Parallel evolution of plant alkaloid biosynthesis from bacterial-like decarboxylases

Area of Science:

• Biochemistry
• Plant Science
• Enzymology

Background:

• Basic amino acids lysine and ornithine are precursors to important plant alkaloids.
• Alkaloid biosynthesis can occur through symmetric or nonsymmetric pathways.

Purpose of the Study:

• To identify enzymes responsible for the nonsymmetric pathway of alkaloid biosynthesis.
• To characterize the newly discovered enzymes and their evolutionary origins.

Main Methods:

• Transcriptomics and enzyme characterization (mutagenesis, isotope labeling) were used to identify key enzymes.
• Phylogenetic analysis was employed to trace the evolutionary history of these enzymes across plant lineages.
• Enzyme assays were performed to determine substrate specificity and catalytic mechanism.

Main Results:

• Discovery of ornithine/lysine/arginine decarboxy-oxidases (OLADOs), pyridoxal phosphate (PLP)-dependent enzymes catalyzing nonsymmetric alkaloid precursor synthesis.
• Identification of OLADOs in *Flueggea suffruticosa*, *Nicotiana tabacum*, and *Artemisia annua*.
• Demonstration that OLADOs evolved from ornithine/lysine/arginine decarboxylase-like family (OLADLs) via parallel evolution in plants, representing a new class of eukaryotic decarboxylases.

Conclusions:

• OLADOs represent a novel class of plant enzymes crucial for nonsymmetric alkaloid biosynthesis.
• The discovery of OLADOs expands the known enzymatic repertoire for alkaloid production in plants.
• Parallel evolution provides a powerful strategy for discovering functionally conserved genes and enzymes across diverse species.