Fig. 6.
Schematic model of the sulfur reallocation pathway from GLs in A. thaliana. Sulfur atoms derived from sulfate and thioglucoside groups in the GL structure are highlighted in orange and yellow, respectively. Both sulfur atoms could ultimately be reintegrated into Cys biosynthesis as S2-. Sulfates produced by the GL hydrolysis can be directly incorporated into primary sulfur metabolism as substrates (1). The sulfur atom in the thioglucoside group is relayed to RA through GL catabolism including the conjugation of ITC with GSH (2), which is finally released from RA and then reintegrated into the primary sulfur metabolism (3). GSH and its amino acid components (Gly, Glu, and Cys) form a catabolic loop during ITC processing (4). Further processing of the amine product may also mobilize the Met-derived sulfur at the side chain of aliphatic GLs (5). Contribution of the nitrile pathway (6) remains unclear, despite its potential to release two sulfur atoms directly through the initial hydrolytic reactions. APS, adenosine-5′-phosphosulfate; BSAS, beta-substituted alanine synthase; GST, glutathione S-transferase.