Mechanistic basis for the emergence of EPS1 as a catalyst in salicylic acid biosynthesis of Brassicaceae
Michael P. Torrens-Spence, Jason O. Matos, Tianjie Li, David W. Kastner, Colin Y. Kim, Ziqi Wang, Christopher M. Glinkerman, Jennifer Sherk, Heather J. Kulik, Yi Wang, Jing‐Ke Weng
Abstract
Salicylic acid (SA) production in Brassicaceae plants is uniquely accelerated from isochorismate by EPS1, a newly identified enzyme in the BAHD acyltransferase family. We present crystal structures of EPS1 from Arabidopsis thaliana in both its apo and substrate-analog-bound forms. Integrating microsecond-scale molecular dynamics simulations with quantum mechanical cluster modeling, we propose a pericyclic rearrangement lyase mechanism for EPS1. We further reconstitute the isochorismate-derived SA biosynthesis pathway in Saccharomyces cerevisiae, establishing an in vivo platform to examine the impact of active-site residues on EPS1 functionality. Moreover, stable transgenic expression of EPS1 in soybean increases basal SA levels, highlighting the enzyme’s potential to enhance defense mechanisms in non-Brassicaceae plants lacking an EPS1 ortholog. Our findings illustrate the evolutionary adaptation of an ancestral enzyme’s active site to enable a novel catalytic mechanism that boosts SA production in Brassicaceae plants. Torrens-Spence et al. reveal how plants in the cabbage family uniquely accelerate production of salicylic acid, a key defense hormone, through evolution of a specialized enzyme called EPS1. This finding could help enhance disease resistance in other crops.