Redox sensitivity of proteins encoded by the Low expression of OSmotically responsive genes 2 locus in Arabidopsis thaliana

To fully exploit their photosynthetic apparatus and tolerate diverse environmental conditions, plants have developed various mechanisms to ensure an efficient management of reactive oxygen and nitrogen species. These small molecules play an important signaling function through redox-dependent post-translational modifications. Some modifications, such as S-glutathionylation, have a protective role against irreversible oxidation of protein thiols as well as implications in the regulation of protein activity and function. This research investigates redox sensitivity of proteins encoded by the Low expression of OSmotically responsive genes 2 gene of Arabidopsis thaliana. This gene is transcribed into an mRNA from which two proteins can be differentially translated. The first is a cytosolic enolase enzyme responsible for most of the cellular phosphoenolpyruvate production. The second is a transcription factor implicated in the regulation of cold response. Recombinant versions of both proteins were produced and subjected to in vitro assays in order to evaluate their sensibility to redox conditions. In spite of their divergent functions, these proteins exhibit some similarities in their sensitivity to oxidative conditions. In particular, our results support the existence of a covalent modification with glutathione for both proteins. This post-translational modification was shown to affect enolase activity and this effect was reversed using a cytosolic glutaredoxin. Efforts are currently underway to identify the cysteine residues that are targeted by redox modification on both proteins using LC-MS/MS and site directed mutagenesis approaches. In the end, this research could lead to a better understanding of the plant primary metabolism regulation in response to oxidative stress.