Constitutive expression of THIOGLUCOSIDE GLUCOHYDROLASE 1 (TGG1) decreases intercellular trafficking in Arabidopsis thaliana

Plasmodesmata (PD) are pores that traverse plant cell walls, providing a route for intercellular trafficking of essential metabolites, nutrients, and signaling molecules between adjacent plant cells, thereby aiding communication. The increased size exclusion limit 2 (ise2) mutant of Arabidopsis thaliana has an increased abundance of branched PD, as well as a greater flux of intercellular trafficking. A search for proteins that interact with ISE2 identified THIOGLUCOSIDE GLUCOHYDROLASE 2 (a myrosinase). A. thaliana also encodes a second, closely-related myrosinase, TGG1. Myrosinases are enzymes that catalyze the hydrolysis of glucosinolates, a type of secondary metabolite that are amino acid derivatives. The breakdown of glucosinolates by myrosinases and related enzymes produces isothiocynates, toxic compounds important for plant defense. While ISE2 and TGG2 interact, the effects of this interaction are unclear, and understanding this relationship was the goal of this study. We measured intercellular trafficking of green fluorescent protein (GFP) in plants with constitutive strong expression of TGG1. Intercellular trafficking decreased in plants with increased TGG1 expression. This result suggests that TGG1, and probably its substrates or products, could have important roles in controlling intercellular trafficking via PD. We will also explore how this decrease in intercellular trafficking affects plant defense.