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7月14日清华大学生物论坛 - Richard Dixon
发布时间:2017-07-10关键字:

New Twists in the Biosynthesis of Condensed Tannins

 

 

Prof. Richard Dixon

University of North Texas


 

Abstract:

Proanthocyanidins (PAs) are the second most abundant plant polyphenolic compounds after lignin. PAs affect taste, mouth feel and astringency of many fruits, wines and beverages, have been associated with reduced risks of cardiovascular disease, cancer and Alzheimer's disease, can improve nutrition and prevent bloat in ruminant animals and enhance soil nitrogen retention. PAs are oligomers and polymers of flavan-3-ols, primarily (-)-epicatechin and (+)-catechin, but the mechanism by which the monomers polymerize and become insoluble is currently unknown. Leucoanthocyanidin reductase (LAR) has been shown to convert leucocyanidin to (+)-catechin. Here, we report that loss of function of LAR in the model legume Medicago truncatula leads unexpectedly to loss of soluble epicatechin-derived PAs, increased levels of insoluble PAs, and accumulation of 4β-(S-cysteinyl)-epicatechin, which provides the 4→8 linked extension units during non-enzymatic PA polymerization. LAR converts 4β-(S-cysteinyl)-epicatechin back to epicatechin, the starter unit in PAs, thereby regulating the relative proportions of starter and extension units and consequently the degree of PA oligomerization.



Time: July 14th, 2017, 10:00 am

Venue: New Biology Building, Room 143

Host: Dr. Qiao Zhao

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