ABSTRACT
I. INTRODUCTION Glutathione (GSH), the tripeptide -glutamylcysteinyl glycine, is ubiquitous and the most abundant nonprotein thiol in plant cells [1]. The unique structure of GSH gives this molecule the exceptional stability, high water solubility, and redox properties that make GSH well suited to perform diverse functions. GSH is proposed to play important roles in defense. These include scavenging reactive oxygen species (ROS) through the ascorbate-GSH cycle [2-5], detoxifying a variety of organic electrophilic contaminants through glutathione S-transferases [6] and heavy metals through the phytochelatins (PCs) synthesized by PC synthase [7-9] upon heavy metal exposure [10,11]. In addition, GSH is important in organic sulfur storage, transport, and metabolism [12].
