Figure 1. Cysteine-generated sulfide in the cytosol regulates autophagy. In the Arabidopsis plant cell there are different subcellular compartments where sulfide is generated: chloroplast, mitochondria and cytosol. In the chloroplast, sulfide is produced by photosynthetic sulfate reduction and its predominant charged HS^- form requires an active transporter (unidentified to date) to cross the envelope. In the mitochondria, sulfide is recycled for cyanide detoxification and is also predominantly present in the charged HS^- form. In the cytosol, DES1 is responsible for the generation of sulfide. Irrespective of nutrient conditions, the sulfide generated in the cytosol behaves as a signaling molecule acting as a repressor of autophagy.