S-nitrosated proteomic analysis reveals the regulatory roles of protein S-nitrosation and S-nitrosoglutathione reductase during Al-induced PCD in peanut root tips

Role of protein S-nitrosylation in plant growth and development

In plants, nitric oxide (NO) has been widely accepted as a signaling molecule that plays a role in different processes. Among the most relevant pathways by which NO and its derivatives realize their biological functions, post-translational protein modifications are worth mentioning. Protein S-nitrosylation has been the most studied NO-dependent regulatory mechanism; it is emerging as an essential mechanism for transducing NO bioactivity in plants and animals. In recent years, the research of protein S-nitrosylation in plant growth and development has made significant progress, including processes such as seed germination, root development, photosynthetic regulation, flowering regulation, apoptosis, and plant senescence. In this review, we focus on the current state of knowledge on the role of S-nitrosylation in plant growth and development and provide a better understanding of its action mechanisms.

Nitric oxide alleviates programmed cell death induced by cadmium in Solanum lycopersicum seedlings through protein S-nitrosylation

Cadmium (Cd), as a non-essential and toxic heavy metal in plants, has deleterious effects on plant physiological and biochemical processes. Nitric oxide (NO) is one of the most important signaling molecules for plants to response diverse stresses. Here, we found that Cd-induced programmed cell death (PCD) was accompanied by NO bursts, which exacerbated cell death when NO was removed and vice versa. Proteomic analysis of S-nitrosylated proteins showed that the differential proteins in Cd-induced PCD and in NO-alleviated PCD mainly exist together in carbohydrate metabolism and amino acid metabolism, while some of the differential proteins exist alone in metabolism of cofactors and vitamins and lipid metabolism. Meanwhile, S-nitrosylation of proteins in porphyrin and chlorophyll metabolism and starch and sucrose metabolism could explain the leaf chlorosis induced by PCD. Moreover, protein transport protein SEC23, ubiquitinyl hydrolase 1 and pathogenesis-related protein 1 were identified to be S-nitrosylated in vivo, and their expressions were increased in Cd-induced PCD while decreased in NO treatment. Similar results were obtained in tomato seedlings with higher S-nitrosylation. Taken together, our results indicate that NO might be involved in the regulation of Cd-induced PCD through protein S-nitrosylation, especially proteins involved in PCD response.

How plants respond to heavy metal contamination: a narrative review of proteomic studies and phytoremediation applications

MAIN CONCLUSION

Heavy metal pollution caused by human activities is a serious threat to the environment and human health. Plants have evolved sophisticated defence systems to deal with heavy metal stress, with proteins and enzymes serving as critical intercepting agents for heavy metal toxicity reduction. Proteomics continues to be effective in identifying markers associated with stress response and metabolic processes. This review explores the complex interactions between heavy metal pollution and plant physiology, with an emphasis on proteomic and biotechnological perspectives. Over the last century, accelerated industrialization, agriculture activities, energy production, and urbanization have established a constant need for natural resources, resulting in environmental degradation. The widespread buildup of heavy metals in ecosystems as a result of human activity is especially concerning. Although some heavy metals are required by organisms in trace amounts, high concentrations pose serious risks to the ecosystem and human health. As immobile organisms, plants are directly exposed to heavy metal contamination, prompting the development of robust defence mechanisms. Proteomics has been used to understand how plants react to heavy metal stress. The development of proteomic techniques offers promising opportunities to improve plant tolerance to toxicity from heavy metals. Additionally, there is substantial scope for phytoremediation, a sustainable method that uses plants to extract, sequester, or eliminate contaminants in the context of changes in protein expression and total protein behaviour. Changes in proteins and enzymatic activities have been highlighted to illuminate the complex effects of heavy metal pollution on plant metabolism, and how proteomic research has revealed the plant's ability to mitigate heavy metal toxicity by intercepting vital nutrients, organic substances, and/or microorganisms.

NO Is Not the Same as GSNO in the Regulation of Fe Deficiency Responses by Dicot Plants

Iron (Fe) is abundant in soils but with a poor availability for plants, especially in calcareous soils. To favor its acquisition, plants develop morphological and physiological responses, mainly in their roots, known as Fe deficiency responses. In dicot plants, the regulation of these responses is not totally known, but some hormones and signaling molecules, such as auxin, ethylene, glutathione (GSH), nitric oxide (NO) and S-nitrosoglutathione (GSNO), have been involved in their activation. Most of these substances, including auxin, ethylene, GSH and NO, increase their production in Fe-deficient roots while GSNO, derived from GSH and NO, decreases its content. This paradoxical result could be explained with the increased expression and activity in Fe-deficient roots of the GSNO reductase (GSNOR) enzyme, which decomposes GSNO to oxidized glutathione (GSSG) and NH3. The fact that NO content increases while GSNO decreases in Fe-deficient roots suggests that NO and GSNO do not play the same role in the regulation of Fe deficiency responses. This review is an update of the results supporting a role for NO, GSNO and GSNOR in the regulation of Fe deficiency responses. The possible roles of NO and GSNO are discussed by taking into account their mode of action through post-translational modifications, such as S-nitrosylation, and through their interactions with the hormones auxin and ethylene, directly related to the activation of morphological and physiological responses to Fe deficiency in dicot plants.

H2 O2 , NO, and H2 S networks during root development and signalling under physiological and challenging environments: Beneficial or toxic?

Hydrogen peroxide (H₂ O₂ ) is a reactive oxygen species (ROS) and a key modulator of the development and architecture of the root system under physiological and adverse environmental conditions. Nitric oxide (NO) and hydrogen sulphide (H₂ S) also exert myriad functions on plant development and signalling. Accumulating pieces of evidence show that depending upon the dose and mode of applications, NO and H₂ S can have synergistic or antagonistic actions in mediating H₂ O₂ signalling during root development. Thus, H₂ O₂ -NO-H₂ S crosstalk might essentially impart tolerance to elude oxidative stress in roots. Growth and proliferation of root apex involve crucial orchestration of NO and H₂ S-mediated ROS signalling which also comprise other components including mitogen-activated protein kinase, cyclins, cyclin-dependent kinases, respiratory burst oxidase homolog (RBOH), and Ca²⁺ flux. This assessment provides a comprehensive update on the cooperative roles of NO and H₂ S in modulating H₂ O₂ homoeostasis during root development, abiotic stress tolerance, and root-microbe interaction. Furthermore, it also analyses the scopes of some fascinating future investigations associated with strigolactone and karrikins concerning H₂ O₂ -NO-H₂ S crosstalk in plant roots.

Nitric oxide alleviates salt stress through protein S-nitrosylation and transcriptional regulation in tomato seedlings

NO enhances the resistance of tomato seedlings to salt stress through protein S-nitrosylation and transcriptional regulation, which involves the regulation of MAPK signaling and carbohydrate metabolism. Nitric oxide (NO) regulates various physiological and biochemical processes and stress responses in plants. We found that S-nitrosoglutathione (GSNO) treatment significantly promoted the growth of tomato seedling under NaCl stress, indicating that NO plays a positive role in salt stress resistance. Moreover, GSNO pretreatment resulted in an increase of endogenous NO level, S-nitrosothiol (SNO) content, S-nitrosoglutathione reductase (GSNOR) activity and GSNOR expression under salt stress, implicating that S-nitrosylation might be involved in NO-alleviating salt stress. To further explore whether S-nitrosylation is a key molecular mechanism of NO-alleviating salt stress, the biotin-switch technique and liquid chromatography/mass spectrometry/mass spectrometry (LC-MS/MS) were conducted. A total of 1054 putative S-nitrosylated proteins have been identified, which were mainly enriched in chloroplast, cytoplasm and mitochondrion. Among them, 15 and 22 S-nitrosylated proteins were involved in mitogen-activated protein kinase (MAPK) signal transduction and carbohydrate metabolism, respectively. In MAPK signaling, various S-nitrosylated proteins, SAM1, SAM3, SAM, PP2C and SnRK, were down-regulated and MAPK, MAPKK and MAPKK5 were up-regulated at the transcriptional level by GSNO treatment under salt stress compared to NaCl treatment alone. The GSNO pretreatment could reduce ethylene production and ABA content under NaCl stress. In addition, the activities of enzyme identified in carbohydrate metabolism, their expression at the transcriptional level and the metabolite content were up-regulated by GSNO supplication under salt stress, resulting in the activation of glycolysis and tricarboxylic acid cycle (TCA) cycles. Thus, these results demonstrated that NO might beneficially regulate MAPK signaling at transcriptional levels and activate carbohydrate metabolism at the post-translational and transcriptional level, protecting seedlings from energy deficiency and salinity, thereby alleviating salt stress-induced damage in tomato seedlings. It provides initial insights into the regulatory mechanisms of NO in response to salt stress.

Thiol-based Oxidative Posttranslational Modifications (OxiPTMs) of Plant Proteins

The thiol group of cysteine (Cys) residues, often present in the active center of the protein, is of particular importance to protein function, which is significantly determined by the redox state of a protein's environment. Our knowledge of different thiol-based oxidative posttranslational modifications (oxiPTMs), which compete for specific protein thiol groups, has increased over the last 10 years. The principal oxiPTMs include S-sulfenylation, S-glutathionylation, S-nitrosation, persulfidation, S-cyanylation and S-acylation. The role of each oxiPTM depends on the redox cellular state, which in turn depends on cellular homeostasis under either optimal or stressful conditions. Under such conditions, the metabolism of molecules such as glutathione, NADPH (reduced nicotinamide adenine dinucleotide phosphate), nitric oxide, hydrogen sulfide and hydrogen peroxide can be altered, exacerbated and, consequently, outside the cell's control. This review provides a broad overview of these oxiPTMs under physiological and unfavorable conditions, which can regulate the function of target proteins.