NADPH as a quality footprinting in horticultural crops marketability

TOR and SnRK1 signaling pathways manipulation for improving postharvest fruits and vegetables marketability

During postharvest life, intracellular sugar insufficiency accompanied by insufficient intracellular ATP and NADPH supply, intracellular ROS overaccumulation along with intracellular ABA accumulation arising from water shortage could be responsible for accelerating fruits and vegetables deterioration through promoting SnRK1 and SnRK2 signaling pathways while preventing TOR signaling pathway. By TOR and SnRK1 signaling pathways manipulation, sufficient intracellular ATP and NADPH providing, supporting phenols, flavonoids and anthocyanins accumulation accompanied by improving DPPH, FRAP, and ABTS scavenging capacity by enhancing phenylpropanoid pathway activity, stimulating endogenous salicylic acid accumulation and NPR1-TGA-PRs signaling pathway, enhancing fatty acids biosynthesis, elongation and unsaturation, suppressing intracellular ROS overaccumulation, and promoting endogenous sucrose accumulation could be responsible for chilling injury palliating, fungal decay alleviating, senescence delaying and sensory and nutritional quality preservation in fruits and vegetables. Therefore, TOR and SnRK1 signaling pathways manipulation during postharvest shelf life by employing eco-friendly approaches such as exogenous trehalose and ATP application or engaging biotechnological approaches such as genome editing CRISPR-Cas9 or sprayable double-stranded RNA-based RNA interference would be applicable for improving fruits and vegetables marketability.

Phytomelatonin: From Intracellular Signaling to Global Horticulture Market

Melatonin (N-acetyl-5-methoxytryptamine), a well-known mammalian hormone, has been having a great relevance in the Plant World in recent years. Many of its physiological actions in plants are leading to possible features of agronomic interest, especially those related to improvements in tolerance to stressors and in the postharvest life of fruits and vegetables. Thus, through the exogenous application of melatonin or by modifying the endogenous biosynthesis of phytomelatonin, some change can be made in the functional levels of melatonin in tissues and their responses. Also, acting in the respective phytomelatonin biosynthesis enzymes, regulating the expression of tryptophan decarboxylase (TDC), tryptamine 5-hydroxylase (T5H), serotonin N-acetyltransferase (SNAT), N-acetylserotonin O-methyltransferase (ASMT), and caffeic acid O-methyltransferase (COMT), and recently the possible action of deacetylases on some intermediates offers promising opportunities for improving fruits and vegetables in postharvest and its marketability. Other regulators/effectors such as different transcription factors, protein kinases, phosphatases, miRNAs, protein-protein interactions, and some gasotransmitters such as nitric oxide or hydrogen sulfide were also considered in an exhaustive vision. Other interesting aspects such as the role of phytomelatonin in autophagic responses, the posttranslational reprogramming by protein-phosphorylation, ubiquitylation, SUMOylation, PARylation, persulfidation, and nitrosylation described in the phytomelatonin-mediated responses were also discussed, including the relationship of phytomelatonin and several plant hormones, for chilling injury and fungal decay alleviating. The current data about the phytomelatonin receptor in plants (CAND2/PMTR1), the effect of UV-B light and cold storage on the postharvest damage are presented and discussed. All this on the focus of a possible new action in the preservation of the quality of fruits and vegetables.

In Silico RNAseq and Biochemical Analyses of Glucose-6-Phosphate Dehydrogenase (G6PDH) from Sweet Pepper Fruits: Involvement of Nitric Oxide (NO) in Ripening and Modulation

Pepper (Capsicum annuum L.) fruit is a horticultural product consumed worldwide which has great nutritional and economic relevance. Besides the phenotypical changes that pepper fruit undergo during ripening, there are many associated modifications at transcriptomic, proteomic, biochemical, and metabolic levels. Nitric oxide (NO) is a recognized signal molecule that can exert regulatory functions in diverse plant processes including fruit ripening, but the relevance of NADPH as a fingerprinting of the crop physiology including ripening has also been proposed. Glucose-6-phosphate dehydrogenase (G6PDH) is the first and rate-limiting enzyme of the oxidative phase of the pentose phosphate pathway (oxiPPP) with the capacity to generate NADPH. Thus far, the available information on G6PDH and other NADPH-generating enzymatic systems in pepper plants, and their expression during the ripening of sweet pepper fruit, is very scarce. Therefore, an analysis at the transcriptomic, molecular and functional levels of the G6PDH system has been accomplished in this work for the first time. Based on a data-mining approach to the pepper genome and fruit transcriptome (RNA-seq), four G6PDH genes were identified in pepper plants and designated CaG6PDH1 to CaG6PDH4, with all of them also being expressed in fruits. While CaG6PDH1 encodes a cytosolic isozyme, the other genes code for plastid isozymes. The time-course expression analysis of these CaG6PDH genes during different fruit ripening stages, including green immature (G), breaking point (BP), and red ripe (R), showed that they were differentially modulated. Thus, while CaG6PDH2 and CaG6PDH4 were upregulated at ripening, CaG6PDH1 was downregulated, and CaG6PDH3 was slightly affected. Exogenous treatment of fruits with NO gas triggered the downregulation of CaG6PDH2, whereas the other genes were positively regulated. In-gel analysis using non-denaturing PAGE of a 50-75% ammonium-sulfate-enriched protein fraction from pepper fruits allowed for identifying two isozymes designated CaG6PDH I and CaG6PDH II, according to their electrophoretic mobility. In order to test the potential modulation of such pepper G6PDH isozymes, in vitro analyses of green pepper fruit samples in the presence of different compounds including NO donors (S-nitrosoglutathione and nitrosocysteine), peroxynitrite (ONOO-), a hydrogen sulfide (H2S) donor (NaHS, sodium hydrosulfide), and reducing agents such as reduced glutathione (GSH) and L-cysteine (L-Cys) were assayed. While peroxynitrite and the reducing compounds provoked a partial inhibition of one or both isoenzymes, NaHS exerted 100% inhibition of the two CaG6PDHs. Taken together these data provide the first data on the modulation of CaG6PDHs at gene and activity levels which occur in pepper fruit during ripening and after NO post-harvest treatment. As a consequence, this phenomenon may influence the NADPH availability for the redox homeostasis of the fruit and balance its active nitro-oxidative metabolism throughout the ripening process.

NADP-Dependent Malic Enzyme Genes in Sweet Pepper Fruits: Involvement in Ripening and Modulation by Nitric Oxide (NO)

NADPH is an indispensable cofactor in a wide range of physiological processes that is generated by a family of NADPH dehydrogenases, of which the NADP-dependent malic enzyme (NADP-ME) is a member. Pepper (Capsicum annuum L.) fruit is a horticultural product consumed worldwide that has great nutritional and economic relevance. Besides the phenotypical changes that pepper fruit undergoes during ripening, there are many associated modifications at transcriptomic, proteome, biochemical and metabolic levels. Nitric oxide (NO) is a recognized signal molecule with regulatory functions in diverse plant processes. To our knowledge, there is very scarce information about the number of genes encoding for NADP-ME in pepper plants and their expression during the ripening of sweet pepper fruit. Using a data mining approach to evaluate the pepper plant genome and fruit transcriptome (RNA-seq), five NADP-ME genes were identified, and four of them, namely CaNADP-ME2 to CaNADP-ME5, were expressed in fruit. The time course expression analysis of these genes during different fruit ripening stages, including green immature (G), breaking point (BP) and red ripe (R), showed that they were differentially modulated. Thus, while CaNADP-ME3 and CaNADP-ME5 were upregulated, CaNADP-ME2 and CaNADP-ME4 were downregulated. Exogenous NO treatment of fruit triggered the downregulation of CaNADP-ME4. We obtained a 50-75% ammonium-sulfate-enriched protein fraction containing CaNADP-ME enzyme activity, and this was assayed via non-denaturing polyacrylamide gel electrophoresis (PAGE). The results allow us to identify four isozymes designated from CaNADP-ME I to CaNADP-ME IV. Taken together, the data provide new pieces of information on the CaNADP-ME system with the identification of five CaNADP-ME genes and how the four genes expressed in pepper fruits are modulated during ripening and exogenous NO gas treatment.

Functions of Melatonin during Postharvest of Horticultural Crops

Melatonin, a tryptophan-derived molecule, is endogenously generated in animal, plant, fungal and prokaryotic cells. Given its antioxidant properties, it is involved in a myriad of signaling functions associated with various aspects of plant growth and development. In higher plants, melatonin (Mel) interacts with plant regulators such as phytohormones, as well as reactive oxygen and nitrogen species including hydrogen peroxide (H2O2), nitric oxide (NO) and hydrogen sulfide (H2S). It shows great potential as a biotechnological tool to alleviate biotic and abiotic stress, to delay senescence and to conserve the sensory and nutritional quality of postharvest horticultural products which are of considerable economic importance worldwide. This review provides a comprehensive overview of the biochemistry of Mel, whose endogenous induction and exogenous application can play an important biotechnological role in enhancing the marketability and hence earnings from postharvest horticultural crops.

The Effect of Sodium Nitroprusside Treatment on Storage Ability of Fresh-Cut Potato

Quality deterioration is a major problem restricting the fresh-cut potato industry. The present study investigated the effect of sodium nitroprusside (SNP) treatment on the quality of fresh-cut potatoes during short-term storage. The treatment was carried out immediately either before or after cutting, using an SNP concentration of 200 μmol/L. The results showed that SNP treatment inhibited the accumulation of malondialdehyde (MDA) and total soluble solids (TSSs). SNP treatment also decreased the firmness, chewing properties, and ascorbic acid (AsA) content in potatoes, maintaining high levels of total phenols (TPs), total flavonoids (TFs), nitric oxide (NO), and superoxide dismutase (SOD). Furthermore, SNP treatment restrained the rise of phenylalanine ammonia-lyase (PAL), peroxidase (POD), and polyphenol oxidase (PPO), as well as the electrolyte leakage (EL) rate. After SNP treatment, the nitrite content in the potatoes was within security scope. Comparing potatoes treated before and after cutting, the best result was noted in the potatoes soaked in SNP before cutting, which displayed the smallest losses in firmness (11.24%), chewing properties (34.30%), and AsA (40.35%), and maximum increases in TPs (32.84%), TFs (2.83-time), NO (76.11%), and SOD activity (93.15%). Moreover, this group presented the minimum MDA content, EL rate, and TSS values and the lowest PAL, POD, and PPO activities. These results indicated that 200 μmol/L SNP applied for 20 min, particularly before cutting, is an efficient alternative technology that can be used in the fresh-cut potato industry.

Interactions of melatonin, reactive oxygen species, and nitric oxide during fruit ripening: an update and prospective view

Fruit ripening is a physiological process that involves a complex network of signaling molecules that act as switches to activate or deactivate certain metabolic pathways at different levels, not only by regulating gene and protein expression but also through post-translational modifications of the involved proteins. Ethylene is the distinctive molecule that regulates the ripening of fruits, which can be classified as climacteric or non-climacteric according to whether or not, respectively, they are dependent on this phytohormone. However, in recent years it has been found that other molecules with signaling potential also exert regulatory roles, not only individually but also as a result of interactions among them. These observations imply the existence of mutual and hierarchical regulations that sometimes make it difficult to identify the initial triggering event. Among these 'new' molecules, hydrogen peroxide, nitric oxide, and melatonin have been highlighted as prominent. This review provides a comprehensive outline of the relevance of these molecules in the fruit ripening process and the complex network of the known interactions among them.

γ-Aminobutyrate Improves the Postharvest Marketability of Horticultural Commodities: Advances and Prospects

Postharvest deterioration can result in qualitative and quantitative changes in the marketability of horticultural commodities, as well as considerable economic loss to the industry. Low temperature and controlled atmosphere conditions (low O2 and elevated CO2) are extensively employed to prolong the postharvest life of these commodities. Nevertheless, they may suffer from chilling injury and other physiological disorders, as well as excessive water loss and bacterial/fungal decay. Research on the postharvest physiological, biochemical, and molecular responses of horticultural commodities indicates that low temperature/controlled atmosphere storage is associated with the promotion of γ-aminobutyrate (GABA) pathway activity, with or without the accumulation of GABA, delaying senescence, preserving quality and ameliorating chilling injury. Regardless of whether apple fruits are stored under low temperature/controlled atmosphere conditions or room temperature, elevated endogenous GABA or exogenous GABA maintains their quality by stimulating the activity of the GABA shunt (glutamate GABA succinic semialdehyde succinate) and the synthesis of malate, and delaying fruit ripening. This outcome is associated with changes in the genetic and biochemical regulation of key GABA pathway reactions. Flux estimates suggest that the GABA pool is derived primarily from glutamate, rather than polyamines, and that succinic semialdehyde is converted mainly to succinate, rather than γ-hydroxybutyrate. Exogenous GABA is a promising strategy for promoting the level of endogenous GABA and the activity of the GABA shunt in both intact and fresh-cut commodities, which increases carbon flux through respiratory pathways, restores or partially restores redox and energy levels, and improves postharvest marketability. The precise mechanisms whereby GABA interacts with other signaling molecules such as Ca2+, H2O2, polyamines, salicylic acid, nitric oxide and melatonin, or with phytohormones such as ethylene, abscisic acid and auxin remain unknown. The occurrence of the aluminum-activated malate transporter and the glutamate/aspartate/GABA exchanger in the tonoplast, respectively, offers prospects for reducing transpirational water in cut flowers and immature green fruit, and for altering the development, flavor and biotic resistance of apple fruits.

Nutraceutical Role of Polyphenols and Triterpenes Present in the Extracts of Fruits and Leaves of Olea europaea as Antioxidants, Anti-Infectives and Anticancer Agents on Healthy Growth

There is currently a worldwide consensus and recognition of the undoubted health benefits of the so-called Mediterranean diet, with its intake being associated with a lower risk of mortality. The most important characteristics of this type of diet are based on the consumption of significant amounts of fruit, vegetables, legumes, and nuts, which provide, in addition to some active ingredients, fiber and a proportion of vegetable protein, together with extra virgin olive oil (EVOO) as the main sources of vegetable fat. Fish and meat from poultry and other small farm animals are the main sources of protein. One of the main components, as already mentioned, is EVOO, which is rich in monounsaturated fatty acids and to a lesser extent in polyunsaturated fatty acids. The intake of this type of nutrient also provides an important set of phytochemicals whose health potential is widely spread and agreed upon. These phytochemicals include significant amounts of anthocyanins, stilbenes, flavonoids, phenolic acids, and terpenes of varying complexities. Therefore, the inclusion in the diet of this type of molecules, with a proven healthy effect, provides an unquestionable preventive and/or curative activity on an important group of pathologies related to cardiovascular, infectious, and cancerous diseases, as well as those related to the metabolic syndrome. The aim of this review is therefore to shed light on the nutraceutical role of two of the main phytochemicals present in Olea europaea fruit and leaf extracts, polyphenols, and triterpenes, on healthy animal growth. Their immunomodulatory, anti-infective, antioxidant, anti-aging, and anti-carcinogenic capabilities show them to be potential nutraceuticals, providing healthy growth.

Potassium (K+) Starvation-Induced Oxidative Stress Triggers a General Boost of Antioxidant and NADPH-Generating Systems in the Halophyte Cakile maritima

Potassium (K+) is an essential macro-element for plant growth and development given its implication in major processes such as photosynthesis, osmoregulation, protein synthesis, and enzyme function. Using 30-day-old Cakile maritima plants as halophyte model grown under K+ deprivation for 15 days, it was analyzed at the biochemical level to determine the metabolism of reactive oxygen species (ROS), key photorespiratory enzymes, and the main NADPH-generating systems. K+ starvation-induced oxidative stress was noticed by high malondialdehyde (MDA) content associated with an increase of superoxide radical (O2•−) in leaves from K+-deficient plants. K+ shortage led to an overall increase in the activity of hydroxypyruvate reductase (HPR) and glycolate oxidase (GOX), as well as of antioxidant enzymes catalase (CAT), those of the ascorbate-glutathione cycle, peroxidase (POX), and superoxide dismutase (SOD), and the main enzymes involved in the NADPH generation in both leaves and roots. Especially remarkable was the induction of up to seven CuZn-SOD isozymes in leaves due to K+ deficiency. As a whole, data show that the K+ starvation has associated oxidative stress that boosts a biochemical response leading to a general increase of the antioxidant and NADPH-generating systems that allow the survival of the halophyte Cakile maritima.

Effects of Erythrodiol on the Antioxidant Response and Proteome of HepG2 Cells

Erythrodiol (EO) is a pentacyclic triterpenic alcohol found in olive tree leaves and olive oil, and it has important effects on the health properties and quality of olive oil. In this study, we characterized the cytotoxic effects of EO on human hepatocarcinoma (HepG2) cells by studying changes in cell viability, reactive oxygen species (ROS) production, antioxidant defense systems, and the proteome. The results reveal that EO markedly decreased HepG2 cell viability without changing ROS levels. The concentrations of glutathione and NADPH were significantly reduced, with selective changes in the activity of several antioxidant enzymes: glutathione peroxidase, glutathione reductase, glucose 6-phosphate dehydrogenase, and 6-phosphogluconate dehydrogenase. Proteomic data reveal that EO led to the complete elimination or decreased abundance of 41 and 3 proteins, respectively, and the abundance of 29 proteins increased. The results of functional enrichment analysis show that important metabolic processes and the nuclear transport of mature mRNA were impaired, whereas AMP biosynthesis and cell cycle G2/M phase transition were induced. The transcription factors and miRNAs involved in this response were also identified. These potent antiproliferative effects make EO a good candidate for the further analysis of its hepatic antitumor effects in in vivo studies.

Shining a light on NAD- and NADP-based metabolism in plants

The pyridine nucleotides nicotinamide adenine dinucleotide [NAD(H)] and nicotinamide adenine dinucleotide phosphate [NADP(H)] simultaneously act as energy transducers, signalling molecules, and redox couples. Recent research into photosynthetic optimisation, photorespiration, immunity, hypoxia/oxygen signalling, development, and post-harvest metabolism have all identified pyridine nucleotides as key metabolites. Further understanding will require accurate description of NAD(P)(H) metabolism, and genetically encoded fluorescent biosensors have recently become available for this purpose. Although these biosensors have begun to provide novel biological insights, their limitations must be considered and the information they provide appropriately interpreted. We provide a framework for understanding NAD(P)(H) metabolism and explore what fluorescent biosensors can, and cannot, tell us about plant biology, looking ahead to the pressing questions that could be answered with further development of these tools.

Loss of function of the chloroplast membrane K+/H+ antiporters AtKEA1 and AtKEA2 alters the ROS and NO metabolism but promotes drought stress resilience

Potassium (K⁺) exerts key physiological functions such as osmoregulation, stomatal movement, membrane transport, protein synthesis and photosynthesis among others. Previously, it was demonstrated in Arabidopsis thaliana that the loss of function of the chloroplast K⁺Efflux Antiporters KEA1 and KEA2, located in the inner envelope membrane, provokes inefficient photosynthesis. Therefore, the main goal of this study was to evaluate the potential impact of the loss of function of those cation transport systems in the metabolism of reactive oxygen and nitrogen species (ROS and RNS). Using 14-day-old seedlings from Arabidopsis double knock-out kea1kea2 mutants, ROS metabolism and NO content in roots and green cotyledons were studied at the biochemical level. The loss of function of AtKEA1 and AtKEA2 did not cause oxidative stress but it provoked an alteration of the ROS homeostasis affecting some ROS-generating enzymes. These included glycolate oxidase (GOX) and NADPH-dependent superoxide generation activity, enzymatic and non-enzymatic antioxidants and both NADP-isocitrate dehydrogenase and NADP-malic enzyme activities. NO content, analyzed by confocal laser scanning microscopy (CLSM), was negatively affected in both photosynthetic and non-photosynthetic organs in kea1kea2 mutant seedlings. Furthermore, the S-nitrosoglutathione reductase (GSNOR) protein expression and activity were downregulated in kea1kea2 mutants, whereas the tyrosine nitrated protein profile, analyzed by immunoblot, was unaffected but the relative expression of each immunoreactive band changed. Moreover, kea1kea2 mutants showed an increased photorespiratory pathway and stomata closure, thus promoting a higher resilience to drought stress. Data suggest that the chloroplast osmotic balance and integrity maintained by AtKEA1 and AtKEA2 are necessary to keep the balance of ROS/RNS metabolism. Moreover, these data open new questions about how endogenous NO generation might be affected by the K⁺/H⁺ transport located in the chloroplasts.

Nitric oxide and hydrogen sulfide modulate the NADPH-generating enzymatic system in higher plants

Nitric oxide (NO) and hydrogen sulfide (H2S) are two key molecules in plant cells that participate, directly or indirectly, as regulators of protein functions through derived post-translational modifications, mainly tyrosine nitration, S-nitrosation, and persulfidation. These post-translational modifications allow the participation of both NO and H2S signal molecules in a wide range of cellular processes either physiological or under stressful circumstances. NADPH participates in cellular redox status and it is a key cofactor necessary for cell growth and development. It is involved in significant biochemical routes such as fatty acid, carotenoid and proline biosynthesis, and the shikimate pathway, as well as in cellular detoxification processes including the ascorbate-glutathione cycle, the NADPH-dependent thioredoxin reductase (NTR), or the superoxide-generating NADPH oxidase. Plant cells have diverse mechanisms to generate NADPH by a group of NADP-dependent oxidoreductases including ferredoxin-NADP reductase (FNR), NADP-glyceraldehyde-3-phosphate dehydrogenase (NADP-GAPDH), NADP-dependent malic enzyme (NADP-ME), NADP-dependent isocitrate dehydrogenase (NADP-ICDH), and both enzymes of the oxidative pentose phosphate pathway, designated as glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH). These enzymes consist of different isozymes located in diverse subcellular compartments (chloroplasts, cytosol, mitochondria, and peroxisomes) which contribute to the NAPDH cellular pool. We provide a comprehensive overview of how post-translational modifications promoted by NO (tyrosine nitration and S-nitrosation), H2S (persulfidation), and glutathione (glutathionylation), affect the cellular redox status through regulation of the NADP-dependent dehydrogenases.

Sodium Nitroprusside Functions in Browning Control and Quality Maintaining of Postharvest Rambutan Fruit

Surface browning after harvest is the primary constraint affecting the storage life and market circulation of rambutans. In this study, rambutan fruits were soaked in sodium nitroprusside at different concentrations and stored at 25°C for 8 days to explore the effects on postharvest quality and browning. The weight loss, browning index and superoxide anion radical, hydrogen peroxide and malondialdehyde contents of the treated fruits were reduced compared to those of the control fruits (soaked in distilled water). And fruits treated with sodium nitroprusside had a higher total phenolic content and lower polyphenol oxidase and peroxidase activity. In addition, compared with the control, the treated fruits exhibited higher phenylalanine ammonia lyase, ascorbate peroxidase and superoxide dismutase activities; titratable acidity; and soluble solid, vitamin C and protein contents, indicating high fruit quality. Overall, sodium nitroprusside treatment at 200 μmol L^-1 demonstrated the most positive preservation effects. Therefore, sodium nitroprusside treatment, particularly at 200 μmol L^-1, can be used as an eco-friendly, safe and convenient method for postharvest quality management and high-efficiency preservation of rambutan fruits.

Nitric oxide: A radical molecule with potential biotechnological applications in fruit ripening

Nitric oxide (NO) is a short-life and free radical molecule involved in a wide range of cellular, physiological and stressful processes in higher plants. In recent years it has been observed that exogenous NO application can palliate adverse damages against abiotic and biotic stresses. Conversely, there is accumulating information indicating that endogenous NO participates significantly in the mechanism of modulation of the ripening in climacteric and non-climacteric fruits. Even more, when NO is exogenously applied, it can mediate beneficial effects during ripening and postharvest storage being one of the main effects the increase of antioxidant systems. Consequently, NO could be a promising biotechnological tool to improve crops through ameliorating nutritional indexes and to alleviate damages during fruit ripening and postharvest management. Thus, this approach should be complementary to previous strategies to allow preserving the quality and healthiness of fruits with a view of enhancing their added value. The present mini-review aims to provide an overview of NO biochemistry in plants and updated information on the relevance of NO in fruit ripening and postharvest stages with a view to its biotechnological applications.

Appraisal of H2S metabolism in Arabidopsis thaliana: In silico analysis at the subcellular level

Hydrogen sulfide (H₂S) has become a new signal molecule in higher plants which seems to be involved in almost all physiological processes from seed germination, root and plant growth until flowering and fruit ripening. Moreover, H₂S also participates in the mechanism of response against adverse environmental stresses. However, its basic biochemistry in plant cells can be considered in a nascent stage. Using the available information of the model plant Arabidopsis thaliana, the goal of the present study is to provide a broad overview of H₂S metabolism and to display an in silico analysis of the 26 enzymatic components involved in the metabolism of H₂S and their subcellular compartmentation (cytosol, chloroplast and mitochondrion) thus providing a wide picture of the cross-talk inside the organelles and amongst them and, consequently, to get a better understanding of the cellular and tissue implications of H₂S. This information will be also relevant for other crop species, especially those whose whole genome is not yet available.

Antioxidant Profile of Pepper (Capsicum annuum L.) Fruits Containing Diverse Levels of Capsaicinoids

Capsicum is the genus where a number of species and varieties have pungent features due to the exclusive content of capsaicinoids such as capsaicin and dihydrocapsaicin. In this work, the main enzymatic and non-enzymatic systems in pepper fruits from four varieties with different pungent capacity have been investigated at two ripening stages. Thus, a sweet pepper variety (Melchor) from California-type fruits and three autochthonous Spanish varieties which have different pungency levels were used, including Piquillo, Padrón and Alegría riojana. The capsaicinoids contents were determined in the pericarp and placenta from fruits, showing that these phenyl-propanoids were mainly localized in placenta. The activity profiles of catalase, total and isoenzymatic superoxide dismutase (SOD), the enzymes of the ascorbate–glutathione cycle (AGC) and four NADP-dehydrogenases indicate that some interaction with capsaicinoid metabolism seems to occur. Among the results obtained on enzymatic antioxidants, the role of Fe-SOD and the glutathione reductase from the AGC is highlighted. Additionally, it was found that ascorbate and glutathione contents were higher in those pepper fruits which displayed the greater contents of capsaicinoids. Taken together, all these data indicate that antioxidants may contribute to preserve capsaicinoids metabolism to maintain their functionality in a framework where NADPH is perhaps playing an essential role.

Exogenous phytosulfokine α (PSKα) applying delays senescence and relief decay in strawberry fruits during cold storage by sufficient intracellular ATP and NADPH availability

Herein, we employed exogenous phytosulfokine α (PSKα) for delaying senescence and lessening decay in strawberry fruits during storage at 4 °C for 18 days. Our results showed that the strawberry fruits treated with 150 nM PSKα exhibited lower expression of poly-ADP-ribose polymerase 1 (PARP1) gene, leading to a higher intracellular NAD⁺ availability, beneficial for a sufficient provision of intracellular NADP⁺ with the activity of NAD kinase (NADK). Moreover, higher activities of glucose 6-phosphate dehydrogenase (G6PDH), 6-phosphogluconate dehydrogenase (6PGDH), and methylenetetrahydrofolate dehydrogenase (MTHFD) may be the reason for the sufficient intracellular availability of NADPH in strawberry fruits treated with 150 nM PSKα. In addition, strawberry fruits treated with 150 nM PSKα exhibited a sufficient availability of ATP resulted from higher activities of succinate dehydrogenase (SDH) and cytochrome c oxidase (CCO). Therefore, our results indicate that exogenous PSKα could be beneficial for delaying senescence and reducing decay in strawberry fruits during cold storage.