Arabidopsis ACYL-ACTIVATING ENZYME 9 (AAE9) encoding an isobutyl-CoA synthetase is a key factor connecting branched-chain amino acid catabolism with iso-branched wax biosynthesis

Shipeng Li, Xianpeng Yang, Haodong Huang, Rong Qiao, Matthew A. Jenks, Huayan Zhao, L. Shiyou

Research output: Contribution to journalArticlepeer-review

Abstract

Iso-branched wax compounds are well known in plants, but their biosynthetic pathways are still mostly unknown. It has been speculated that branched waxes are derived from branched-chain amino acid (BCAA) catabolism, but the evidence for this is very limited. Gas chromatography-flame ionisation detection (GC-FID) analysis revealed that mutations in two subunits of the branched-chain ketoacid dehydrogenase (BCKDH) complex, a key enzyme complex in the degradation of BCAAs, significantly decreased the amounts of branched wax compounds, indicating that BCAA degradation may be integral to the synthesis of iso-branched wax. Substrate feeding studies further revealed that the metabolic precursor of iso-branched wax compounds is isobutyric acid (iBA), which is derived from valine degradation in Arabidopsis. We also isolated a novel mutant and found that its branched wax deficient phenotype could not be rescued by iBA. Map-based cloning together with complementation analysis revealed that mutation in ACYL-ACTIVATING ENZYME 9 (AAE9) is responsible for this phenotype. Genetic and enzyme activity analysis demonstrated that AAE9 is located downstream of the BCAA degradation pathway, and that it activates iBA to isobutyryl-CoA for use on branched wax synthesis. Taken together, our study demonstrates that AAE9 is a key factor connecting BCAA catabolism with branched wax biosynthesis.

Original languageEnglish (US)
Pages (from-to)2458-2470
Number of pages13
JournalNew Phytologist
Volume233
Issue number6
DOIs
StatePublished - Mar 2022

Keywords

  • Arabidopsis
  • acyl-activating enzyme
  • branched-chain amino acid
  • iso-branched wax
  • isobutyric acid

ASJC Scopus subject areas

  • Physiology
  • Plant Science

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