RT Journal Article
SR Electronic
T1 Structural and Functional Analyses Explain Pea KAI2 Receptor Diversity and Reveal Stereoselective Catalysis During Signal Perception
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 2021.01.06.425465
DO 10.1101/2021.01.06.425465
A1 Angelica M. Guercio
A1 Salar Torabi
A1 David Cornu
A1 Marion Dalmais
A1 Abdelhafid Bendahmane
A1 Christine Le Signor
A1 Jean-Paul Pillot
A1 Philippe Le Bris
A1 François-Didier Boyer
A1 Catherine Rameau
A1 Caroline Gutjahr
A1 Alexandre de Saint Germain
A1 Nitzan Shabek
YR 2021
UL http://biorxiv.org/content/early/2021/08/30/2021.01.06.425465.abstract
AB KAI2 are plant α/β hydrolase receptors, which perceive smoke-derived butenolide signals (karrikins) and putative endogenous, yet unidentified phytohormones (KAI2-ligands, KLs). The number of functional KAI2 receptors varies among plant species. It has been suggested that KAI2 gene duplication and sub-functionalization plays an adaptative role for diverse environments or ligand diversification by altering the receptor responsiveness to specific KLs. Legumes represent one of the largest families of flowering plants and contain many essential agronomic crops. Prior to legume diversification, KAI2 underwent duplication, resulting in KAI2A and KAI2B. Integrating plant genetics, ligand perception and enzymatic assays, and protein crystallography, we demonstrate that Pisum sativum KAI2A and KAI2B act as receptors and enzymes with divergent ligand stereoselectivity. KAI2B has a stronger affinity than KAI2A towards the KAI2-ligand (-)-GR24 and remarkably hydrolyses a broader range of substrates including the strigolactone-like isomer (+)-GR24. We determine the crystal structures of PsKAI2B in apo and butenolide-bound states. The biochemical and structural analyses as well as recorded mass spectra of KAI2s reveal a transient intermediate on the catalytic serine and a stable adduct on the catalytic histidine, further illuminating the role of KAI2 not only as receptors but also as bona fide enzymes. Our work uncovers the stereoselectivity of ligand perception and catalysis by evolutionarily diverged KAI2 receptors in KAR/KL signaling pathways and proposes adaptive sensitivity to KAR/KL and strigolactone phytohormones by KAI2B.Competing Interest StatementN.S. has an equity interest in Oerth Bio and serves on the company Scientific Advisory Board. The work and data submitted here have no competing interests or other interests that might be perceived to influence the results or discussion reported in this paper.