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ARS Home » Southeast Area » Gainesville, Florida » Center for Medical, Agricultural and Veterinary Entomology » Chemistry Research » Research » Publications at this Location » Publication #417510
Research Project: Regulation, Biosynthesis, and Function of Plant Chemical Defenses and their Role in Climate-Resilient Agriculture

Location: Chemistry Research

Title: The origin and metabolic fate of 4-hydroxybenzoate in Arabidopsis

Author
item BATYRSHINA, ZHANIA - University Of Florida
item Block, Anna
item BASSET, GILES - University Of Florida

Submitted to: Planta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/8/2024
Publication Date: 11/19/2024
Citation: Batyrshina, Z., Block, A.K., Basset, G.J. 2024. The origin and metabolic fate of 4-hydroxybenzoate in Arabidopsis. Planta. 260,144. https://doi.org/10.1007/s00425-024-04572-2.
DOI: https://doi.org/10.1007/s00425-024-04572-2

Interpretive Summary: 4-hydroxybenzoate (4-HB) is an essential chemical component of the plant cell wall and a precursor for the biosynthesis of the important respiratory cofactor and antioxidant Coenzyme Q. There has been long standing interest in 4-HB as a target molecule for plant metabolic engineering, both to boost Coenzyme Q level in crops and as an alternative to petrochemical synthesis for the production of antimicrobials, pharmaceuticals, and copolyesters. Studies by ARS scientists from Gainesville Florida, and scientists from the University of Florida have revealed the mechanisms plants use to produce 4-HB in different plant parts such as flowers, leaves and roots. These studies provide vital information for the bioengineering of 4-HB in plants.

Technical Abstract: 4-hydroxybenzoate (4-HB) is a vital precursor for a number of plant primary and specialized metabolites, as well as for the assembly of the plant cell wall. In Arabidopsis, it is known that 4-HB is derived independently from phenylalanine and tyrosine, and that the metabolism of phenylalanine into 4-HB proceeds via at least two biosynthetic routes: the ß-oxidation of p-coumarate and the peroxidative cleavage of kaempferol. The precise contribution of these precursors and branches to 4-HB production, however, is not known. Here we combined isotopic feeding assays, reverse genetics, and quantification of soluble – i.e. free and glycosylated– and cell wall-bound 4-HB to determine the respective contributions of phenylalanine, tyrosine, ß-oxidation of p-coumarate, and peroxidative cleavage of kaempferol to 4-HB biosynthesis in Arabidopsis tissues. Over 90% of 4-HB was found to originate from phenylalanine in both leaves and roots. Soluble 4-HB level varied significantly between organs, while the proportion of cell wall-bound 4-HB was relatively constant. Glycosylated and cell wall-bound 4-HB were the most and least abundant forms, respectively. Flowers displayed the highest specific content of 4-HB, while free 4-HB was not detected in roots. Although p-coumarate ß-oxidation and kaempferol catabolism were found to both contribute to the supply of 4-HB in all tissues, the proportion of kaempferol-derived 4-HB was higher in roots than in leaves and flowers. Within the ß-oxidative branch, p-coumaroyl-CoA ligase 4-CL8 (At5g38120) bore a preponderant role in the production of soluble and cell wall-bound 4-HB in leaves, while pcoumaroyl-CoA ligase At4g19010 appeared to control the biosynthesis of soluble 4-HB in flowers. Furthermore, analysis of a series of Arabidopsis T-DNA mutants corresponding to the three major UDP-glucosyltransferases known to act on 4-HB in vitro (UGT75B1, UGT89B1, and UGT71B1) showed that none of these enzymes appeared in fact to have a significant role in the glycosylation of 4-HB in vivo.