L-Cysteine Desulfhydrase 1 Modulates the Generation of the Signaling Molecule Sulfide

Post-print of: Plant Signaling & Behavior 8:5, e24007; May 2013

L-Cysteine Desulfhydrase 1 modulates the generation of the signaling molecule sulfide in plant cytosol

Luis C. Romero, Irene García, Cecilia Gotor*

Instituto de Bioquímica Vegetal y Fotosíntesis; Consejo Superior de Investigaciones Científicas and Universidad de Sevilla; Sevilla, Spain

Keywords: Arabidopsis, autophagy, cysteine, cytosolic sulfide, transcriptional profile

*Correspondence to: Cecilia Gotor; E-mail:

Addendum to: Álvarez C, et al.Plant Cell 2012; 24:4621-4634; PMID: 23144183;

ABSTRACT

Consistent with data in animal systems,experimental evidence highlights sulfide as a signaling molecule of equal importanceto NO and H2O2in plant systems. In mammals,two cytosolic enzymes, cystathionine-synthase (CBS) and cystathionine -lyase (CSE), have been shown to be responsible for the endogenous production of sulfide. L-cysteine desulfhydrase 1 (DES1) has been recently established as the only enzyme that is involved in the generation of hydrogen sulfide in plant cytosol. Although plants have an available source of sulfide within chloroplasts, the basic stromal pH preventssulfide release into the cytosol. Therefore, DES1 is essential for the production of sulfide for signaling purposes.

For a long time, sulfide has been known primarily as a toxic molecule that is hazardous to the environment.Recently,however, sulfide has beenrecognized as agasotransmitter(gaseous molecule that transmits information between cells) of equal importanceto CO or NO in animal systems. Numerous reports describing the biological effects of sulfide highlight its physiological importance, and there is no doubt that most cells in mammals are able to produce and metabolize sulfidein a precise, regulated manner 1. However, identifyingthe molecular targets of sulfide and deciphering its mechanism of action remain challenging.A small number of direct targets, including ion channels, glyceraldehyde phosphate dehydrogenase (GAPDH), actin, tubulin, complex IV of the mitochondrial electron transport chain, and tyrosine phosphatase PTP1B, have been identified so far. In these cases, sulfhydration of reactive cysteines has been observed 2. Therefore, the sulfhydration can be considered a physiologic posttranslational modification for proteins, and previous studies have indicated that this modification can be regulated by competition between the nitrosylation and sulfhydration of the same cysteine residues. This competitionhas been observedon GAPDH protein3.

In recent years, experimental evidence emerging from numerous plant biology studies has shown H2Sto be asignaling molecule of equal importance to NO and H2O2. Sulfide has been shown to be involved in protection against copper, aluminum and boron stress 4-7,in the improvement of drought resistance, and in the promotionof heat and salinity tolerance 8-10. Furthermore, sulfidehas been suggested to play a rolein regulating photosynthesisand flower senescence and in prolonging the postharvest shelf life of fruits11-13. This molecule has also been identified as a component of the ABA signaling pathway in guard cells 14,15.

Our recent research has demonstrated that sulfide per se,but not sulfide as sulfur nutrient,exerts a general effect on autophagy through negative regulation16. Thus, it seems that independently of the sulfur nutrition status of the plant, in this case Arabidopsis thaliana, sulfide that is specifically generated inside the cytosol and that results from the degradation of cysteine acts as a signaling molecule and regulates the process of autophagy 17. Another interesting observationthat warrants further investigation is that sulfide seems to behave as a modulator of the transcriptional profile of the plant at its mature developmental stage. This hypothesis was proposed because when the capacity of the cytosol to release sulfide is reduced,the plant transcriptome is dramatically altered. This situation can be reversedby restoring the plant’s capacity togenerate sulfide (GSE32566).

It has recently been established that the main sources of endogenous production of H2S in mammalsare the enzymatic reactions catalyzed by cystathionine -synthase (CBS) and cystathionine -lyase (CSE)1,18.Both enzymes are known for their participationin the transsulfuration pathway,which is critical for the synthesis of cysteine from methionine (the latterbeing the source of sulfur from diet in animals). The two enzymes havealso been demonstrated to be the main proteinsthat are responsible for generating hydrogen sulfide from cysteine (Fig. 1). Both CBS and CSE use pyridoxal 5’-phosphate (PLP) as a cofactor and are exclusively located in the cytosol.We recently identifiedan analogousPLP-dependent enzyme with L-cysteine desulfhydrase activity,DES1,located in the cytosol in Arabidopsis thaliana plants16,19. DES1 is the only enzyme unequivocally established to be involved in the degradation of cysteine and the concomitant generation of hydrogen sulfide in the cytosol (Fig. 1).We have reached the conclusion that DES1 in the plant cell could be responsible for modulating the generation of sulfide for signaling in important processes, such as the progression of autophagy17.Doubtregarding this role could arise from the fact that in plants, the chloroplast is the main source of sulfide,which results from sulfate reduction in the sulfur assimilation pathway 20.This chloroplastic sulfide is thought to overflow into the cytosol. However,hydrogen sulfide is weakly acidic and dissociates in aqueous solutioninto H+ and SH-. This ionized form cannot permeate membranes 21. Thus, at the pH of 8.5 maintained by the chloroplast stroma under illumination,sulfide is mainly present in its charged form and is therefore unable to transport across the chloroplast envelope.

In conclusion, we suggest that DES1 modulates the production of sulfide in the plant cytosol and that this sulfide is utilized by the plant for signaling purposes. This hypothesis yields many areas of potential investigation, such as the mechanism underlying this modulation, the specific function of DES1 inthe signaling and control of different plant processes, the subcellular/tissue localization and regulation of the enzyme, and the mode of action forand specific targets of the DES1-generated sulfide. Our present investigation is committed toanswering some of these important questions.

Disclosure of Potential Conflicts of Interest

No potential conflicts of interest weredisclosed.

Acknowledgments

We would like to thank the European Regional Development Fund, the Ministerio de Economía y Competitividad of Spain (grant no. BIO2010-15201 and CSD2007–00057) and Junta de Andalucía of Spain (grant no. CVI-7190) for their financial support.

References

1.Wang R. Physiological implications of hydrogen sulfide: a whiff exploration that blossomed. Physiol Rev 2012; 92:791-896;PMID: 22535897; physrev.00017.2011.

2.Finkel T. From sulfenylation to sulfhydration: what a thiolate needs to tolerate. Sci Signal2012; 5: pe10; PMID: 22416275;

3Mustafa AK, Gadalla MM, Sen N, Kim S, Mu W, Gazi SK, Barrow RK, Yang G, Wang R, Snyder SH.H2S signals through protein S-sulfhydration. Sci Signal 2009; 2: ra72; PMID: 19903941;

4Zhang H, Hu LY, Hu KD, He YD, Wang SH, Luo JP. Hydrogen sulfide promotes wheat seed germination and alleviates oxidative damage against copper stress. J Integr Plant Biol 2008; 50: 1518-1529; PMID: 19093970; 00769.x.

5Zhang H, Tan ZQ, Hu LY, Wang SH, Luo JP, Jones RL. Hydrogen sulfide alleviates aluminum toxicity in germinating wheat seedlings. J Integr Plant Biol 2010; 52:556-567;PMID: 20590986;

6Wang BL, Shi L, Li YX,Zhang WH. Boron toxicity is alleviated by hydrogen sulfide in cucumber (Cucumis sativus L.) seedlings. Planta 2010; 231:1301-1309; PMID: 20224946;

7Dawood M, Cao F, Jahangir MM, Zhang G, Wu F. Alleviation of aluminum toxicity by hydrogen sulfide is related to elevated ATPase, and suppressed aluminum uptake and oxidative stress in barley. J Hazard Mater 2012; 209-210:121-128;PMID: 22281027;

8Jin Z, Shen J, Qiao Z, Yang G, Wang R, Pei Y. Hydrogen sulfide improves drought resistance in Arabidopsis thaliana. Biochem Biophys Res Commun2011; 414:481-486; PMID: 21986537;

9Li ZG, Gong M, Xie H, Yang L, Li J. Hydrogen sulfide donor sodium hydrosulfide-induced heat tolerance in tobacco (Nicotiana tabacum L) suspension cultured cells and involvement of Ca(2+) and calmodulin. Plant Sci 2012; 185-186:185-189;PMID: 22325880;

10Wang Y, Li L, Cui W, Xu S, Shen W, Wang R. Hydrogen sulfide enhances alfalfa (Medicago sativa) tolerance against salinity during seed germination by nitric oxide pathway. Plant Soil 2012; 351:107-119; 10.1007/s11104-011-0936-2.

11Chen J, Wu FH, Wang WH, Zheng CJ, Lin GH, Dong XJ, He JX, Pei ZM, Zheng HL. Hydrogen sulphide enhances photosynthesis through promoting chloroplast biogenesis, photosynthetic enzyme expression, and thiol redox modification in Spinacia oleracea seedlings. J Exp Bot 2011; 62:4481-4493; PMID: 21624977;

12Hu LY, Hu SL, Wu J, Li YH, Zheng JL, Wei ZJ, Liu J, Wang HL, Liu YS, Zhang H.Hydrogen sulfide prolongs postharvest shelf life of strawberry and plays an antioxidative role in fruits. J Agr Food Chem 2012; 60:8684-8693;PMID: 22871304; 10.1021/jf300728h.

13Zhang H, Hu S-L, Zhang Z-J, Hu L-Y, Jiang C-X, Wei Z-J, Liu J, Wang H-L, Jiang S-T. Hydrogen sulfide acts as a regulator of flower senescence in plants. Postharvest BiolTec 2011; 60:251-257;

14Garcia-Mata C, Lamattina L. Hydrogen sulphide, a novel gasotransmitter involved in guard cell signalling. New Phytol 2010; 188:977-984;PMID: 20831717;

15Lisjak M, Srivastava N, Teklic T, Civale L, Lewandowski K, Wilson I, Wood ME, Whiteman M, Hancock JT. A novel hydrogen sulfide donor causes stomatal opening and reduces nitric oxide accumulation. Plant Physiol Biochem 2010; 48:931-935;PMID: 20970349;

16Álvarez C, García I, Moreno I, Pérez-Pérez ME, Crespo JL, Romero LC, Gotor C. Cysteine-generated sulfide in the cytosol negatively regulates autophagy and modulates the transcriptional profile in Arabidopsis. Plant Cell 2012; 24:4621-4634; PMID: 23144183;

17Gotor C, García I, Crespo JL, Romero LC. Sulfide as a signaling molecule in autophagy. Autophagy 2013; 9; PMID: 23328265;

18Gadalla MM, Snyder SH. Hydrogen sulfide as a gasotransmitter. J Neurochem 2010; 113:14-26;PMID: 20067586;

19Álvarez, C, Calo L, Romero LC, García, I, Gotor C. An O-acetylserine(thiol)lyase homolog with L-cysteine desulfhydrase activity regulates cysteine homeostasis in Arabidopsis. Plant Physiol 2010; 152:656-669;PMID: 19955263;

20Takahashi H, Kopriva S, Giordano M, Saito K, Hell R. Sulfur assimilation in photosynthetic organisms: molecular functions and regulations of transporters and assimilatory enzymes. AnnuRev Plant Biol 2011; 62:157-184;PMID: 21370978;

21Kabil O, Banerjee R. Redox biochemistry of hydrogen sulfide. J Biol Chem 2010; 285:21903-21907; PMID: 20448039;

Legend to Figure

Figure 1. Enzymatic generation of sulfide from cysteine.Cystathionine-synthase (CBS) and cystathionine -lyase (CSE) catalyze this process in mammals; in plants, L-cysteine desulfhydrase 1 (DES1) performs thisfunction.

Figure 1