Hydrogen sulfide action in the regulation of plant autophagy

New role for thioredoxins in plants: Implication of TRXo1 in protein depersulfidation

Persulfidation, a posttranslational modification of cysteines to persulfides, is the best characterized molecular mechanism of H2S signaling. This study is focused on new functions for thioredoxins (TRXs) in plants beyond those of thiol disulfide (S-S) exchange, including the regulation of protein persulfidation as it has been described in animal systems. To elucidate the impact of TRXo1 deficiency on the protein persulfidation pattern in plants of Arabidopsis thaliana L. wild type (WT) and two Attrxo1 T-DNA insertion mutants grown under non stress conditions, a quantitative proteomic approach was performed. The proteomic analysis revealed a higher number of proteins that were more persulfidated in the mutants compared to WT plants, suggesting a role for TRXo1 in protein depersulfidation. Interestingly, most of the differentially persulfidated proteins were located in the chloroplast, implying a coordination between chloroplast H2S-dependent persulfidation and mitochondrial TRXo1 depersulfidation. Among the differentially persulfidated proteins located in mitochondria, the antioxidant enzymes sAPX, DHAR1 and MDAR6 were selected for further studies. The effect of H2S-dependent persulfidation on their enzymatic activities and its reversibility by the NADPH/thioredoxin reductase (NTRB)/TRXo1 system was analyzed, as well as their persulfidation levels were quantified. Sulfide treatment brought about increases in the activity levels of the enzymes, that match with a raise on the persulfidation levels. Interestingly, both activations declining after treatment with the thioredoxin system, indicate the regulation of their persulfidation by TRXo1. These results point to a positive effect of persulfidation on the enzymatic activities and also to a new depersulfidase activity for TRXo1. All together these results give a new insight of the mechanism of elimination of -SSH groups in plants exerted by TRXo1, and the involvement of a redox regulation on the protein persulfidation.

Regulation of Mitochondrial Respiration by Hydrogen Sulfide

Hydrogen sulfide (H2S), the third gasotransmitter, has positive roles in animals and plants. Mitochondria are the source and the target of H2S and the regulatory hub in metabolism, stress, and disease. Mitochondrial bioenergetics is a vital process that produces ATP and provides energy to support the physiological and biochemical processes. H2S regulates mitochondrial bioenergetic functions and mitochondrial oxidative phosphorylation. The article summarizes the recent knowledge of the chemical and biological characteristics, the mitochondrial biosynthesis of H2S, and the regulatory effects of H2S on the tricarboxylic acid cycle and the mitochondrial respiratory chain complexes. The roles of H2S on the tricarboxylic acid cycle and mitochondrial respiratory complexes in mammals have been widely studied. The biological function of H2S is now a hot topic in plants. Mitochondria are also vital organelles regulating plant processes. The regulation of H2S in plant mitochondrial functions is gaining more and more attention. This paper mainly summarizes the current knowledge on the regulatory effects of H2S on the tricarboxylic acid cycle (TCA) and the mitochondrial respiratory chain. A study of the roles of H2S in mitochondrial respiration in plants to elucidate the botanical function of H2S in plants would be highly desirable.

Sulfide promotes tolerance to drought through protein persulfidation in Arabidopsis

Hydrogen sulfide (H2S) is a signaling molecule that regulates essential plant processes. In this study, the role of H2S during drought was analysed, focusing on the underlying mechanism. Pretreatments with H2S before imposing drought on plants substantially improved the characteristic stressed phenotypes under drought and decreased the levels of typical biochemical stress markers such as anthocyanin, proline, and hydrogen peroxide. H2S also regulated drought-responsive genes and amino acid metabolism, and repressed drought-induced bulk autophagy and protein ubiquitination, demonstrating the protective effects of H2S pretreatment. Quantitative proteomic analysis identified 887 significantly different persulfidated proteins between control and drought stress plants. Bioinformatic analyses of the proteins more persulfidated in drought revealed that the most enriched biological processes were cellular response to oxidative stress and hydrogen peroxide catabolism. Protein degradation, abiotic stress responses, and the phenylpropanoid pathway were also highlighted, suggesting the importance of persulfidation in coping with drought-induced stress. Our findings emphasize the role of H2S as a promoter of enhanced tolerance to drought, enabling plants to respond more rapidly and efficiently. Furthermore, the main role of protein persulfidation in alleviating reactive oxygen species accumulation and balancing redox homeostasis under drought stress is highlighted.

Sustained Release of Hydrogen Sulfide from Di(t-butanol)dithiophosphate Phenethylamine Salt Encapsulated into Poly(lactic acid) Microparticles to Enhance the Growth of Radish Plants

The slow release of hydrogen sulfide has been shown to be beneficial to plants by protecting them from environmental stressors, increasing germination, and extending the lifetime of harvested fruits. A major challenge in this field is controlling the amount and location of release of hydrogen sulfide so that it is available for use by plants at optimal amounts. This article reports a dual method to release hydrogen sulfide near the roots of plants by controlling its release using the hydrolysis of a dithiophosphate and the degradation of poly(lactic acid) [PLA]. Di(t-butanol)dithiophosphate phenylethylamine (tBDPA) was dissolved in a solution of PLA, and the solvent was allowed to evaporate. The resulting solid was crushed in a blender and separated into microparticles with two different size distributions of 250-500 or 500-2000 μm. The microparticles were characterized by powder X-ray diffraction to measure the presence of microcrystals of tBDPA within PLA, and images obtained using scanning electron microscopy with energy dispersive X-ray analysis confirmed the presence of these crystals. Microparticles of tBDPA loaded within PLA were characterized for their release of phosphorus and hydrogen sulfide, which both showed a burst release within 3 days, followed by a steady release. Radish plants grown with microparticles of PLA loaded with tBDPA had up to a 141% increase in harvest yield compared to plants grown in the presence of free tBDPA not loaded into PLA, PLA microparticles without tBDPA, and control plants grown without PLA or tBDPA. These experiments showed that loading hydrogen sulfide-releasing chemicals into PLA is a promising method to improve the effect of hydrogen sulfide on plants.