Emission of Hydrogen Sulfide by Leaf Tissue in Response to l-Cysteine

Abstract

Leaf discs and detached leaves exposed to L-cysteine emitted a volatile sulfur compound which was proven by gas chromatography to be H2S. This phenomenon was demonstrated in all nine species tested (Cucumis sativus, Cucurbita pepo, Nicotiana tabacum, Coleus bbumei, Beta vulgaris, Phaseolus vulgaris, Medicago sativa, Hordeum vulgare, and Gossypium hirsutum). The emission of volatile sulfur by cucumber leaves occurred in the dark at a similar rate to that in the light. The emission of leaf discs reached the maximal rate, more than 40 picomoles per minute per square centimeter, 2 to 4 hours after starting exposure to L-cysteine; then it decreased. In the case of detached leaves, the maximum occurred 5 to 10 h after starting exposure. The average emission rate of H2S during the first 4 hours from leaf discs of cucurbits in response to 10 milimlar L-cysteine, was usually more than 40 picomoles per minute per square centimeter, i.e. 0.24 micromoles per hour per square decimeter. Leaf discs exposed to 1 milHimolar Lcysteine emitted only 2% as much as did the discs exposed to 10 millmolar L-cysteine. The emission from leaf discs and from detached leaves lasted for at least 5 and 15 hours, respectively. However, several hours after the maximal emission, injury of the leaves, manifested as chlorosis, was evdent.H2S emission was a specific consequence of exposure to L-cysteine; neither D-cysteine nor L-cystine elicited H2S emission. Aminooxyacetic acid, an inhibitor ofpyridoxal phosphate dependent enzymes, inhibited the emission.In a celi free system from cucumber leaves, H2S formation and its release occurred in response to L-cysteine. Feeding experiments with 135SIL_CyS_ teine showed that most of the sulfur in H2S was derived from sulfur in the L-cysteine supplied and that the H2S emitted for 9 hours accounted for 7 to 10% of L-cysteine taken up. 35S-labeled S032-and S042-were found in the tissue extract in addition to internal soluble S2-. These findigs suggest the existence of a sulfur cycle which converts L-cysteine to S042-through cysteine desulfhydration.Illuminated green leaves emit H2S when plants are exposed to s042- (32,35) or SO2 (6,27). Plants have the potential for reduction of s042-to a bound form of sulfide, which is incorporated into L-cysteine, by a light-driven assimilation pathway (1, 26). Therefore, the conversion of bound sulfide to free sulfide and its release as H2S is one possible origin of the H2S emitted in response to s042- (35 reductase (1,26). Still another possibility is that L-cysteine could be a precursor of H2S. L-Cysteine is a precursor ofmost organic sulfur compounds (9), and it regulates s042-uptake (13,16,29,30) Salmonella, L-cysteine is degraded to pyruvate, NH4' and sulfide by L-cysteine desulfhydrase, which is induced by L-cysteine (4,5,14,15). L-cysteine desulfhydrase activity has also been reported to exist in the XD strain of cultured tobacco cells and to be induced by L-cysteine in these cells (12). The H2S could also arise by cyanide-dependent desulfhydration of L-cyste...

GYY4137, a Novel Water-Soluble, H2S-Releasing Molecule

“…Interestingly, H 2 S production in plant tissues is likely derived from the sulfur assimilation pathways and L-cysteine desulfydrase (Ravilious & Jez, 2012;Romero et al, 2014;Takahashi, Kopriva, Giordano, Saito, & Hell, 2011). It is known that in the presence of high concentrations of sulfate (SO 4 2À ), sulfur dioxide (SO 2 ) and/or L-cysteine, plant tissues can synthesize, and emit H 2 S (Hällgren & Fredriksson, 1982;Sekiya, Schmidt, Wilson, & Filner, 1982;Wilson, Bressan, & Filner, 1978). Surprisingly, it was not until recently that a potential physiological role for H 2 S in plants was considered.…”

Role of O-Acetylserine in Hydrogen Sulfide Emission from Pumpkin Leaves in Response to Sulfate

“…Thus, desulfhydration of L-cysteine (pathway 2) or diversion from carrier-SH (pathway 1) seems to be the path of H2S biosynthesis in response to sulfate. The present experiments were performed to get information about which of these two possible pathways is responsible for the generation of H2S in leaf tissue supplied with excess sulfate.Leaf tissues of higher plants emit H2S into the atmosphere, when they are supplied with excess sulfate (6,13,14,16,24, 26), sulfite,17, 26),14,15,18). The path of H2S biosynthesis is different for each of these sulfur sources.…”

“…Leaf tissues of higher plants emit H2S into the atmosphere, when they are supplied with excess sulfate (6,13,14,16,24, 26), sulfite,17, 26),14,15,18). The path of H2S biosynthesis is different for each of these sulfur sources.…”

“…In response to sulfite or SO2, direct light-dependent reduction, probably catalyzed by a sulfite reductase, leads to emission of H2S (6, 17), although high amounts of bisulfite are oxidized to sulfate (12,17). In response to L-cysteine, H2S emission is caused by desulfhydration of L-cysteine, probably to pyruvate, ammonium, and SH-, catalyzed by a cysteine desulfhydrase (9,14,18). The path of H2S biosynthesis from sulfate, however, is much less certain.…”

“…Experiments on H2S emission in response to L-cysteine (15,18) The frozen samples were extracted twice with 5 ml 10 mM Nethylmaleimide in 80% ethanol in water (v/v). The residue was extracted twice with 5 ml distilled H20 at 100°C for 10 min.3S-Compounds in the combined ethanol and water extracts were separated by TLC as described previously (13,18).…”