OP10 Proteomic analysis of endogenous S-sulfhydration in Arabidopsis thaliana

Hydrogen sulfide has emerged as one of the gaseous transmitter family of signalling molecules and appears to play an important regulatory role in a large array of physiological an pathological processes in mammals [1] . In plants, hydrogen sulfide has been found to mediate increases in tolerance and protection against certain plant stresses and alleviates the inhibitory effects of copper, aluminum and boron stress on wheat germination and cucumber root elongation. Moreover, sulfide treatment improves heat tolerance in tobacco and increases plant resistance against fungal pathogens. In addition, sulfide has been recently discovered as a component of the abscisic acid signalling network in guard cells [2] , [3] . We have recently demonstrated that sulfide exerts a general effect on autophagy through negative regulation, in a way unrelated to nutrient deficiency, and has an important impact on the transcriptional regulation in Arabidopsis . These observations have been genetically linked through the analysis of null mutant alleles of Arabidopsis defective of the cytosolic l -cysteine desulfhydrase DES1 involved in the degradation of cysteine and the generation of hydrogen sulfide in this cellular compartment [4] , [5] . Protein S-sulfhydration of the thiol residue of cysteines has been proposed as a mechanism for transforming the sulfide signal into a biological response in analogy with S-nitrosylation. Selective detection of protein S-sulfhydryl modification has been addressed in mammalian systems by using a modification of the biotin switch technique [6] . By using this method, we have been able to identify 176 S-sulfhydrated proteins (FDR Arabidopsis thaliana ecotype Col-0. These proteins can be classified into fourteen groups based on the GO (Gene Ontology) classification, being the most abundant group the one containing proteins involved in electron transport and energy pathways such as tricarboxylic acid cycle or glycolysis. Several of the proteins identified in Arabidopsis have been also described in mammalian system such as actin, catalase, glutamine synthetase, glyceraldehyde 3 phosphate dehydrogenase, leucine aminopeptidase, ATP synthase, s-tubulin and UDP-glucose dehydrogenase [6] . The effect of sulfide on several enzyme activities is currently under investigation but preliminary data show that sulfide inhibits the enzymatic activity of the glutamine synthetase and this effect can be reverted by reducing agents such as DTT. On the contrary, glyceraldehyde 3 phosphate dehydrogenase increases its activity after sulfide treatment.