CYSTEINE BIOSYNTHESIS IN PLANTS TAKES PLACE IN THE THREE CELLULAR COMPARTMENTS WITH AUTONOMOUS PROTEIN BIOSYNTHESIS MACHINERY: cytosol, plastids and mitochondria. This sulfur-containing molecule is synthesized sequentially in these compartments by two enzymatic families, the serine acetyltransferases and the O-acetylserine(thiol) lyases. Each family consists of several isoforms that differ in subcellular localization and abundance. Why so many isoforms are required in plant cell for cysteine biosynthesis has remained unknown to date. The characterization of gene-specific knockout mutants has started to address this question. In our recent work, we have performed a detailed analysis of the Arabidopsis oas-a1 null mutant and showed that the antioxidant capacity of the cytosol is compromised, highlighting the contribution of cytosolic Cys in redox signaling.
Keywords: Arabidopsis; O-acetylserine(thiol)lyase; cysteine biosynthesis; redox regulation.