Novel Insight into the Regulation of GSH Biosynthesis in Higher Plants

Abstract

In higher plants, the redox-active tripeptide glutathione (GSH) fulfills a plethora of functions. These include its pivotal role for maintaining the cellular redox poise and its involvement in detoxification of heavy metals and xenobiotics. Intimately linked to these functions, GSH also acts as a cellular signal, mediating control of enzyme and/or regulatory protein activities, either directly or via glutaredoxins. The redox potential of the GSH/GSSG couple is not only affected by the GSH/GSSG ratio but also by changes in GSH synthesis and/or degradation. As this couple operates as redox buffer in several cellular compartments, the regulation of GSH biosynthesis and transport (both intra- and intercellularly) are fundamental to the maintenance of cellular redox homeostasis during plant development and, even more so, when plants are exposed to biotic or abiotic stress. This review highlights novel aspects of GSH biosynthesis and transport with a focus on the regulation of the GSH1 (= gamma-glutamylcysteine synthetase) enzyme. Interestingly, GSH1 appears to be exclusively confined to the plastids, whereas the second biosynthetic enzyme, GSH2, is predominantly localized in the cytosol. GSH1 expression and enzyme activity are under multiple controls, extending from transcriptional regulation to post-translational redox control. Now that the plant GSH1 protein structure has been solved, the molecular basis of GSH1 function and redox regulation can be addressed. The review concludes with a discussion of the simultaneous changes observed for GSH synthesis, transport, and metabolism during Cd-induced phytochelatin accumulation.

Potassium-induced alleviation of salinity stress in Brassica campestris L.

“…AsA-GSH-cycle metabolism is an essential mechanism of plant resistance under stressful conditions [38,41]. Glutathione removes excess H 2 O 2 [42] and lipid peroxides keep ROS under control [43]. APX detoxifies H 2 O 2 into water using AsA as the major substrate where GSH continuously regenerates AsA from DHA, the oxidized form, via the AsA-GSH cycle.…”

Effect of MgSO₄ nutrition on Theobroma cacao L. susceptibility to Phytophthora megakarya infection

“…Therefore, it could be assumed that sulphate supplied into soil led to an increase in the glutathione pool in T. cacao plant tissues; and the high pool of glutathione in tissues participates in the tolerance/resistance of cocoa genotypes (hybrids) to P. megakarya. This finding with T. cacao reminds the redox-active properties of glutathione (GSH/ GSSH) which fulfils protective functions when plants are exposed to biotic or abiotic stress (Rausch et al 2007). Moreover, Bloem et al (2004Bloem et al ( , 2007 reported that the infection of Brassica napus L. with Pyrenopeziza brassicae increased cysteine and glutathione contents, as well as the activity of l-cysteine desulfhydrase.…”

Friend or Foe? Exploring the Factors that Determine the Difference Between Positive and Negative Effects on Photosynthesis in Response to Insect Herbivory

“…Moreover, H 2 O 2 diffusion was shown to increase concomitantly with light intensity and time of illumination (Mubarakshina et al, 2010). Additional observations have suggested that glutathione, whose synthesis is affected by changes in photosynthesis, may also act as a plastid signal that controls expression of stress defense genes in the nucleus (Wachter et al, 2005;Mullineaux & Rausch, 2005;Rausch et al, 2007).…”