FIG. 3.

Overview of plastid processes subject to redox regulation via (A) the Fdx/Trx or (B) the NADPH/NTRC system. While the Fdx/Trx system is directly linked to light-driven electron transport, the NADPH/NTRC system is linked to photoreduced Fdx via Fdx-NADP-reductase (FNR) and to sugar metabolism via the OPP in the dark. An overview of the enzymes and proteins that have been found to be subject to redox regulation by these systems as well as the respective references are given in Table 1. NTRC is a bifunctional enzyme that combines both a NADP-Trx reductase and a Trx in a single polypeptide. Compared with Fdx-linked Trxs, there is only little information on possible targets of NTRC. More studies are needed to identify further plastidial processes that are subject to redox regulation by NTRC. For Abbreviations, see Abbreviations Used section. To see this illustration in color, the reader is referred to the web version of this article at www.liebertpub.com/ars