Nitric oxide and hydrogen sulfide share regulatory functions in higher plant events

Nitric oxide(NO)and hydrogen sulfide(HS)are two molecules that share signaling properties in plant and animal cells NO and H2S originate two farmilies of de rived mol ecules designated reactive nitrogen and sulfur species(RNS and RSS,respectively).These molecules are responsible for certain protein regulatory processes through posttranslational modifications(PTMs),being the most remarkable S nitrosation and persufidation,which afect the thiol group of cysteine residues.NO and H2S can also exert regulatory functions due to their interaction through the iron present in proteins that contain heme groups or iron-sulfur dlusters,as reported mainly in animal cells.Howewer,the available information in plant cells is still very limited thus far.In higher plants,NO and H2S are involved in a myriad of physiological events from seed germination to fruit ripening,but also the mec hanism of response to biotic and abiotic stress conditions.This vie wpoint manuscript highlights the functional regulatory parllelism of these two molecules which also interact with the metabolism of reactive oxygen species(ROS)in plant cells.

Hydrogen sulfide:A novel component in Arabidopsis peroxisomes which triggers catalase inhibition

Plant peroxisomes have the capacity to gen erate different reactive oxygen and nitrogen species(ROS and RNS),such as H2O2,superoxide radical(O2^·-),nitric oxide and peroxynitrite(ONOO^-).These organelles have an active nitrooxidative metabolism which can be exacerbated by adverse stress conditions.Hydrogen sulfide(H2S)is a new signaling gasotransmitter which can mediate the posttranslational modification(PTM)persulfidation.We used Arabidopsis thaliana transgenic seedlings expressing cyan fluorescent protein(CFP)fused to a canonical peroxisome targeting signal 1(PTS1)to visualize peroxisomes in living cells,as well as a specific fluorescent probe which showed that peroxisomes contain H2S.H2S was also detected in chloroplasts under glyphosate-induced oxidative stress conditions.Peroxisomal enzyme activities,including catalase,photorespiratory H2O2-generating glycolate oxidase(GOX)and hydroxypyruvate reductase(HPR),were assayed in vitro with a H2S donor.In line with the persulfidation of this enzyme,catalase activity declined significantly in the presence of the H2S donor.To corroborate the inhibitory effect of H2S on catalase activity,we also assayed pure catalase from bovine liver and pepper fruit-enriched samples,in which catalase activity was inhibited.Taken together,these data provide evidenee of the presence of H2S in plant peroxisomes which appears to regulate catalase activity and,consequently,the peroxisomal H2O2 metabolism.

Plant peroxisomes at the crossroad of NO and H2O2 metabolism

Plant peroxisomes are subcellular compartments involved in many biochemical pathways during the life cycle of a plant but also in the mechanism of response against adverse environmental conditions.These organelles have an active nitro-oxidative metabolism under physiological conditions but this could be exacerbated under stress situations.Furthermore,peroxisomes have the capacity to proliferateand also undergo biochemical adaptations depending on the surrounding cellular status.An important characteristic of peroxisomes is that they have a dynamic metabolism of reactive nitrogen and oxygen species(RNS and ROS)which generates two key molecules,nitric oxide(NO)and hydrogen peroxide(H2O2).These molecules can exert signaling functions by means of post-translational modifications that affect the functionality of target molecules like proteins,peptides or fatty acids.This review provides an overview of the endogenous metabolism of ROS and RNS in peroxisomes with special emphasis on polyamine and uric acid metabolism as well as the possibility that these organelles could be a source of signal molecules involved in the functional interconnection with other subcellular compartments.