AUTHOR=Roldan Marissa B. , Cousins Greig , Muetzel Stefan , Zeller Wayne E. , Fraser Karl , Salminen Juha-Pekka , Blanc Alexia , Kaur Rupinder , Richardson Kim , Maher Dorothy , Jahufer Zulfi , Woodfield Derek R. , Caradus John R. , Voisey Christine R. 

TITLE=Condensed Tannins in White Clover (Trifolium repens) Foliar Tissues Expressing the Transcription Factor TaMYB14-1 Bind to Forage Protein and Reduce Ammonia and Methane Emissions in vitro

JOURNAL=Frontiers in Plant Science

VOLUME=Volume 12 - 2021

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.777354

DOI=10.3389/fpls.2021.777354

ISSN=1664-462X

ABSTRACT=Grazing ruminants contribute to global climate change through enteric methane and nitrous oxide emissions. However, animal consumption of the plant polyphenolics, proanthocyanidins or condensed tannins (CTs), can decrease both methane emissions and urine nitrogen levels leading to reduced nitrous oxide emissions, and concomitantly increase animal health and production. CTs are largely absent in the foliage of important temperate pasture legumes, such as white clover (Trifolium repens), but found in flowers and seed coats. Attempts at enhancing levels of CT expression in white clover leaves by mutagenesis and breeding have not been successful. However, transformation of white clover with the TaMYB14-1 transcription factor from Trifolium arvense, has resulted in the production of CTs in leaves up to 1.2% of dry matter (DM), and two generations of breeding elevated foliar CTs to >2.0% of DM. The CTs consisted predominantly of prodelphinidins (PD, 75-93%) and procyanidins (PC, 17-25%) and had a mean degree of polymerization (mDP) of approximately 10 flavan-3-ol-units. In vitro studies showed that foliar CTs bound to bovine serum albumin & white clover proteins at pH 6.5 and were released at pH 2.0-2.5. Using rumen in vitro assays, white clover leaves containing CTs of 1.6 – 2.4% of DM reduced methane production by 19% and ammonia production by 60% relative to non-transformed wild type (WT) controls after 6 hours of incubation. These results provide valuable information for further studies using CT expressing white clover leaves for bloat prevention and reduced greenhouse gas emissions in vivo.