RESEARCH-PGR: Defining the Sumoylation System in Maize and Its Roles in Stress Protection

Washington University, Saint Louis MO

Investigators

Abstract

Crop plants require suitable mechanisms to survive and perform well under unfavorable environments in order to maintain high productivity. Recently, a small protein called SUMO was discovered, and it appears to protect plants against environmental stresses like heat and drought. Recent experiments with plants exposed to environmental stresses have shown that the SUMO protein may significantly affect how genes are expressed under those unfavorable conditions. The SUMO protein becomes rapidly and reversibly attached to a group of proteins that affect the pattern of gene expression during environmental stress. The goals of this project are to understand the functions of SUMO during stress and determine whether its manipulation in crops might provide novel approaches to improve stress tolerance. This project will characterize the mode of action of the SUMO protein, and identify all the other proteins that interact with SUMO under stress. To help understand how SUMO helps maize survive stress, we will also determine why maize mutants missing key components are now hypersensitive to stress. Collectively, this fundamental research will identify key points in maize SUMOylation that can be exploited to improve stress protection, not only in maize but in other crops as well. This project will train postdocs, graduate students, and undergraduates at Washington University in St. Louis. It will also develop patentable technologies related SUMO and stress tolerance that can sustainably enhance food and biofuel crop yield. SUMO is an influential regulator in eukaryotes that works following its post-translation addition to other intracellular proteins. Recent studies with Arabidopsis discovered that SUMOylation selectively modifies a number of critical regulators during stress that impact chromatin accessibility, DNA/histone modification, transcription, nuclear pore function, and mRNA processing/export. Their combined activities imply that stress-induced SUMOylation helps plants reversibly adjust chromatin architecture and the resulting RNA landscape to better survive adverse conditions. Unfortunately, appreciation of SUMO is lacking for crops, thus precluding rational redesign for agricultural benefit. To overcome this knowledge gap, this project will define how SUMOylation works in maize (Zea mays), using as essential backdrops our recent success in creating germplasm to study SUMO via proteomic approaches. This project will: (i) describe how the maize SUMO system works biochemically and responds to various environmental challenges, (ii) combine transgenic lines expressing tagged SUMOs with established mass spectrometric methods to define the maize 'SUMOylome' and its linkage sites, (iii) determine quantitatively how the SUMOylation status of individual targets is impacted by stress, and (iv) understand how SUMO helps maize survive adverse environments through the phenotypic and biochemical analyses of system mutants generated by either Mu transposition or CRISPR/Cas9 gene editing technologies. Collectively, this project will generate much-needed reagents, techniques, and mutants that will help define how SUMO reorganizes maize chromatin and its transcriptome during stress, and identify key points in SUMOylation that can be manipulated to improve stress protection in many crop species.