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 LsBAHD3 and LsAAE3 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 LsBAHD3 act as BOS, while LsAAE3 function as oxalyl-CoA synthetase to catalyse/promote β-ODAP biosynthesis. Further comparison and verification of LsBAHD3-specific and LsAAE3-specific protein interactome suggested that the LsBAHD3-LsAAE3 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.