Genome-wide identification and expression analysis of glutathione S-transferase gene family in tomato: Gaining an insight to their physiological and stress-specific roles

Overlooked and misunderstood: can glutathione conjugates be clues to understanding plant glutathione transferases?

Plant glutathione transferases (GSTs) constitute a large and diverse family of enzymes that are involved in plant stress response, metabolism and defence, yet their physiological functions remain largely elusive. Consistent with the traditional view on GSTs across organisms as detoxification enzymes, in vitro most plant GSTs catalyse glutathionylation, conjugation of the tripeptide glutathione (GSH; γ-Glu-Cys-Gly) onto reactive molecules. However, when it comes to elucidating GST functions, it remains a key challenge that the endogenous plant glutathione conjugates (GS-conjugates) that would result from such glutathionylation reactions are rarely reported. Furthermore, GSTs often display high substrate promiscuity, and their proposed substrates are prone to spontaneous chemical reactions with GSH; hence, single-gene knockouts rarely provide clear chemotypes or phenotypes. In a few cases, GS-conjugates are demonstrated to be biosynthetic intermediates that are rapidly further metabolized towards a pathway end product, explaining their low abundance and rare detection. In this review, we summarize the current knowledge of plant GST functions and how and possibly why evolution has resulted in a broad and extensive expansion of the plant GST family. Finally, we demonstrate that endogenous GS-conjugates are more prevalent in plants than assumed and suggest they are overlooked as clues towards the identification of plant GST functions. This article is part of the theme issue 'The evolution of plant metabolism'.

An intronless tau class glutathione transferase detoxifies several herbicides in flufenacet-resistant ryegrass

Resistance to preemergence herbicides, e.g. inhibitors of the biosynthesis of very-long-chain fatty acids (VLCFAs), is evolving in response to increased use of these compounds. Grass weeds such as ryegrasses (Lolium spp.) have accumulated resistance to various herbicide modes of action. Here, an RNA-seq analysis was conducted using 3 ryegrass populations resistant to the VLCFA biosynthesis inhibitor flufenacet to investigate this phenomenon. Besides various transcripts, including putative long noncoding RNAs (lncRNAs), a single putatively functional tau class glutathione transferase (GST) was constitutively differentially expressed. It was further induced by herbicide application. This GST was expressed as a recombinant protein in Escherichia coli along with other GSTs and detoxified flufenacet rapidly in vitro. Detoxification rates of other herbicides tested in vitro were in accordance with cross-resistance patterns previously determined in vivo. A genome-wide GST analysis revealed that the candidate GST was located in a cluster of 3 intronless GSTs. Their intronless nature possibly results from the retroposition of cellular mRNAs followed by tandem duplication and may affect gene expression. The large number of GSTs (≥195) in the genome of rigid ryegrass (Lolium rigidum) compared with other plant organisms is likely a key factor in the ability of this weed to evolve resistance to different herbicide chemistries. However, in the case of flufenacet resistance, a single upregulated GST with high affinity for the substrate flufenacet possibly contributes overproportionally to rapid herbicide detoxification in planta. The regulation of this gene and the role of differentially expressed transcripts, including various putative lncRNAs, require further investigation.

Identification of the Novel Small Compound Stress Response Regulators 1 and 2 That Affect Plant Abiotic Stress Signaling

Abiotic stresses, such as drought, salinity, and extreme temperatures, limit plant growth and development, reducing crop yields. Therefore, a more comprehensive understanding of the signaling mechanisms and responses of plants to changing environmental conditions is crucial for improving sustainable agricultural productivity. Chemical screening was conducted to find novel small compounds that act as regulators of the abiotic stress signaling pathway using the ABA-inducible transgenic reporter line. Small molecules called stress response regulators (SRRs) were isolated by screening a synthetic library composed of 14,400 small compounds, affecting phenotypes such as seed germination, root growth, and gene expression in response to multiple abiotic stresses. Seeds pretreated with SRR compounds positively affected the germination rate and radicle emergence of Arabidopsis and tomato plants under abiotic stress conditions. The SRR-priming treatment enhanced the transcriptional responses of abiotic stress-responsive genes in response to subsequent salt stress. The isolation of the novel molecules SRR1 and SRR2 will provide a tool to elucidate the complex molecular networks underlying the plant stress-tolerant responses.

Expression pattern of the poplar GSTU family members in response to Alternaria alternate and PdbGSTU10 confers A. alternate resistance to Populus davidiana × P. bolleana

Plant tau glutathione S-transferase (GSTU) is a kind of multiple functions enzyme, but its specific roles in poplar disease resistance remain uncertain. In this study, 27 PdbGSTU-encoding genes from Populus davidiana × P. bollena were cloned and their protein architectures and phylogenetic relationships were subsequently analyzed. Expression analysis revealed that PdbGSTUs were differentially expressed under Alternaria alternate infection. Then, the PdbGSTU10 was further induced by phytohormones and H2O2, especially salicylic acid (SA), indicating its potential role in the pathogen defense of poplar. Subsequently, gain- and loss-of-function assays showed that overexpressed PdbGSTU10 activated antioxidant enzymes and significantly decreased reactive oxygen species (ROS) content, ultimately improving the resistance to A. alternate in poplar. Conversely, silencing PdbGSTU10 had the opposite effect. Moreover, overexpressed PdbGSTU10 also increased the content of SA and induced the expression of SA signal-related genes. These results showed that PdbGSTU10 may enhance disease resistance in poplar by scavenging ROS and affecting the SA signaling pathway. Our findings contribute to the understanding of the functions of GSTU in woody plants, particularly in disease resistance.

Genome-Wide Identification of Glutathione S-Transferase Family from Dendrobium officinale and the Functional Characterization of DoGST5 in Cadmium Tolerance

Glutathione S-transferases (GSTs) are members of a protein superfamily with diverse physiological functions, including cellular detoxification and protection against oxidative damage. However, there is limited research on GSTs responding to cadmium (Cd) stress. This study classified 46 GST genes in Dendrobium officinale (D. officinale) into nine groups using model construction and domain annotation. Evolutionary analysis revealed nine subfamilies with diverse physical and chemical properties. Prediction of subcellular localization revealed that half of the GST members were located in the cytoplasm. According to the expression analysis of GST family genes responding to Cd stress, DoGST5 responded significantly to Cd stress. Transient expression of DoGST5-GFP in tobacco leaves revealed that DoGST5 was localized in the cytoplasm. DoGST5 overexpression in Arabidopsis enhanced Cd tolerance by reducing Cd-induced H2O2 and O2- levels. These findings demonstrate that DoGST5 plays a critical role in enhancing Cd tolerance by balancing reactive oxygen species (ROS) levels, offering potential applications for improving plant adaptability to heavy metal stress.

Identification and Characterization of the Glutathione S-Transferase Gene Family in Blueberry (Vaccinium corymbosum) and Their Potential Roles in Anthocyanin Intracellular Transportation

The glutathione S-transferases (GSTs, EC 2.5.1.18) constitute a versatile enzyme family with pivotal roles in plant stress responses and detoxification processes. Recent discoveries attributed the additional function of facilitating anthocyanin intracellular transportation in plants to GSTs. Our study identified 178 VcGST genes from 12 distinct subfamilies in the blueberry genome. An uneven distribution was observed among these genes across blueberry's chromosomes. Members within the same subfamily displayed homogeneity in gene structure and conserved protein motifs, whereas marked divergence was noted among subfamilies. Functional annotations revealed that VcGSTs were significantly enriched in several gene ontology and KEGG pathway categories. Promoter regions of VcGST genes predominantly contain light-responsive, MYB-binding, and stress-responsive elements. The majority of VcGST genes are subject to purifying selection, with whole-genome duplication or segmental duplication serving as key processes that drive the expansion of the VcGST gene family. Notably, during the ripening of the blueberry fruit, 100 VcGST genes were highly expressed, and the expression patterns of 24 of these genes demonstrated a strong correlation with the dynamic content of fruit anthocyanins. Further analysis identified VcGSTF8, VcGSTF20, and VcGSTF22 as prime candidates of VcGST genes involved in the anthocyanin intracellular transport. This study provides a reference for the exploration of anthocyanin intracellular transport mechanisms and paves the way for investigating the spectrum of GST functions in blueberries.

Genome-Wide Identification of Glutathione S-Transferase Genes in Eggplant (Solanum melongena L.) Reveals Their Potential Role in Anthocyanin Accumulation on the Fruit Peel

Anthocyanins are ubiquitous pigments derived from the phenylpropanoid compound conferring red, purple and blue pigmentations to various organs of horticultural crops. The metabolism of flavonoids in the cytoplasm leads to the biosynthesis of anthocyanin, which is then conveyed to the vacuoles for storage by plant glutathione S-transferases (GST). Although GST is important for transporting anthocyanin in plants, its identification and characterization in eggplant (Solanum melongena L.) remains obscure. In this study, a total of 40 GST genes were obtained in the eggplant genome and classified into seven distinct chief groups based on the evolutionary relationship with Arabidopsis thaliana GST genes. The seven subgroups of eggplant GST genes (SmGST) comprise: dehydroascorbate reductase (DHAR), elongation factor 1Bγ (EF1Bγ), Zeta (Z), Theta(T), Phi(F), Tau(U) and tetra-chlorohydroquinone dehalogenase TCHQD. The 40 GST genes were unevenly distributed throughout the 10 eggplant chromosomes and were predominantly located in the cytoplasm. Structural gene analysis showed similarity in exons and introns within a GST subgroup. Six pairs of both tandem and segmental duplications have been identified, making them the primary factors contributing to the evolution of the SmGST. Light-related cis-regulatory elements were dominant, followed by stress-related and hormone-responsive elements. The syntenic analysis of orthologous genes indicated that eggplant, Arabidopsis and tomato (Solanum lycopersicum L.) counterpart genes seemed to be derived from a common ancestry. RNA-seq data analyses showed high expression of 13 SmGST genes with SmGSTF1 being glaringly upregulated on the peel of purple eggplant but showed no or low expression on eggplant varieties with green or white peel. Subsequently, SmGSTF1 had a strong positive correlation with anthocyanin content and with anthocyanin structural genes like SmUFGT (r = 0.9), SmANS (r = 0.85), SmF3H (r = 0.82) and SmCHI2 (r = 0.7). The suppression of SmGSTF1 through virus-induced gene silencing (VIGs) resulted in a decrease in anthocyanin on the infiltrated fruit surface. In a nutshell, results from this study established that SmGSTF1 has the potential of anthocyanin accumulation in eggplant peel and offers viable candidate genes for the improvement of purple eggplant. The comprehensive studies of the SmGST family genes provide the foundation for deciphering molecular investigations into the functional analysis of SmGST genes in eggplant.

DcGST1, encoding a glutathione S-transferase activated by DcMYB7, is the main contributor to anthocyanin pigmentation in purple carrot

The color of purple carrot taproots mainly depends on the anthocyanins sequestered in the vacuoles. Glutathione S-transferases (GSTs) are key enzymes involved in anthocyanin transport. However, the precise mechanism of anthocyanin transport from the cytosolic surface of the endoplasmic reticulum (ER) to the vacuoles in carrots remains unclear. In this study, we conducted a comprehensive analysis of the carrot genome, leading to the identification of a total of 41 DcGST genes. Among these, DcGST1 emerged as a prominent candidate, displaying a strong positive correlation with anthocyanin pigmentation in carrot taproots. It was highly expressed in the purple taproot tissues of purple carrot cultivars, while it was virtually inactive in the non-purple taproot tissues of purple and non-purple carrot cultivars. DcGST1, a homolog of Arabidopsis thaliana TRANSPARENT TESTA 19 (TT19), belongs to the GSTF clade and plays a crucial role in anthocyanin transport. Using the CRISPR/Cas9 system, we successfully knocked out DcGST1 in the solid purple carrot cultivar 'Deep Purple' ('DPP'), resulting in carrots with orange taproots. Additionally, DcMYB7, an anthocyanin activator, binds to the DcGST1 promoter, activating its expression. Compared with the expression DcMYB7 alone, co-expression of DcGST1 and DcMYB7 significantly increased anthocyanin accumulation in carrot calli. However, overexpression of DcGST1 in the two purple carrot cultivars did not change the anthocyanin accumulation pattern or significantly increase the anthocyanin content. These findings improve our understanding of anthocyanin transport mechanisms in plants, providing a molecular foundation for improving and enhancing carrot germplasm.

The role of salicylic acid on glutathione metabolism under endoplasmic reticulum stress in tomato

The endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) are highly dependent on phytohormones such as salicylic acid (SA). In this study, the effect of SA supplementation and the lack of endogenous SA on glutathione metabolism were investigated under ER stress in wild-type (WT) and transgenic SA-deficient NahG tomato (Solanum lycopersicum L.) plants. The expression of the UPR marker gene SlBiP was dependent on SA levels and remained lower in NahG plants. Exogenous application of the chemical chaperone 4-phenylbutyrate (PBA) also reduced tunicamycin (Tm)-induced SlBiP transcript accumulation. At the same time, Tm-induced superoxide and hydrogen peroxide production were independent of SA, whereas the accumulation of reduced form of glutathione (GSH) and the oxidised glutathione (GSSG) was regulated by SA. Tm increased the activity of glutathione reductase (GR; EC 1.6.4.2) independently of SA, but the activities of dehydroascorbate reductase (DHAR; EC 1.8.5.1) and glutathione S-transferases (GSTs; EC 2.5.1.18) were increased by Tm in a SA-dependent manner. SlGR2, SlGGT and SlGSTT2 expression was activated in a SA-dependent way upon Tm. Although expression of SlGSH1, SlGSTF2, SlGSTU5 and SlGTT3 did not change upon Tm treatment in leaves, SlGR1 and SlDHAR2 transcription decreased. PBA significantly increased the expression of SlGR1, SlGR2, SlGSTT2, and SlGSTT3, which contributed to the amelioration of Tm-induced ER stress based on the changes in lipid peroxidation and cell viability. Malondialdehyde accumulation and electrolyte leakage were significantly higher in WT as compared to NahG tomato leaves under ER stress, further confirming the key role of SA in this process.

Isolation and characterization of glutathione S-transferase genes and their transcripts in Saccharina japonica (Laminariales, Phaeophyceae) during development and under abiotic stress

BACKGROUND

Glutathione S-transferase (GST) is a crucial enzyme for metabolism, detoxification, and stress resistance in organisms. Many GSTs have been identified in seaweeds, but the isolation and functional analysis of GSTs in Saccharina japonica have not been completed.

RESULT

In this study, a total of 32 SjGST genes, localized on 10 scaffolds and 6 contigs, were identified and categorized into three groups. Most of these SjGSTs were presumed to be distributed in the cytoplasm. Tandem duplication had a significant influence on the expansion of the SjGST gene family. Functional analysis of cis-acting elements in the promoter regions demonstrated that SjGSTs enhance the stress resistance of the kelp. Quantitative real-time PCR tests confirmed that SjGSTs positively influence S. japonica sporophytes under stress from low salinity, drought, and high temperature. Recombinant yeast tests further affirmed the role of SjGSTs in stress resistance; SjGSTs improved the growth rate of recombinant yeast under 1.5 M NaCl or 8 mM H2O2. Analysis of biochemical parameters indicated that the optimum temperatures for SjGST20 and SjGST22 were 20 °C, and the optimum pH values were 7.0 and 8.0 for SjGST20 and SjGST22, respectively. The Km values for the substrate 1-chloro-2,4-dinitrobenzene (CDNB) were 2.706 mM and 0.674 mM and were 6.146 mM and 3.559 mM for the substrate glutathione (GSH) for SjGST20 and SjGST22, respectively.

CONCLUSION

SjGSTs are important stress resistant genes in S. japonica. This research results will enhance our understanding the function of GSTs in brown seaweeds, and explained its functional roles in stress resistance in marine environments.

Glutathione Transferases Are Involved in the Genotype-Specific Salt-Stress Response of Tomato Plants

Glutathione transferases (GSTs) are one of the most versatile multigenic enzyme superfamilies. In our experiments, the involvement of the genotype-specific induction of GST genes and glutathione- or redox-related genes in pathways regulating salt-stress tolerance was examined in tomato cultivars (Solanum lycopersicum Moneymaker, Mobil, and Elán F1). The growth of the Mobil plants was adversely affected during salt stress (100 mM of NaCl), which might be the result of lowered glutathione and ascorbate levels, a more positive glutathione redox potential (EGSH), and reduced glutathione reductase (GR) and GST activities. In contrast, the Moneymaker and Elán F1 cultivars were able to restore their growth and exhibited higher GR and inducible GST activities, as well as elevated, non-enzymatic antioxidant levels, indicating their enhanced salt tolerance. Furthermore, the expression patterns of GR, selected GST, and transcription factor genes differed significantly among the three cultivars, highlighting the distinct regulatory mechanisms of the tomato genotypes during salt stress. The correlations between EGSH and gene expression data revealed several robust, cultivar-specific associations, underscoring the complexity of the stress response mechanism in tomatoes. Our results support the cultivar-specific roles of distinct GST genes during the salt-stress response, which, along with WRKY3, WRKY72, DREB1, and DREB2, are important players in shaping the redox status and the development of a more efficient stress tolerance in tomatoes.

Genome-Wide Datasets of Chicories (Cichorium intybus L.) for Marker-Assisted Crop Breeding Applications: A Systematic Review and Meta-Analysis

Cichorium intybus L. is the most economically important species of its genus and among the most important of the Asteraceae family. In chicory, many linkage maps have been produced, several sets of mapped and unmapped markers have been developed, and dozens of genes linked to traits of agronomic interest have been investigated. This treasure trove of information, properly cataloged and organized, is of pivotal importance for the development of superior commercial products with valuable agronomic potential in terms of yield and quality, including reduced bitter taste and increased inulin production, as well as resistance or tolerance to pathogens and resilience to environmental stresses. For this reason, a systematic review was conducted based on the scientific literature published in chicory during 1980-2023. Based on the results obtained from the meta-analysis, we created two consensus maps capable of supporting marker-assisted breeding (MAB) and marker-assisted selection (MAS) programs. By taking advantage of the recently released genome of C. intybus, we built a 639 molecular marker-based consensus map collecting all the available mapped and unmapped SNP and SSR loci available for this species. In the following section, after summarizing and discussing all the genes investigated in chicory and related to traits of interest such as reproductive barriers, sesquiterpene lactone biosynthesis, inulin metabolism and stress response, we produced a second map encompassing 64 loci that could be useful for MAS purposes. With the advent of omics technologies, molecular data chaos (namely, the situation where the amount of molecular data is so complex and unmanageable that their use becomes challenging) is becoming far from a negligible issue. In this review, we have therefore tried to contribute by standardizing and organizing the molecular data produced thus far in chicory to facilitate the work of breeders.

Genome-wide identification and characterization of glutathione S-transferase gene family in quinoa (Chenopodium quinoa Willd.)

The present investigation was envisaged for large scale in-silico genome wide identification and characterization of glutathione S-transferases (GSTs) in Chenopodium quinoa. In this study, a total of 120 GST genes (CqGSTs) were identified and divided into 11 classes of which tau and phi were highest in numbers. The average protein length of protein was found to be 279.06 with their corresponding average molecular weight of 31,819.4 kDa. The subcellular localization analysis results showed that proteins were centrally localized in the cytoplasm followed by chloroplast, mitochondria and plastids. Structural analysis revealed the presence of 2 -14 exons in CqGST genes. Most of the proteins possessed two exon one intron organization. MEME analysis identified 15 significantly conserved motifs with a width of 6-50 amino acids. Motifs 1, 3, 2, 5, 6, 8, 9 and 13 were found specifically in tau class family; motifs 3, 4, 5, 6, 7 and 9 were found in phi class gene family, while motifs 3, 4, 13 and 14 were found in metaxin class. Multiple sequence alignment revealed highly conserved N-terminus with active site serine (Ser; S) or cysteine (Cys; C) residue for the activation of GSH binding and GST catalytic activity. The gene loci were found to be unevenly distributed across 18 different chromosomes with a maximum of 17 genes located on chromosome number 7. Dominance of alpha helix was followed by coil, extended strand and beta turns. Gene duplication analysis revealed that segmental duplication and purifying type selection were highest in number and found to be main source of expansion of GST gene family. Cis acting regulatory elements analysis showed the presence of 21 different elements involved in stress, hormone and light response and cellular development. The evolutionary relationship of CqGST proteins carried out using maximum likelihood method revealed that all the tau and phi class GSTs were closely associated with those of G. max, O. sativa and A. thaliana. Molecular docking of GST molecules with the fungicide metalaxyl showed that the CqGSTF1 had the lowest binding energy. The comprehensive study of CqGST gene family in quinoa provides groundwork for further functional analysis of CqGST genes in the species at molecular level and has potential applications in plant breeding.

Genome-wide identification and characterization of Glutathione S-Transferases (GSTs) and their expression profile under abiotic stresses in tobacco (Nicotiana tabacum L.)

BACKGROUND

Glutathione S-transferases (GSTs) are large and multifunctional proteases that play an important role in detoxification, protection against biotic and abiotic stresses, and secondary metabolite transportation which is essential for plant growth and development. However, there is limited research on the identification and function of NtGSTs.

RESULTS

This study uses K326 and other six tobacco varieties (Hongda, HG, GDH11, Va116, VG, and GDH88) as materials to conduct comprehensive genome-wide identification and functional characterization of the GST gene in tobacco. A total of 59 NtGSTs were identified and classified into seven subfamilies via the whole-genome sequence analysis, with the Tau type serving as the major subfamily. The NtGSTs in the same branch of the evolutionary tree had similar exon/intron structure and motif constitution. There were more than 42 collinear blocks between tobacco and pepper, tomato, and potato, indicating high homology conservation between them. Twelve segmental duplicated gene pairs and one tandem duplication may have had a substantial impact on the evolution and expansion of the tobacco GST gene family. The RT-qPCR results showed that the expression patterns of NtGSTs varied significantly among tissues, varieties, and multiple abiotic stresses, suggesting that NtGST genes may widely respond to various abiotic stresses and hormones in tobacco, including NtGSTF4, NtGSTL1, NtGSTZ1, and NtGSTU40.

CONCLUSIONS

This study provides a comprehensive analysis of the NtGST gene family, including structures and functions. Many NtGSTs play a critical regulatory role in tobacco growth and development, and responses to abiotic stresses. These findings offer novel and valuable insights for understanding the biological function of NtGSTs and the reference materials for cultivating highly resistant varieties and enhancing the yield and quality of crops.

Glutathione Contribution in Interactions between Turnip mosaic virus and Arabidopsis thaliana Mutants Lacking Respiratory Burst Oxidase Homologs D and F

Respiratory burst oxidase homologs (Rbohs) play crucial and diverse roles in plant tissue-mediated production of reactive oxygen species during the development, growth, and response of plants to abiotic and biotic stress. Many studies have demonstrated the contribution of RbohD and RbohF in stress signaling in pathogen response differentially modulating the immune response, but the potential role of the Rbohs-mediated response in plant-virus interactions remains unknown. The present study analyzed, for the first time, the metabolism of glutathione in rbohD-, rbohF-, and rbohD/F-transposon-knockout mutants in response to Turnip mosaic virus (TuMV) infection. rbohD-TuMV and Col-0-TuMV interactions were characterized by susceptible reaction to TuMV, associated with significant activity of GPXLs (glutathione peroxidase-like enzymes) and induction of lipid peroxidation in comparison to mock-inoculated plants, with reduced total cellular and apoplastic glutathione content observed at 7-14 dpi and dynamic induction of apoplast GSSG (oxidized glutathione) at 1-14 dpi. Systemic virus infection resulted in the induction of AtGSTU1 and AtGSTU24, which was highly correlated with significant downregulation of GSTs (glutathione transferases) and cellular and apoplastic GGT (γ-glutamyl transferase) with GR (glutathione reductase) activities. On the contrary, resistant rbohF-TuMV reactions, and especially enhanced rbohD/F-TuMV reactions, were characterized by a highly dynamic increase in total cellular and apoplastic glutathione content, with induction of relative expression of AtGGT1, AtGSTU13, and AtGSTU19 genes. Moreover, virus limitation was highly correlated with the upregulation of GSTs, as well as cellular and apoplastic GGT with GR activities. These findings clearly indicate that glutathione can act as a key signaling factor in not only susceptible rbohD reaction but also the resistance reaction presented by rbohF and rbohD/F mutants during TuMV interaction. Furthermore, by actively reducing the pool of glutathione in the apoplast, GGT and GR enzymes acted as a cell first line in the Arabidopsis-TuMV pathosystem response, protecting the cell from oxidative stress in resistant interactions. These dynamically changed signal transductions involved symplast and apoplast in mediated response to TuMV.

Tomato SlGSTU38 interacts with the PepMV coat protein and promotes viral infection

Pepino mosaic virus (PepMV) is pandemic in tomato crops, causing important economic losses world-wide. No PepMV-resistant varieties have been developed yet. Identification of host factors interacting with PepMV proteins is a promising source of genetic targets to develop PepMV-resistant varieties. The interaction between the PepMV coat protein (CP) and the tomato glutathione S-transferase (GST) SlGSTU38 was identified in a yeast two-hybrid (Y2H) screening and validated by directed Y2H and co-immunoprecipitation assays. SlGSTU38-knocked-out Micro-Tom plants (gstu38) generated by the CRISPR/Cas9 technology together with live-cell imaging were used to understand the role of SlGSTU38 during infection. The transcriptomes of healthy and PepMV-infected wild-type (WT) and gstu38 plants were profiled by RNA-seq analysis. SlGSTU38 functions as a PepMV-specific susceptibility factor in a cell-autonomous manner and relocalizes to the virus replication complexes during infection. Besides, knocking out SlGSTU38 triggers reactive oxygen species accumulation in leaves and the deregulation of stress-responsive genes. SlGSTU38 may play a dual role: On the one hand, SlGSTU38 may exert a proviral function depending on its specific interaction with the PepMV CP; and on the other hand, SlGSTU38 may delay PepMV-infection sensing by participating in the redox intracellular homeostasis in a nonspecific manner.

GmGSTU23 Encoding a Tau Class Glutathione S-Transferase Protein Enhances the Salt Tolerance of Soybean (Glycine max L.)

Salt stress has a detrimental impact on crop yield, quality, and profitability. The tau-like glutathione transferases (GSTs) represent a significant group of enzymes that play a crucial role in plant stress responses, including salt stress. In this study, we identified a tau-like glutathione transferase family gene from soybean named GmGSTU23. Expression pattern analysis revealed that GmGSTU23 was predominantly expressed in the roots and flowers and exhibited a concentration–time-specific pattern in response to salt stress. Transgenic lines were generated and subjected to phenotypic characterization under salt stress. The transgenic lines exhibited increased salt tolerance, root length, and fresh weight compared to the wild type. Antioxidant enzyme activity and malondialdehyde content were subsequently measured, and the data revealed no significant differences between the transgenic and wild-type plants in the absence of salt stress. However, under salt stress, the wild-type plants exhibited significantly lower activities of SOD, POD, and CAT than the three transgenic lines, whereas the activity of APX and the content of MDA showed the opposite trend. We identified changes in glutathione pools and associated enzyme activity to gain insights into the underlying mechanisms of the observed phenotypic differences. Notably, under salt stress, the transgenic Arabidopsis’s GST activity, GR activity, and GSH content were significantly higher than those of the wild type. In summary, our findings suggest that GmGSTU23 mediates the scavenging of reactive oxygen species and glutathione by enhancing the activity of glutathione transferase, thereby conferring enhanced tolerance to salt stress in plants.

Genome-Wide Identification and Expression Profiling of Glutathione S-Transferase Gene Family in Foxtail Millet (Setaria italica L.)

Glutathione S-transferases (GSTs) are a critical superfamily of multifunctional enzymes in plants. As a ligand or binding protein, GSTs regulate plant growth and development and detoxification. Foxtail millet (Setaria italica (L.) P. Beauv) could respond to abiotic stresses through a highly complex multi-gene regulatory network in which the GST family is also involved. However, GST genes have been scarcely studied in foxtail millet. Genome-wide identification and expression characteristics analysis of the foxtail millet GST gene family were conducted by biological information technology. The results showed that 73 GST genes (SiGSTs) were identified in the foxtail millet genome and were divided into seven classes. The chromosome localization results showed uneven distribution of GSTs on the seven chromosomes. There were 30 tandem duplication gene pairs belonging to 11 clusters. Only one pair of SiGSTU1 and SiGSTU23 were identified as fragment duplication genes. A total of ten conserved motifs were identified in the GST family of foxtail millet. The gene structure of SiGSTs is relatively conservative, but the number and length of exons of each gene are still different. The cis-acting elements in the promoter region of 73 SiGST genes showed that 94.5% of SiGST genes possessed defense and stress-responsive elements. The expression profiles of 37 SiGST genes covering 21 tissues suggested that most SiGST genes were expressed in multiple organs and were highly expressed in roots and leaves. By qPCR analysis, we found that 21 SiGST genes were responsive to abiotic stresses and abscisic acid (ABA). Taken together, this study provides a theoretical basis for identifying foxtail millet GST family information and improving their responses to different stresses.

Genome-wide in silico identification of glutathione S-transferase (GST) gene family members in fig (Ficus carica L.) and expression characteristics during fruit color development

Glutathione S-transferase (GSTs), a large and diverse group of multi-functional enzymes (EC 2.5.1.18), are associated with cellular detoxification, various biotic and abiotic stress responses, as well as secondary metabolites transportation. Here, 53 members of the FcGST gene family were screened from the genome database of fig (Ficus carica), which were further classified into five subfamilies, and the tau and phi were the major subfamilies. These genes were unevenly distributed over all the 13 chromosomes, and 12 tandem and one segmental duplication may contribute to this family expansion. Syntenic analysis revealed that FcGST shared closer genetic evolutionary origin relationship with species from the Ficus genus of the Moraceae family, such as F. microcarpa and F. hispida. The FcGST members of the same subfamily shared similar gene structure and motif distribution. The α helices were the chief structure element in predicted secondary and tertiary structure of FcGSTs proteins. GO and KEGG indicated that FcGSTs play multiple roles in glutathione metabolism and stress reactions as well as flavonoid metabolism. Predictive promoter analysis indicated that FcGSTs gene may be responsive to light, hormone, stress stimulation, development signaling, and regulated by MYB or WRKY. RNA-seq analysis showed that several FcGSTs that mainly expressed in the female flower tissue and peel during 'Purple-Peel' fig fruit development. Compared with 'Green Peel', FcGSTF1, and FcGSTU5/6/7 exhibited high expression abundance in the mature fruit purple peel. Additionally, results of phylogenetic sequences analysis, multiple sequences alignment, and anthocyanin content together showed that the expression changes of FcGSTF1, and FcGSTU5/6/7 may play crucial roles in fruit peel color alteration during fruit ripening. Our study provides a comprehensive overview of the GST gene family in fig, thus facilitating the further clarification of the molecular function and breeding utilization.

AtGSTU19 and AtGSTU24 as Moderators of the Response of Arabidopsis thaliana to Turnip mosaic virus

Plants produce glutathione as a response to the intercellular redox state. Glutathione actively participates in the reactive oxygen species (ROS)-dependent signaling pathway, especially under biotic stress conditions. Most of the glutathione S-transferases (GSTs) are induced in cells during the defense response of plants not only through highly specific glutathione-binding abilities but also by participating in the signaling function. The tau class of GSTs has been reported to be induced as a response under stress conditions. Although several studies have focused on the role of the tau class of GSTs in plant–pathogen interactions, knowledge about their contribution to the response to virus inoculation is still inadequate. Therefore, in this study, the response of Atgstu19 and Atgstu24 knockout mutants to mechanical inoculation of Turnip mosaic virus (TuMV) was examined. The systemic infection of TuMV was more dynamically promoted in Atgstu19 mutants than in wild-type (Col-0) plants, suggesting the role of GSTU19 in TuMV resistance. However, Atgstu24 mutants displayed virus limitation and downregulation of the relative expression of TuMV capsid protein, accompanied rarely by TuMV particles only in vacuoles, and ultrastructural analyses of inoculated leaves revealed the lack of virus cytoplasmic inclusions. These findings indicated that Atgstu24 mutants displayed a resistance-like reaction to TuMV, suggesting that GSTU24 may suppress the plant resistance. In addition, these findings confirmed that GSTU1 and GSTU24 are induced and contribute to the susceptible reaction to TuMV in the Atgstu19–TuMV interaction. However, the upregulation of GSTU19 and GSTU13 highly correlated with virus limitation in the resistance-like reaction in the Atgstu24–TuMV interaction. Furthermore, the highly dynamic upregulation of GST and glutathione reductase (GR) activities resulted in significant induction (between 1 and 14 days post inoculation [dpi]) of the total glutathione pool (GSH + GSSG) in response to TuMV, which was accompanied by the distribution of active glutathione in plant cells. On the contrary, in Atgstu19, which is susceptible to TuMV interaction, upregulation of GST and GR activity only up to 7 dpi symptom development was reported, which resulted in the induction of the total glutathione pool between 1 and 3 dpi. These observations indicated that GSTU19 and GSTU24 are important factors in modulating the response to TuMV in Arabidopsis thaliana. Moreover, it was clear that glutathione is an important component of the regulatory network in resistance and susceptible response of A. thaliana to TuMV. These results help achieve a better understanding of the mechanisms regulating the Arabidopsis–TuMV pathosystem.

Improvement of Stevia rebaudiana Bertoni In Vitro Propagation and Steviol Glycoside Content Using Aminoacid Silver Nanofibers

The food industry is interested in replacing artificial sweeteners with natural sugars that possess zero calories and carbohydrates and do not cause spikes in blood sugar levels. The steviosides leaves, synthesized at Stevia rebaudiana Bertoni, are 300 times sweeter than common table sugar. Stevia propagation is limited due to the poor viability of the seeds, the long time and low germination rate, and the poor rooting ability of vegetative cuttings. Because of this, an alternative biotechnological method for its reproduction is being studied, such as multiple shoot production through direct organogenesis using nanofibers, formed from a derivative of amino acid valine as a carrier of the biologically active agent silver atoms/particles (NF-1%Ag and NF-2%Ag). The stevia explants were cultured on a medium containing NF-1%Ag and NF-2%Ag at concentrations of 1, 10, 50, and 100 mg L⁻¹. The NF-1%Ag and NF-2%Ag treatment caused hormetic effects on stevia plantlets. At low concentrations of from 1 to 50 mg L⁻¹ of nanofibers, the stimulation of plant growth was observed, with the maximum effect being observed at 50 mg L⁻¹ nanofibers. However, at the higher dose of 100 mg L⁻¹, inhibition of the values of parameters characterizing plant growth was recorded. The presence of nanofibers in the medium stimulates stevia root formatting.

Evaluation of Cd2+ stress tolerance in transgenic rice overexpressing PgGPx gene that maintains cellular ion and reactive oxygen species homeostasis

Non-essential toxic heavy metal like cadmium (Cd2+) interferes with the plant growth and development in many ways. Cd2+ travels via plant transportation system, specifically through xylem and may integrate into the food chain causing unfavorable condition in human health. Therefore, strategies to develop Cd2+ tolerance and less accumulation in the plant system require urgent attention. Peroxidase gene family is known for metal ions transportation including Cd2+ and thus plays an important role in ion homeostasis. Previously, we have reported the presence of a Cd2+ dependent functional peroxiredoxin from Pennisetum glaucum (PgGPx). The present study elucidates the role of this PgGPx against Cd2+ stress in rice. The transcript levels of PgGPx were found to be highly upregulated in response to exogenous Cd2+. Moreover, recombinant PgGPx protein showed significant glutathione S-transferase activity in vitro. Ectopically expressed PgGPx in transgenic rice plants showed tolerance towards Cd2+ stress as demonstrated by several physiological indices including shoot and root length, biomass, chlorophyll, and hydrogen peroxide content. Moreover, these transgenic plants also showed enhanced capability to cope up with oxidative stress by enhancing the activity of different antioxidant enzymes including Superoxide dismutase, Catalase, Ascorbate peroxidase, Glutathione peroxidase, Glutathione reductase) in response to Cd2+. Hence, maintenance of cellular ion homeostasis and modulation of reactive oxygen species-scavenging pathway are found to be improved by overexpression of PgGPx under Cd2+ stress. These results will pave the way to develop strategies for engineering Cd2+ stress tolerance in economically important crop plants.

γ-Aminobutyric acid (GABA) improves pesticide detoxification in plants

It is important to ensure food safety to study the technology and mechanism of pesticide residues degradation in crops. Though γ-aminobutyric acid (GABA) has been widely reported to involve in plant stress resistance, whether exogenous application or endogenous regulation of GABA by gene-editing technology can promote the pesticide detoxification is not clear in plants. Using tomato and chlorothalonil (CHT) as research models, we discovered that exogenous application of GABA or endogenous elevation of GABA by knockout of pyruvate-dependent GABA transaminase promoted both CHT metabolism and plant stress tolerance to CHT. This is closely related to the active adaptation of GABA to CHT stress by regulating the plant GABA shunt pathway and polyamine pathway. The transcriptome data revealed 17 target genes that may be closely related to the involvement of GABA in CHT metabolism, including 4 peroxidases, 5 glycosyltransferases, 4 glutathione S-transferases, and 4 ABC transporters. In addition, the glutathione detoxification pathway and antioxidative enzyme also actively participated in the GABA-induced CHT detoxification process, which played an important role in relieving CHT stress. As a result, GABA significantly increased the photosynthetic capacity of tomato leaves under CHT stress. While studying photosynthesis, we unexpectedly found that GABA promotes stomatal closure in terms of decreased stomatal conductance and stomatal diameter. This result implies that GABA can reduce CHT absorption by regulating stomatal movement in leaves. Together, we provided a novel viewpoint that foliar application of GABA or metabolic engineering of GABA is an effective approach to reduce the risk of pesticide contamination in crop production.

Putative Protein Discovery from Microalgal Genomes as a Synthetic Biology Protein Library for Heavy Metal Bio-Removal

Simple Summary

Nowadays, heavy metal polluted wastewater is one of the global challenges that leads to an insufficient supply of clean water. Taking advantage of what nature has to offer, several organisms, including microalgae, can natively bioremediate these heavy metals. However, the effectiveness of such processes does not meet expectations, especially with the increasing amount of pollution in today’s world. Therefore, with the goal of creating effective strains, synthetic biology via bioengineering is widely used as a strategy to enhance the heavy metal bio-removing capability, either by directly engineering the native ability of organisms or by transferring the ability to a more suitable host. In order to do so, a list of genes or proteins involved in the processes is crucial for stepwise engineering. Yet, a large amount of information remains to be discovered. In this work, a comprehensive library of putative proteins that are involved in heavy metal bio-removal from microalgae was constructed. Moreover, with the development of machine learning, the 3D structures of these proteins are also predicted, using machine learning-based methods, to aid the use of synthetic biology further.

Abstract

Synthetic biology is a principle that aims to create new biological systems with particular functions or to redesign the existing ones through bioengineering. Therefore, this principle is often utilized as a tool to put the knowledge learned to practical use in actual fields. However, there is still a great deal of information remaining to be found, and this limits the possible utilization of synthetic biology, particularly on the topic that is the focus of the present work—heavy metal bio-removal. In this work, we aim to construct a comprehensive library of putative proteins that might support heavy metal bio-removal. Hypothetical proteins were discovered from Chlorella and Scenedesmus genomes and extensively annotated. The protein structures of these putative proteins were also modeled through Alphafold2. Although a portion of this workflow has previously been demonstrated to annotate hypothetical proteins from whole genome sequences, the adaptation of such steps is yet to be done for library construction purposes. We also demonstrated further downstream steps that allow a more accurate function prediction of the hypothetical proteins by subjecting the models generated to structure-based annotation. In conclusion, a total of 72 newly discovered putative proteins were annotated with ready-to-use predicted structures available for further investigation.

Genome-wide identification and characterization of glutathione S-transferase gene family in Musa acuminata L. AAA group and gaining an insight to their role in banana fruit development

Glutathione S-transferases are a multifunctional protein superfamily that is involved in diverse plant functions such as defense mechanisms, signaling, stress response, secondary metabolism, and plant growth and development. Although the banana whole-genome sequence is available, the distribution of GST genes on banana chromosomes, their subcellular localization, gene structure, their evolutionary relation with each other, conserved motifs, and their roles in banana are still unknown. A total of 62 full-length GST genes with the canonical thioredoxin fold have been identified belonging to nine GST classes, namely tau, phi, theta, zeta, lambda, DHAR, EF1G, GHR, and TCHQD. The 62 GST genes were distributed into 11 banana chromosomes. All the MaGSTs were majorly localized in the cytoplasm. Gene architecture showed the conservation of exon numbers in individual GST classes. Multiple Em for Motif Elicitation analyses revealed few class-specific motifs and many motifs were found in all the GST classes. Multiple sequence alignment of banana GST amino acid sequences with rice, Arabidopsis, and soybean sequences revealed the Ser and Cys as conserved catalytic residues. Gene duplication analyses showed the tandem duplication as a driving force for GST gene family expansion in banana. Cis-regulatory element analysis showed the dominance of light-responsive element followed by stress- and hormone-responsive elements. Expression profiling analyses were also done by RNA-seq data. It was observed that MaGSTs are involved in various stages of fruit development. MaGSTU1 was highly upregulated. The comprehensive and organized studies of MaGST gene family provide groundwork for further functional analysis of MaGST genes in banana at molecular level and further for plant breeding approaches.

Genome wide analysis of the heavy-metal-associated (HMA) gene family in tomato and expression profiles under different stresses

The heavy-metal-associated (HMA) family plays a major role in the transportation of metals. Despite having the genome sequence of the tomato (Solanum lycopersicum), the HMA gene family has not been studied yet. In this study, we identified 48 HMA genes and categorized them into Cu/Ag P1B-ATPase and Zn/Co/Cd/Pb P1BATPase sub-families according to their phylogenic relationship with Arabidopsis and rice. The SlHMA genes were distributed throughout the 12 chromosomes. Analysis of gene structure, chromosomal position, and synteny, revealed that segmental duplications bestowed their evolution. The high numbers of stress-related cis-elements were found to be present in the putative promoter regions indicate the involvement of SlHMAs in stress modulation pathways. RNA-seq data revealed that SlHMAs had divergent expression in different tissues and developmental stages, where members of Cu/Ag P1B-ATPase subfamily were strongly expressed in the roots. RT-qPCR analysis of nine selected SlHMAs showed that most of the genes were up-regulated in response to heavy metals and moderately regulated in response to different abiotic stresses such as salt, drought, and cold.

Transcriptome sequencing reveals the differentially expressed lncRNAs and mRNAs in response to cold acclimation and cold stress in Pomacea canaliculata

Background

Tolerance of low temperature has a significant impact on survival and expansion of invasive snail Pomacea canalicuata. Cold acclimation can enhance cold tolerance of Pomacea canalicuata. To elucidate the molecular mechanism of P. canaliculata’s responses to cold acclimation and cold stress, a high-throughput transcriptome analysis of P. canaliculata was performed, and gene expression following artificial cold acclimation and then cold stress at 0 °C for 24 h was compared using RNA sequencing.

Results

Using the Illumina platform, we obtained 151.59 G subreads. A total of 5,416 novel lncRNAs were identified, and 3166 differentially expressed mRNAs and 211 differentially expressed lncRNAs were screened with stringent thresholds. The potential antisense, cis and trans targets of lncRNAs were predicted. Kyoto Encyclopedia of Genes and Genomes enrichment analysis showed that many target genes were involved in proteasome, linoleic acid metabolism and retinol metabolism under cold acclimation. The lncRNA of P. canaliculata could participate in cold acclimation by regulating the expression of E3 ubiquitin protein ligase, 26S proteasome non-ATPase dependent regulation subunit, glutathione S-transferase, sodium/glucose cotransporter and cytochrome P450.

Conclusions

These results broaden our understanding of cold acclimation and cold stress associated lncRNAs and mRNAs, and provide new insights into lncRNA mediated regulation of P. canaliculata cold acclimation and cold stress response.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08622-5.

Molecular Cloning of a TCHQD Class Glutathione S-Transferase and GST Function in Response to GABA Induction of Melon Seedlings under Root Hypoxic Stress

Glutathione-S-transferase (GST), a versatile enzyme that occurs widely in plants, plays a key role in plant resistance to environmental stresses. Previous results have demonstrated that GST proteins are involved in alleviating root hypoxic injury caused by gamma-aminobutyric acid (GABA); however, the induction mechanism of the GST gene in the melon under root hypoxic stress and its functional mechanisms remain unclear. In this study, based on gene cloning and bioinformatics analysis, GST gene expression and activity and glutathione (GSH) content were assessed under root hypoxic and normoxic conditions with or without GABA. The results showed that the CmGST locus includes an 804 bp gene sequence that encodes 267 amino acids. The sequence was highly similar to those of other plant TCHQD GSTs, and the highest value (94%) corresponded to Cucumis sativus. Real-time PCR results showed that the CmGST gene was induced by root hypoxic stress and GABA, and this induction was accompanied by increased GST activity and GSH content. Root hypoxic stress significantly upregulated CmGST expression in melon roots (0.5–6 d), stems, and leaves (0.5–4 d), and GST activity and GSH content were also significantly increased. Exogenous GABA treatment upregulated CmGST gene expression, GST activity, and GSH content, particularly under root hypoxic conditions. As a result, CmGST expression in GABA-treated roots and leaves at 0.5–4 d and stems at 0.5–6 d was significantly higher than that under root hypoxic stress alone. This study provides evidence that the TCHQD CmGST may play a vital role in how GABA increases melon hypoxia tolerance by upregulating gene expression and improving metabolism.

Role of Promising Secondary Metabolites to Confer Resistance Against Environmental Stresses in Crop Plants: Current Scenario and Future Perspectives

Plants often face incompatible growing environments like drought, salinity, cold, frost, and elevated temperatures that affect plant growth and development leading to low yield and, in worse circumstances, plant death. The arsenal of versatile compounds for plant consumption and structure is called metabolites, which allows them to develop strategies to stop enemies, fight pathogens, replace their competitors and go beyond environmental restraints. These elements are formed under particular abiotic stresses like flooding, heat, drought, cold, etc., and biotic stress such as a pathogenic attack, thus associated with survival strategy of plants. Stress responses of plants are vigorous and include multifaceted crosstalk between different levels of regulation, including regulation of metabolism and expression of genes for morphological and physiological adaptation. To date, many of these compounds and their biosynthetic pathways have been found in the plant kingdom. Metabolites like amino acids, phenolics, hormones, polyamines, compatible solutes, antioxidants, pathogen related proteins (PR proteins), etc. are crucial for growth, stress tolerance, and plant defense. This review focuses on promising metabolites involved in stress tolerance under severe conditions and events signaling the mediation of stress-induced metabolic changes are presented.

Genome-wide identification of glutathione S-transferase gene family members in tea plant (Camellia sinensis) and their response to environmental stress

Glutathione S-transferases (GSTs) are ubiquitous enzymes involved in the regulation of plant growth, development, and stress responses. Unfortunately, the comprehensive identification of GSTs in tea plant has not been achieved. In this study, a total of 88 CsGSTs proteins were identified and divided into eight classes, among which the tau class was the largest. Chromosomal localization analysis revealed an uneven distribution of CsGSTs across the tea plant genome. Tandem duplication is the main force driving tea plant CsGSTs expansion. CsGSTs structures and conserved motifs were similar. The analysis of cis-regulatory elements in promoter regions showed that CsGSTs can response to multiple stresses, and that MYB may be involved in the transcriptional regulation of CsGST. RNA-Seq data revealed that the expression of most GSTUs was associated with various stresses, including pathogen and insect attack, cold spells, drought and salt stresses, nitrogen nutrition, bud dormancy, and morphological development, and the expression of these CsGSTs was obviously different in eight tissues. In addition, we proved that CsGSTU19, localized at the nucleus and cell membrane, was involved in tea plant defense against temperature stresses and Co. camelliae infection. These findings provide references for the further functional analysis of GSTs in the future.

Potential Therapeutic Implications of Caffeic Acid in Cancer Signaling: Past, Present, and Future

Caffeic acid (CA) has been present in many herbs, vegetables, and fruits. CA is a bioactive compound and exhibits various health advantages that are linked with its anti-oxidant functions and implicated in the therapy and prevention of disease progression of inflammatory diseases and cancer. The anti-tumor action of CA is attributed to its pro-oxidant and anti-oxidant properties. CA’s mechanism of action involves preventing reactive oxygen species formation, diminishing the angiogenesis of cancer cells, enhancing the tumor cells’ DNA oxidation, and repressing MMP-2 and MMP-9. CA and its derivatives have been reported to exhibit anti-carcinogenic properties against many cancer types. CA has indicated low intestinal absorption, low oral bioavailability in rats, and pitiable permeability across Caco-2 cells. In the present review, we have illustrated CA’s therapeutic potential, pharmacokinetics, and characteristics. The pharmacological effects of CA, the emphasis on in vitro and in vivo studies, and the existing challenges and prospects of CA for cancer treatment and prevention are discussed in this review.

Identification of New QTLs for Dietary Fiber Content in Aegilops biuncialis

Grain dietary fiber content is an important health-promoting trait of bread wheat. A dominant dietary fiber component of wheat is the cell wall polysaccharide arabinoxylan and the goatgrass Aegilops biuncialis has high β-glucan content, which makes it an attractive gene source to develop wheat lines with modified fiber composition. In order to support introgression breeding, this work examined genetic variability in grain β-glucan, pentosan, and protein content in a collection of Ae. biuncialis. A large variation in grain protein and edible fiber content was revealed, reflecting the origin of Ae. biuncialis accessions from different eco-geographical habitats. Association analysis using DArTseq-derived SNPs identified 34 QTLs associated with β-glucan, pentosan, water-extractable pentosan, and protein content. Mapping the markers to draft chromosome assemblies of diploid progenitors of Ae. biuncialis underlined the role of genes on chromosomes 1M^b, 4M^b, and 5M^b in the formation of grain β-glucan content, while other QTLs on chromosome groups 3, 6, and 1 identified genes responsible for total- and water-extractable pentosan content. Functional annotation of the associated marker sequences identified fourteen genes, nine of which were identified in other monocots. The QTLs and genes identified in the present work are attractive targets for chromosome-mediated gene transfer to improve the health-promoting properties of wheat-derived foods.

Glutathione Modulation in PVYNTN Susceptible and Resistant Potato Plant Interactions

Glutathione is a metabolite that plays an important role in plant response to biotic stress through its ability to remove reactive oxygen species, thereby limiting the degree of potential oxidative damage. It can couple changes in the intracellular redox state to the development, especially the defense responses, of plants. Several studies have focused on measuring glutathione levels in virus infected plants, but have not provided complete information. Therefore, we analyzed, for the first time, the content of glutathione as well as its ultrastructural distribution related to susceptible and hypersensitive potato–Potato virus Y NTN (PVY^NTN) interaction, with an aim of providing new insight into interactive responses to PVY^NTN stress. Our findings reported that the inoculation of PVY^NTN caused a dynamic increase in the content of glutathione, not only in resistance but also in susceptible reaction, especially at the first steps of plant–virus interaction. Moreover, the increase in hypersensitive response was much more dynamic, and accompanied by a significant reduction in the content of PVY^NTN. By contrast, in susceptible potato Irys, the content of glutathione decreased between 7 and 21 days after virus inoculation, which led to a significant increase in PVY^NTN concentration. Additionally, our findings clearly indicated the steady induction of two selected potato glutathione S-transferase StGSTF1 and StGSTF2 genes after PVY^NTN inoculation, regardless of the interaction type. However, the relative expression level of StGSTF1 did not significantly differ between resistant and susceptible plants, whereas the relative expression levels of StGSTF2 differed between susceptible and resistant reactions. Therefore, we proposed that StGSTF2 can act as a marker of the type of response to PVY^NTN. Our observations indicated that glutathione is an important component of signaling as well as the regulatory network in the PVY^NTN–potato pathosystem. In resistance responses to PVY^NTN, this metabolite activates plant defenses by reducing potential damage to the host plant cell, causing a reduction in virus concentration, while it can also be involved in the development of PVY^NTN elicited symptoms, as well as limiting oxidative stress, leading to systemic infection in susceptible potato plants.

A Sweet Cherry Glutathione S-Transferase Gene, PavGST1, Plays a Central Role in Fruit Skin Coloration

Sweet cherry, an economically important horticultural crop, has strong antioxidant activity. The fruits contain compounds potentially beneficial to human health—particularly anthocyanins, which are synthesized in cytosol and predominantly accumulated in vacuoles. Although anthocyanin levels differ among dark-red, blush, and yellow sweet cherry cultivars, the regulatory mechanism of anthocyanin transport and accumulation is not well understood in this species. In this study, we identified 53 glutathione S-transferase genes (PavGSTs) from sweet cherry and found that PavGST1 expression was well correlated with anthocyanin accumulation in cultivars with different fruit skin colors. TRV-mediated virus-induced silencing of PavGST1 decreased anthocyanin accumulation in sweet cherry fruits and downregulated the expressions of anthocyanin biosynthetic and regulatory genes. In addition, transient overexpression of PavGST1 promoted anthocyanin accumulation. Furthermore, yeast one-hybrid and dual-luciferase assays revealed that PavMYB10.1 and PavMYB75 directly bind to different MYB binding sites of the PavGST1 promoter (MBS-1 and MBS-3) to activate PavGST1 transcription. According to our results, PavGST1 plays a central role in sweet cherry fruit anthocyanin accumulation. Our findings provide novel insights into the coordinative regulatory mechanisms of PavGST1 and PavMYBs in anthocyanin accumulation in sweet cherry.

Genome-Wide Identification, Evolution and Expression Analysis of the Glutathione S-Transferase Supergene Family in Euphorbiaceae

Euphorbiaceae, a family of plants mainly grown in the tropics and subtropics, is also widely distributed all over the world and is well known for being rich in rubber, oil, medicinal materials, starch, wood and other economically important plant products. Glutathione S-transferases (GSTs) constitute a family of proteins encoded by a large supergene family and are widely expressed in animals, bacteria, fungi and plants, but with few reports of them in Euphorbiaceae plants. These proteins participate in and regulate the detoxification and oxidative stress response of heterogeneous organisms, resistance to stress, growth and development, signal transduction and other related processes. In this study, we identified and analyzed the whole genomes of four species of Euphorbiaceae, namely Ricinus communis, Jatropha curcas, Hevea brasiliensis, and Manihot esculenta, which have high economic and practical value. A total of 244 GST genes were identified. Based on their sequence characteristics and conserved domain types, the GST supergene family in Euphorbiaceae was classified into 10 subfamilies. The GST supergene families of Euphorbiaceae and Arabidopsis have been found to be highly conserved in evolution, and tandem repeats and translocations in these genes have made the greatest contributions to gene amplification here and have experienced strong purification selection. An evolutionary analysis showed that Euphorbiaceae GST genes have also evolved into new subtribes (GSTO, EF1BG, MAPEG), which may play a specific role in Euphorbiaceae. An analysis of expression patterns of the GST supergene family in Euphorbiaceae revealed the functions of these GSTs in different tissues, including resistance to stress and participation in herbicide detoxification. In addition, an interaction analysis was performed to determine the GST gene regulatory mechanism. The results of this study have laid a foundation for further analysis of the functions of the GST supergene family in Euphorbiaceae, especially in stress and herbicide detoxification. The results have also provided new ideas for the study of the regulatory mechanism of the GST supergene family, and have provided a reference for follow-up genetics and breeding work.

Potential Therapeutic Implications of Caffeic Acid in Cancer Signaling: Past, Present, and Future

Caffeic acid (CA) has been present in many herbs, vegetables, and fruits. CA is a bioactive compound and exhibits various health advantages that are linked with its anti-oxidant functions and implicated in the therapy and prevention of disease progression of inflammatory diseases and cancer. The anti-tumor action of CA is attributed to its pro-oxidant and anti-oxidant properties. CA’s mechanism of action involves preventing reactive oxygen species formation, diminishing the angiogenesis of cancer cells, enhancing the tumor cells’ DNA oxidation, and repressing MMP-2 and MMP-9. CA and its derivatives have been reported to exhibit anti-carcinogenic properties against many cancer types. CA has indicated low intestinal absorption, low oral bioavailability in rats, and pitiable permeability across Caco-2 cells. In the present review, we have illustrated CA’s therapeutic potential, pharmacokinetics, and characteristics. The pharmacological effects of CA, the emphasis onin vitro and in vivostudies, and the existing challenges and prospects of CA for cancer treatment and prevention are discussed in this review.

Exploration of glutathione reductase for abiotic stress response in bread wheat (Triticum aestivum L.)

A total of seven glutathione reductase (GR) genes were identified in Triticum aestivum, which were used for comparative structural characterization, phylogenetic analysis and expression profiling with the GR genes of other cereal plants. The modulated gene expression and enzyme activity revealed the role of GRs in abiotic stress response in T. aestivum. Glutathione reductase (GR) is an enzymatic antioxidant that converts oxidized glutathione (GSSG) into reduced glutathione (GSH) through the ascorbate-glutathione cycle. In this study, a total of seven GR genes forming two homeologous groups were identified in the allohexaploid genome of bread wheat (Triticum aestivum). Besides, we identified three GR genes in each Aegilops tauschii, Brachypodium distachyon, Triticum urartu and Sorghum bicolor, which were used for comparative characterization. Phylogenetic analysis revealed the clustering of GR proteins into two groups; class I and class II, which were predicted to be localized in cytoplasm and chloroplast, respectively. The exon-intron and conserved motif patterns were almost conserved in each group, in which a maximum of 10 and 17 exons were present in chloroplastic and cytoplasmic GRs, respectively. The protein structure analysis confirmed the occurrence of conserved pyridine nucleotide disulfide oxidoreductase (Pyr_redox) and pyridine nucleotide disulfide oxidoreductase dimerization (Pyr_redox_dim) domains in each GR. The active site of GR proteins consisted of two conserved cysteine residues separated by four amino acid residues. Promoter analysis revealed the occurrence of growth and stress-related cis-active elements. Tissue-specific expression profiling suggested the involvement of GRs in both vegetative and reproductive tissue development in various plants. The differential expression of TaGR genes and enhanced GR enzyme activity suggested their roles under drought, heat, salt and arsenic stress. Interaction of GRs with other proteins and chemical compounds of the ascorbate-glutathione cycle revealed their coordinated functioning. The current study will provide a foundation for the validation of the precise role of each GR gene in future studies.

Drought tolerance improvement in Solanum lycopersicum: an insight into "OMICS" approaches and genome editing

Solanum lycopersicum (tomato) is an internationally acclaimed vegetable crop that is grown worldwide. However, drought stress is one of the most critical challenges for tomato production, and it is a crucial task for agricultural biotechnology to produce drought-resistant cultivars. Although breeders have done a lot of work on the tomato to boost quality and quantity of production and enhance resistance to biotic and abiotic stresses, conventional tomato breeding approaches have been limited to improving drought tolerance because of the intricacy of drought traits. Many efforts have been made to better understand the mechanisms involved in adaptation and tolerance to drought stress in tomatoes throughout the years. "Omics" techniques, such as genomics, transcriptomics, proteomics, and metabolomics in combination with modern sequencing technologies, have tremendously aided the discovery of drought-responsive genes. In addition, the availability of biotechnological tools, such as plant transformation and the recently developed genome editing system for tomatoes, has opened up wider opportunities for validating the function of drought-responsive genes and the generation of drought-tolerant varieties. This review highlighted the recent progresses for tomatoes improvement against drought stress through "omics" and "multi-omics" technologies including genetic engineering. We have also discussed the roles of non-coding RNAs and genome editing techniques for drought stress tolerance improvement in tomatoes.

Genomic Analysis of the Glutathione S-Transferase Family in Pear (Pyrus communis) and Functional Identification of PcGST57 in Anthocyanin Accumulation

Anthocyanin accumulation in vacuoles results in red coloration in pear peels. Glutathione S-transferase (GST) proteins have emerged as important regulators of anthocyanin accumulation. Here, a total of 57 PcGST genes were identified in the European pear ‘Bartlett’ (Pyrus communis) through comprehensive genomic analysis. Phylogenetic analysis showed that PcGST genes were divided into 10 subfamilies. The gene structure, chromosomal localization, collinearity relationship, cis-elements in the promoter region, and conserved motifs of PcGST genes were analyzed. Further research indicated that glutamic acid (Glu) can significantly improve anthocyanin accumulation in pear peels. RNA sequencing (RNA-seq) analysis showed that Glu induced the expression of most PcGST genes, among which PcGST57 was most significantly induced. Further phylogenetic analysis indicated that PcGST57 was closely related to GST genes identified in other species, which were involved in anthocyanin accumulation. Transcript analysis indicated that PcGST57 was expressed in various tissues, other than flesh, and associated with peel coloration at different developmental stages. Silencing of PcGST57 by virus-induced gene silencing (VIGS) inhibited the expression of PcGST57 and reduced the anthocyanin content in pear fruit. In contrast, overexpression of PcGST57 improved anthocyanin accumulation. Collectively, our results demonstrated that PcGST57 was involved in anthocyanin accumulation in pear and provided candidate genes for red pear breeding.

Identification and Comprehensive Genome-Wide Analysis of Glutathione S-Transferase Gene Family in Sweet Cherry (Prunus avium) and Their Expression Profiling Reveals a Likely Role in Anthocyanin Accumulation

Glutathione S-transferases (GSTs) in plants are multipurpose enzymes that are involved in growth and development and anthocyanins transportation. However, members of the GST gene family were not identified in sweet cherry (Prunus avium). To identify the GST genes in sweet cherry, a genome-wide analysis was conducted. In this study, we identified 67 GST genes in P. avium genome and nomenclature according to chromosomal distribution. Phylogenetic tree analysis revealed that PavGST genes were classified into seven chief subfamily: TCHQD, Theta, Phi, Zeta, Lambda, DHAR, and Tau. The majority of the PavGST genes had a relatively well-maintained exon-intron and motif arrangement within the same group, according to gene structure and motif analyses. Gene structure (introns-exons) and conserved motif analysis revealed that the majority of the PavGST genes showed a relatively well-maintained motif and exons-introns configuration within the same group. The chromosomal localization, GO enrichment annotation, subcellular localization, syntenic relationship, Ka/Ks analysis, and molecular characteristics were accomplished using various bioinformatics tools. Mode of gene duplication showed that dispersed duplication might play a key role in the expansion of PavGST gene family. Promoter regions of PavGST genes contain numerous cis-regulatory components, which are involved in multiple stress responses, such as abiotic stress and phytohormones responsive factors. Furthermore, the expression profile of sweet cherry PavGSTs showed significant results under LED treatment. Our findings provide the groundwork for future research into induced LED anthocyanin and antioxidants deposition in sweet cherries.

Crosstalk between the redox signalling and the detoxification: GSTs under redox control?

Reactive oxygen species (ROS), antioxidants and their reduction-oxidation (redox) states all contribute to the redox homeostasis, but glutathione is considered to be the master regulator of it. We aimed to understand the relationship between the redox potential and the diverse glutathione transferase (GST) enzyme family by comparing the stress responses of two tomato cultivars (Solanum lycopersicum 'Moneymaker' and 'Ailsa Craig'). Four-week-old plants were treated by two concentrations of mannitol, NaCl and salicylic acid. The lower H₂O₂ and malondialdehyde contents indicated higher stress tolerance of 'Moneymaker'. The redox status of roots was characterized by measuring the reduced and oxidized form of ascorbate and glutathione spectrophotometrically after 24 h. The redox potential of 'Ailsa Craig' was more oxidized compared to 'Moneymaker' even under control conditions and became more positive due to treatments. High-throughput quantitative real-time PCR revealed that besides overall higher expression levels, SlGSTs were activated more efficiently in 'Moneymaker' due to stresses, resulting in generally higher GST and glutathione peroxidase activities compared to 'Ailsa Craig'. The expression level of SlGSTs correlated differently, however Pearson's correlation analysis showed usually strong positive correlation between SlGST transcription and glutathione redox potential. The possible redox regulation of SlGST expressions was discussed.

Caffeic acid, a dietary polyphenol, as a promising candidate for combination therapy

Increased effectiveness and decreasing toxicity are prime objectives in drug research. Overwhelming evidence suggests the use of appropriate combination therapy for the better efficacy of drugs owing to their synergistic profile. Dietary active constituents play a major role in health outcomes. Therefore, it is possible to increase the effectiveness of the drug by combining contemporary medication with active natural/semi-synthetic constituents. One such dietary constituent, caffeic acid (CA), is a by-product of the shikimate pathway in plants and is a polyphenol of hydroxycinnamic acid class. Extensive research on CA has proposed its efficacy against inflammatory, neurodegenerative, oncologic, and metabolic disorders. The synergistic/additive effects of CA in combination with drugs like caffeine, metformin, pioglitazone, and quercetin have been reported in several experimental models and thus the present review is an attempt to consolidate outcomes of this research. Multi-target-based mechanistic studies will facilitate the development of effective combination regimens of CA.

Specific glutathione-S-transferases ensure an efficient detoxification of diclofenac in Solanum lycopersicum L. plants

Diclofenac (DCF) is a very common pharmaceutical that, due to its high use and low removal rate, is considered a prominent contaminant in surface and groundwater worldwide. In this study, Solanum lycopersicum L. cv. Micro-Tom (tomato) was used to disclose the role of glutathione (GSH)-related enzymes, as GSH conjugation with DCF is a well reported detoxification mechanism in mammals and some plant species. To achieve this, S. lycopersicum plants were exposed to 0.5 and 5 mg L^-1 of DCF for 5 weeks under a semi-hydroponic experiment. The results here obtained point towards an efficient DCF detoxification mechanism that prevents DCF bioaccumulation in fruits, minimizing any concerns for human health. Although a systemic response seems to be present in response to DCF, the current data also shows that its detoxification is mostly a root-specific process. Furthermore, it appears that GSH-mediated DCF detoxification is the main mechanism activated, as glutathione-S-transferase (GST) activity was greatly enhanced in roots of tomato plants treated with 5 mg L^-1 DCF, accompanied by increased glutathione reductase activity, responsible for GSH regeneration. By applying a targeted gene expression analysis, we provide evidence, for the first time, that SlGSTF4 and SlGSTF5 genes, coding for GSTs from phi class, were the main players driving the conjugation of this contaminant. In this sense, and even though tomato plants appear to be somewhat tolerant to DCF exposure, research on GST activity can prove to be instrumental in remediating DCF-contaminated environments and improving plant growth under such conditions.

Genome-Wide Identification and Evolutionary Analysis of the SRO Gene Family in Tomato

SRO (SIMILAR TO RCD ONE) is a family of plant-specific small molecule proteins that play an important role in plant growth and development and environmental responses. However, SROs still lack systematic characterization in tomato. Based on bioinformatics methods, SRO family genes were identified and characterized from cultivated tomatoes and several wild tomatoes. qRT-PCR was used to study the expression of SRO gene in cultivated tomatoes. Phylogenetic and evolutionary analyses showed that SRO genes in angiosperms share a common ancestor and that the number of SRO family members changed as plants diverged and evolved. Cultivated tomato had six SRO members, five of which still shared some degree of identity with the ancestral SRO genes. Genetic structure and physicochemical properties showed that tomato SRO genes were highly conserved with chromosomal distribution. They could be divided into three groups based on exon-intron structure, and cultivated tomato contained only two of these subclades. A number of hormonal, light and abiotic stress-responsive cis-regulatory elements were identified from the promoter of the tomato SRO gene, and they also interacted with a variety of stress-responsive proteins and microRNAs. RNA-seq analysis showed that SRO genes were widely expressed in different tissues and developmental stages of tomato, with significant tissue-specific features. Expression analysis also showed that SRO genes respond significantly to high temperature and salt stress and mediate the tomato hormone regulatory network. These results provide a theoretical basis for further investigation of the functional expression of tomato SRO genes and provide potential genetic resources for tomato resistance breeding.

Time-course transcriptomic analysis of Petunia ×hybrida leaves under water deficit stress using RNA sequencing

Water deficit limits plant growth and development, resulting in quality loss of horticultural crops. However, there is limited information on gene regulation and signaling pathways related to water deficit stress response at multiple time points. The objective of this research was to investigate global gene expression patterns under water deficit stress to provide an insight into how petunia (Petunia ×hybrida 'Mitchell Diploid') responded in the process of stress. Nine-week-old petunias were irrigated daily or placed under water stress by withholding water. Stressed plants reduced stomatal conductance after five days of water deficit, indicating they perceived stress and initiated stress response mechanisms. To analyze transcriptomic changes at the early stage of water deficit, leaf tissue samples were collected 1, 3, and 5 days after water was withheld for RNA sequencing. Under water deficit stress, 154, 3611, and 980 genes were upregulated and 41, 2806, and 253 genes were downregulated on day 1, 3, and 5, respectively. Gene Ontology analysis revealed that redox homeostasis processes through sulfur and glutathione metabolism pathways, and hormone signal transduction, especially abscisic acid and ethylene, were enriched under water deficit stress. Thirty-four transcription factor families were identified, including members of AP2/ERF, NAC, MYB-related, C2H2, and bZIP families, and TFs in AP2/ERF family was the most abundant in petunia. Interestingly, only one member of GRFs was upregulated on day 1, while most of TFs were differentially expressed on day 3 and/or 5. The transcriptome data from this research will provide valuable molecular resources for understanding the early stages of water stress-responsive networks as well as engineering petunia with enhanced water stress tolerance.

Effects of conserved Arg20, Glu74 and Asp77 on the structure and function of a tau class glutathione S-transferase in rice

The relative position of domains is critical for enzymatic properties of tau class glutathione S-transferases, and altering the position of linker far away from the active center affects catalytic property. Glutathione S-transferases (GSTs) are a family of phase II detoxification enzymes whose main function is to improve plant resistance to stresses. To understand the structural effects of tau class GSTs on their function, using OsGSTU17 as an example, we predicted the residues involved in the interactions between its domains and linker region. We further detected the structural changes in mutants and the corresponding changes in terms of substrate activity and kinetic parameters. Four pairs of residues, including Ala14 and Trp165, Arg20 and Tyr154, Glu74 and Arg98, Asp77 and Met87, forming hydrogen bonds and salt bridges were found to play important roles in maintaining the relative position between the domains and linker region inside the protein. The hydrogen bond between Trp165 and Ala14 affected the structural stability has been demonstrated in our previous study. The mutant R20A lost almost all catalytic activity. Interestingly, the mutant E74A exhibited a significant decrease in activity towards 7-chloro-4-nitrobenzo-2-oxa-1, 3-diazole, 1-chloro-2, 4-dinitrobenzene and 4-nitrobenzyl chloride, while its activity towards substrate cumene hydroperoxide remained unchanged. Compared with other mutants, the mutant D77A exhibited decreased affinity to its substrates and increased activity towards 1-chloro-2, 4-dinitrobenzene and cumene hydroperoxide, but its thermodynamic stability did not change significantly. The relative position of individual domain was critical for enzymatic properties, and the linker which is far away from the active site could change the enzymatic properties of GSTs via altering the relative position of the individual domain. Our results provide insights into the relationship between structure and function of tau class GSTs.

Genome-wide identification and expression profiling of glutathione S-transferase family under multiple abiotic and biotic stresses in Medicago truncatula L

Glutathione transferases (GSTs) constitute an ancient, ubiquitous, multi-functional antioxidant enzyme superfamily that has great importance on cellular detoxification against abiotic and biotic stresses as well as plant development and growth. The present study aimed to a comprehensive genome-wide identification and functional characterization of GST family in one of the economically important legume plants-Medicago truncatula. Here, we have identified a total of ninety-two putative MtGST genes that code for 120 proteins. All these members were classified into twelve classes based on their phylogenetic relationship and the presence of structural conserved domain/motif. Among them, 7 MtGST gene pairs were identified to have segmental duplication. Expression profiling of MtGST transcripts revealed their high level of organ/tissue-specific expression in most of the developmental stages and anatomical tissues. The transcripts of MtGSTU5, MtGSTU8, MtGSTU17, MtGSTU46, and MtGSTU47 showed significant up-regulation in response to various abiotic and biotic stresses. Moreover, transcripts of MtGSTU8, MtGSTU14, MtGSTU28, MtGSTU30, MtGSTU34, MtGSTU46 and MtGSTF8 were found to be highly upregulated in response to drought treatment for 24h and 48h. Among the highly stress-responsive MtGST members, MtGSTU17 showed strong affinity towards its conventional substrates reduced glutathione (GSH) and 1-chloro-2,4-dinitrobenzene (CDNB) with the lowest binding energy of-5.7 kcal/mol and -6.5 kcal/mol, respectively. Furthermore, the substrate-binding site residues of MtGSTU17 were found to be highly conserved. These findings will facilitate the further functional and evolutionary characterization of GST genes in Medicago.

Transcriptome analysis reveals that exogenous ethylene activates immune and defense responses in a high late blight resistant potato genotype

Ethylene (ET) is one of the many important signaling hormones that functions in regulating defense responses in plants. Gene expression profiling was conducted under exogenous ET application in the high late blight resistant potato genotype SD20 and the specific transcriptional responses to exogenous ET in SD20 were revealed. Analysis of differentially expressed genes (DEGs) generated a total of 1226 ET-specific DEGs, among which transcription factors, kinases, defense enzymes and disease resistance-related genes were significantly differentially expressed. GO enrichment and KEGG metabolic pathway analysis also revealed that numerous defense regulation-related genes and defense pathways were significantly enriched. These results were consistent with the interaction of SD20 and Phytophthora infestans in our previous study, indicating that exogenous ET stimulated the defense response and initiated a similar defense pathway compared to pathogen infection in SD20. Moreover, multiple signaling pathways including ET, salicylic acid, jasmonic acid, abscisic acid, auxin, cytokinin and gibberellin were involved in the response to exogenous ET, which indicates that many plant hormones work together to form a complex network to resist external stimuli in SD20. ET-induced gene expression profiling provides insights into the ET signaling transduction pathway and its potential mechanisms in disease defense systems in potato.

The basic helix-loop-helix transcription factor bHLH95 affects fruit ripening and multiple metabolisms in tomato

Ethylene signaling pathways regulate several physiological alterations that occur during tomato fruit ripening, such as changes in colour and flavour. The mechanisms underlying the transcriptional regulation of genes in these pathways remain unclear, although the role of the MADS-box transcription factor RIN has been widely reported. Here, we describe a bHLH transcription factor, SlbHLH95, whose transcripts accumulated abundantly in breaker+4 and breaker+7 fruits compared with rin (ripening inhibitor) and Nr (never ripe) mutants. Moreover, the promoter activity of SlbHLH95 was regulated by RIN in vivo. Suppression of SlbHLH95 resulted in reduced sensitivity to ethylene, decreased accumulation of total carotenoids, and lowered glutathione content, and inhibited the expression of fruit ripening- and glutathione metabolism-related genes. Conversely, up-regulation of SlbHLH95 in wild-type tomato resulted in higher sensitivity to ethylene, increased accumulation of total carotenoids, slightly premature ripening, and elevated accumulation of glutathione, soluble sugar, and starch. Notably, overexpression of SlbHLH95 in rin led to the up-regulated expression of fruit ripening-related genes (FUL1, FUL2, SAUR69, ERF4, and CNR) and multiple glutathione metabolism-related genes (GSH1, GSH2, GSTF1, and GSTF5). These results clarified that SlbHLH95 participates in the regulation of fruit ripening and affects ethylene sensitivity and multiple metabolisms targeted by RIN in tomato.