The LsBAHD3‐LsAAE3 Module Catalyses Biosynthesis of β‐N‐Oxalyl‐L‐α,β‐Diaminopropionic Acid in Lathyrus sativus and Pisum sativum

The neuroactive β ‐N‐oxalyl‐L‐ α , β ‐diaminopropionic acid ( β ‐ODAP) was first identified in Lathyrus sativus and present also in several Chinese traditional herbs including Panax notoginseng . It exhibit toxicological effects as the causative agent of neurolathyrism when L. sativus was over‐consumed under drought‐triggered famines or pharmacological effects including neuroprotection and wound healing. Determinating of β ‐ODAP synthetase (BOS) will accelerate plant improvement and utilisation of those species containing β ‐ODAP. In this report, trace level of β ‐ODAP was confirmed in several cultivars of Pisum sativum , a close relative of L. sativus . Functions of Ls BAHD3 and Ls AAE3 were investigated via its transient expression in Nicotiana benthamiana , in vitro enzymatic activity assay and overexpression in hairy roots of L. sativus and P. sativum , etc. The results suggested that Ls BAHD3 act as BOS, while Ls AAE3 function as oxalyl‐CoA synthetase to catalyse/promote β ‐ODAP biosynthesis. Further comparison and verification of Ls BAHD3‐specific and Ls AAE3‐specific protein interactome suggested that the Ls BAHD3‐ Ls AAE3 module catalyses β ‐ODAP biosynthesis, and the ubiquitin/26S proteasome system is highly involved in the regulation of BOS and β ‐ODAP content and may be responsible for the different level of β ‐ODAP in L. sativus and P. sativum . These results provide valuable insight into the biochemical and genetic mechanisms of β ‐ODAP biosynthesis.