Divergent evolution of extreme production of variant plant monounsaturated fatty acids

Authors

Lu Gan, University of Nebraska - LincolnFollow
Kiyoul Park, University of Nebraska-LincolnFollow
Jin Chai, University of Nebraska-Lincoln
Evan M. Updike, University of Nebraska-Lincoln
Hyojin Kim, University of Nebraska-LincolnFollow
Adam Voshall, University of Nebraska-Lincoln
Sairam Behera, University of Nebraska-LincolnFollow
Xiao-Hong Yu, Stony Brook University
Yuanheng Cai, Stony Brook University
Chunyu Zhang, Huazhong Agricultural University
Mark A. Wilson, Department of BiochemistryFollow
Jeffrey P. Mower, University of Nebraska-LincolnFollow
Etsuko Moriyama, University of Nebraska-LincolnFollow
Chi ZhangFollow
Sireewan Kaewsuwan, Prince of Songkla University
Qun Liu, University of Nebraska-Lincoln
John Shanklin, University of Nebraska-Lincoln
Edgar B. Cahoon, University of Nebraska - LincolnFollow

Date of this Version

6-12-2022

Citation

PNAS 2022 Vol. 119 No. 30 e2201160119 https://doi.org/10.1073/pnas.2201160119

Comments

U.S. government works are not subject to copyright.

Abstract

Metabolic extremes provide opportunities to understand enzymatic and metabolic plasticity and biotechnological tools for novel biomaterial production. We discovered that seed oils of many Thunbergia species contain up to 92% of the unusual monounsaturated petroselinic acid (18:1Δ6), one of the highest reported levels for a single fatty acid in plants. Supporting the biosynthetic origin of petroselinic acid, we identified a Δ6-stearoyl-acyl carrier protein (18:0-ACP) desaturase from Thunbergia laurifolia, closely related to a previously identified Δ6-palmitoyl-ACP desaturase that produces sapienic acid (16:1Δ6)- rich oils in Thunbergia alata seeds. Guided by a T. laurifolia desaturase crystal structure obtained in this study, enzyme mutagenesis identified key amino acids for functional divergence of Δ6 desaturases from the archetypal Δ9-18:0-ACP desaturase and mutations that result in nonnative enzyme regiospecificity. Furthermore, we demonstrate the utility of the T. laurifolia desaturase for the production of unusual monounsaturated fatty acids in engineered plant and bacterial hosts. Through stepwise metabolic engineering, we provide evidence that divergent evolution of extreme petroselinic acid and sapienic acid production arises from biosynthetic and metabolic functional specialization and enhanced expression of specific enzymes to accommodate metabolism of atypical substrates.