AS-DFR lines were outcrossed, there was an underrepresentation of transgene sequences in progeny plants and no examples of inheritance of an antisense phenotype were observed. To our knowledge, this is the first report of the genetic manipulation of condensed tannin biosynthesis in higher plants.

Molecular Cloning and Characterization of Two Genes Encoding Dihydroflavonol-4-Reductase from Populus trichocarpa

“…To date, the biosynthetic pathways for CTs and a large number of polyphenolic compounds have been well established [7] , [22] . DFR encodes a key enzyme in the later steps of CT synthesis in plants, and overexpression of a DFR gene in the forage legume Lotus corniculatus resulted in an alteration of CT levels [48] , [49] . To further determine the function of PtrDFR s in the CT biosynthetic pathway, their ORFs, flanked by the 35S promoter, were introduced into P. tomentosa Carr.…”

Evidence for enzyme complexes in the phenylpropanoid and flavonoid pathways

“…Some success has been achieved by introducing heterologous genes encoding enzymes with different substrate specificities, such as the classic experiment using the maize DFR gene to produce petunias with a brick‐red color and the more recent use of petunia F3′5′H and DFR genes to produce violet carnations (reviewed in Tanaka et al 1998). On the other hand, antisense ampproaches using DFR have been successful for downregulating condensed tannin production in birdsfoot trefoil (Robbins et al 1998), albeit at the expense of anthocyanin biosynthesis. Controlled misexpression of ferulate 5‐hydroxylase in the sinapate pathway shows promise for modulation of lignin biosynthesis (Meyer et al 1998).…”

Molecular Cloning and Functional Characterization of a Dihydroflavonol 4-Reductase from Vitis bellula

“…Particularly, anthocyanins are one of the richest plant natural pigments with significant economic values in the horticulture industry [ 6 , 10 , 11 , 12 , 13 ]. Since the first success of Petunia flower color engineering was achieved using the first DFR cDNA cloned from maize [ 13 ], multiple homologs have been cloned to engineer anthocyanins [ 1 , 14 , 15 ] and proanthocyanidins [ 16 , 17 ]. DFR also plays a key role in transcription factor-based anthocyanin engineering.…”