Localization of A. thaliana class III peroxidases AT2G43480 and AT3G21770

Class III plant peroxidases are found in all land plants and lignification, suberization, and pathogen defense are three of the many functions served by these enzymes. The numerous peroxidase functions and the large multigenic families peroxidases are a part of have made it difficult to study class III peroxidases. The goal of this study was to determine the in vivo localization of Arabidopsis thaliana peroxidases At2g43480 and At3g21770 by using a fluorescent protein tag. Because both peroxidases have an endoplasmic reticulum signal peptide and lack a hydrophobic C-terminus, it was expected that both would be found at the cell wall. At2g43480 was not expressed in the cell wall and it may be involved in plant defense or modifying monolignols for suberization. At3g21770 was expressed in the cell wall of xylem tissue, lateral root cap cells, and columella cells, where it may be involved in lignification. In epidermal guard cells, At3g21770 was expressed intracellularly and may function in deposition of cell wall material in plasmodesmata to cytoplasmically isolate maturing guard cells. The possibility of At2g43480 involved in monolignol modifications and At3g21770 involved in lignification is significant because lignin is an abundant plant cell wall polymer and its regulation is beneficial to the paper pulping industry and to biofuel production