Updated project metadata. In this work we want to shed light on the functions of apoplastic gamma-glutamyl transferase/transpeptidase (GGT; E.C. 2.3.2.2) in the plant???s adaptation to the environment. We investigate the effects of UV-B radiation as an oxidizing stress condition affecting the apoplastic environment in wild type Arabidopsis and a previously-characterized ggt1 knockout mutant line.