Structural and Functional Characterization of TomEP, a Tomato Extensin Peroxidase
Michael Held (United States)1 2; Zawar Hussain (United States)3; John W. Mishler-Elmore (United States)1; Abhijit Sukul (United States)1; Ahmed Faik (United States)2 3;
1 - Department of Chemistry and Biochemistry, Ohio University, Athens, OH 45701, USA; 2 - Molecular and Cellular Biology Program, Ohio University, Athens, OH 45701, USA; 3 - Department of Environmental & Plant Biology, Ohio University, Athens, OH 45701, USA;
Keywords: extensin; crosslinking; peroxidase;
Abstract Topics: Theme 5: Cell Wall Proteins
Type of Presentation: Oral Communication

Abstract text: Extensins (EXTs) comprise a diverse group of cell wall structural glycoproteins that undergo self-assembly and covalent crosslinking. Covalent crosslinking is mediated by EXT peroxidases (EPs) that polymerize EXT monomers to create a polymeric scaffold. Scaffold formation is important for plant growth and development, mechanical wounding, and pathogen response. Therefore, understanding EXT crosslinking and scaffold formation is crucial. Our previous work identified an EP from tomato (TomEP) that is predominantly expressed in roots. TomEP has been characterized in vitro, but its physiological role(s) in vivo has not been explored. Phenotypic and biochemical characterization of CRISPR mutant line (tomep_6) showed faster root growth phenotypes with higher apoplastic ROS and lower peroxidase activity in comparison with controls. Complementation successfully restored phenotypes. Subcellular localization of TomEP was explored using live-cell imaging in tobacco leaves. Consistent with prior work, TomEP appeared to be plasma membrane (PM)-localized. Addition of H2O2 co-substrate shifted the subcellular distribution of TomEP from PM to apoplast both in the presence and absence of EXT analog co-substrates. Furthermore, docking studies showed that various EXT crosslinking motifs and their crosslinked products fit well into TomEP's active site. These data reveal interesting implications regarding the regulation of EXT scaffold formation in vivo.