Submitted to: Plant Biology
Publication Type: Abstract Only
Publication Acceptance Date: 4/1/2005
Publication Date: 7/1/2005
Citation: Whittaker, D., Triplett, B.A., Rintelmann, A., Carter, C., Bryant, C., Puthigae, S., Phillips, J., Espinoza-Smith, C., Elborough, K. Functional analysis of a putative ryegrass leucoanthocyanidin reductase. Available from: http://probe.naluda.gov.8000/plant/index.html Plant Biology . Interpretive Summary:
Technical Abstract: Proanthocyanidins, also known as condensed tannins, are polymeric flavonoids that occur widely in plants and interact strongly with proteins. The presence of condensed tannins in the leaves of forage plants can protect ruminant animals against pasture bloat and improve nitrogen nutrition. However certain forage crops, including perennial ryegrass (Lolium perenne L.) and alfalfa (Medicago sativa L.) contain very low levels of tannins. Manipulation of flavonoid metabolism is therefore of great interest to the pastoral industries. Leucoanthocyanidin reductase (LAR) catalyses the conversion of 3,4-cis-leucocyanidin to catechin, which is thought to act as a monomeric ‘starter unit’ for tannin condensation. We cloned and sequenced a putative leucoanthocyanidin reductase (LAR) cDNA from the fibers of a high-proanthocyanidin line of cotton (Gossypium hirsutum L.). A putative ryegrass orthologue was identified in our Genethresher® genomic sequence database, based on similarity to the cotton gene and the publicly available Desmodium uncinatum LAR gene. Using an Agrobacterium-based protocol, ryegrass was transformed with a construct comprising the full-length ryegrass gene under the control of a CAMV 35S promoter. Elevated levels of a low molecular weight flavonoid compound in the leaves of primary transformants indicated increased LAR activity. Overall proanthocyanidin levels remained low, consistent with a low rate of flux through the proanthocyanidin branch of the flavonoid pathway, and limiting levels of the leucocyanidin substrate.