3-O-glycosylation of kaempferol restricts the supply of the benzenoid precursor of ubiquinone (Coenzyme Q) in Arabidopsis thaliana

Authors: SOUBEYRAND, ERIC - University Of Florida; LATIMER, SCOTT - University Of Florida; BERMERT, ANN - University Of Florida; KEENE, SHEA - University Of Florida; JOHNSON, TIMOTHY - University Of Florida; SHIN, DOOSAN - University Of Florida; Block, Anna; COLQUHOUN, THOMAS - University Of Florida; SHAEFNNER, ANTON - German Research Center For Environmental Health; KIM, JEONGIM - University Of Florida; BASSET, GILLES - University Of Florida

Submitted to: Phytochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/9/2021
Publication Date: 3/21/2021
Citation: Soubeyrand, E., Latimer, S., Bermert, A.C., Keene, S.A., Johnson, T.S., Shin, D., Block, A.K., Colquhoun, T.A., Shaefnner, A.R., Kim, J., Basset, G.J. 2021. 3-O-glycosylation of kaempferol restricts the supply of the benzenoid precursor of ubiquinone (Coenzyme Q) in Arabidopsis thaliana. Phytochemistry. 186,112738. https://doi.org/10.1016/j.phytochem.2021.112738.
DOI: https://doi.org/10.1016/j.phytochem.2021.112738

Interpretive Summary: Coenzyme Q is an important compound for both human and plant health. It plays a vital role in respiration and has strong antioxidative properties that protect plants and animals against harmful conditions. Increased production of coenzyme Q in plants can increase their nutritional value and potentially allow them to cope better with adverse conditions such as flooding, cold or drought. As a first step towards producing plants with higher amounts of coenzyme Q, University of Florida scientists in collaboration with a USDA-ARS scientist at the Center for Medical, Agricultural, and Veterinary Medicine in Gainesville, FL have identified genes that limit the availability of one of its building blocks. Suppression of the function of these genes in plants resulted in a 160% increase in coenzyme Q production. Identification of crop varieties that have natural mutants in these genes would therefore provide important breeding tools to produce plants with elevated coenzyme Q.

Technical Abstract: Ubiquinone (Coenzyme Q) is a vital respiratory cofactor and antioxidant in eukaryotes. The recent discovery that kaempferol serves as a precursor for ubiquinone's benzenoid moiety both challenges the conventional view of flavonoids as 'specialized' metabolites, and offers new prospects for engineering ubiquinone in plants. Here, we present evidence that Arabidopsis mutants lacking kaempferol 3-O-rhamnosyltransferase (ugt78d1) and kaempferol 3-Oglucosyltransferase (ugt78d2) activities display increased de novo biosynthesis of ubiquinone and increased ubiquinone content. These data are congruent with the proposed model that unprotected C-3 hydroxyl of kaempferol triggers the oxidative release of its B-ring as 4-hydroxybenzoate, which in turn is incorporated into ubiquinone. Ubiquinone content in the ugt78d1/ugt78d2 double knockout represented 160% of wild-type level, matching that achieved via exogenous feeding of 4-hydroxybenzoate to wild-type plants. This suggests that 4- hydroxybenzoate is no longer limiting ubiquinone biosynthesis in the ugt78d1/ugt78d2 plants. Evidence is also shown that the glucosylation of 4-hydroxybenzoate as well as the conversion of the immediate precursor of kaempferol, dihydrokaempferol, into dihydroquercetin do not compete with ubiquinone biosynthesis in Arabidopsis.