Exogenous Application of Proline and L-Cysteine Alleviates Internal Browning and Maintains Eating Quality of Cold Stored Flat ‘Maleki’ Peach Fruits

Proline inhibits postharvest physiological deterioration of cassava by improving antioxidant capacity

Cassava (Manihot esculenta Crantz), a crucial global tuber crop, encounters significant economic losses attributed to postharvest physiological deterioration (PPD). The PPD phenomenon in cassava is closely related to the accumulation of reactive oxygen species (ROS), and amino acids play a pivotal role in regulating signaling pathways and eliminating ROS. In this study, the storage performance of eight cassava varieties were conducted. Cassava cultivar SC5 showed the best storage performance among the eight cassava varieties, but the edible cassava cultivar SC9 performed much worse. Comparative analysis of free amino acids was conducted in eight cassava varieties, revealing changes in proline, aspartic acid, histidine, glutamic acid, threonine, and serine. Exogenous supplementation of these six amino acids was performed to inhibit PPD of SC9. Proline was confirmed as the key amino acid for inhibiting PPD. Treatment with optimal exogenous proline of 5 g/L resulted in a 17.9% decrease in the deterioration rate compared to untreated cassava. Accompanied by a decrease in H2O2 content and an increase in catalase, superoxide dismutase and ascorbate peroxidase activity. Proline treatment proved to be an effective approach to alleviate cell oxidative damage, inhibit PPD in cassava, and prolong shelf life.

Enhancing Postharvest Quality and Shelf Life of Strawberries through Advanced Coating Technologies: A Comprehensive Investigation of Chitosan and Glycine Betaine Nanoparticle Treatments

The application of natural polymer-based coatings presents a viable approach to prolong the longevity of fruits and tissue damage. This study investigates the impact of treatments involving glycine betaine (GB), chitosan (CTS), and chitosan-coated glycine betaine nanoparticles (CTS-GB NPs) on preserving the quality and reducing decay in strawberry fruits. The fruits were subjected to treatments with GB (1 mM), CTS (0.1%), CTS-GB NPs (0.1%), or distilled water at 20 °C for 5 min, followed by storage at 4 °C for 12 days. The results indicate that CTS and CTS-GB NPs treatments resulted in the highest tissue firmness, total anthocyanin content, and ascorbate peroxidase activity, while exhibiting the lowest decay percentage and weight loss, as well as reduced malondialdehyde levels at the end of storage. GB, CTS, and CTS-GB NPs treatments demonstrated elevated catalase activity and antioxidant capacity, coupled with lower electrolyte leakage and hydrogen peroxide levels. These treatments did not significantly differ from each other but were markedly different from the control. The results substantiate that CTS and CTS-GB NPs treatments effectively preserve strawberry quality and extend storage life by bolstering antioxidant capacity and mitigating free radical damage.

Comprehensive insight into an amino acid metabolic network in postharvest horticultural products: a review

Amino acid (AA) metabolism plays a vital role in the central metabolism of plants. In addition to protein biosynthesis, AAs are involved in secondary metabolite biosynthesis, signal transduction, stress response, defense against pathogens, flavor formation, and so on. Besides these functions, AAs can be degraded into precursors or intermediates of the tricarboxylic acid cycle to substitute respiratory substrates and restore energy homeostasis, as well as directly acting as signal molecules or be involved in the regulation of plant signals to delay senescence of postharvest horticultural products (PHPs). AA metabolism and its role in plants growth have been clarified; however, only a few studies about their roles exist concerning the postharvest preservation of fruit and vegetables. This study reviews the potential functions of various AAs by comparing the difference in AA metabolism at the postharvest stage and then discusses the crosstalk of AA metabolism and energy metabolism, the target of rapamycin/sucrose nonfermenting-related kinase 1 signaling and secondary metabolism. Finally, the roles and effect mechanism of several exogenous AAs in the preservation of PHPs are highlighted. This review provides a comprehensive insight into the AA metabolism network in PHPs. © 2023 Society of Chemical Industry.

Assessment of proline function in higher plants under extreme temperatures

Climate change and abiotic stress factors are key players in crop losses worldwide. Among which, extreme temperatures (heat and cold) disturb plant growth and development, reduce productivity and, in severe cases, lead to plant death. Plants have developed numerous strategies to mitigate the detrimental impact of temperature stress. Exposure to stress leads to the accumulation of various metabolites, e.g. sugars, sugar alcohols, organic acids and amino acids. Plants accumulate the amino acid 'proline' in response to several abiotic stresses, including temperature stress. Proline abundance may result from de novo synthesis, hydrolysis of proteins, reduced utilization or degradation. Proline also leads to stress tolerance by maintaining the osmotic balance (still controversial), cell turgidity and indirectly modulating metabolism of reactive oxygen species. Furthermore, the crosstalk of proline with other osmoprotectants and signalling molecules, e.g. glycine betaine, abscisic acid, nitric oxide, hydrogen sulfide, soluble sugars, helps to strengthen protective mechanisms in stressful environments. Development of less temperature-responsive cultivars can be achieved by manipulating the biosynthesis of proline through genetic engineering. This review presents an overview of plant responses to extreme temperatures and an outline of proline metabolism under such temperatures. The exogenous application of proline as a protective molecule under extreme temperatures is also presented. Proline crosstalk and interaction with other molecules is also discussed. Finally, the potential of genetic engineering of proline-related genes is explained to develop 'temperature-smart' plants. In short, exogenous application of proline and genetic engineering of proline genes promise ways forward for developing 'temperature-smart' future crop plants.

l-Cysteine Treatment Delayed the Quality Deterioration of Fresh-Cut Button Mushrooms by Regulating Oxygen Metabolism, Inhibiting Water Loss, and Stimulating Endogenous H2S Production

Although fresh-cut button mushrooms are popular with consumers, quality deterioration presents a significant shelf-life challenge. In this study, fresh-cut button mushrooms were treated with 0.25 g/L l-cysteine (l-Cys) and evaluated in terms of quality, physiology, and transcriptome sequencing. The results indicated that l-Cys application significantly delayed the browning degree of fresh-cut button mushrooms and reduced weight loss. l-Cys treatment reduced the malondialdehyde content, lipoxygenase activity, and reducing sugar levels while enhancing the soluble protein and total phenolic content. Furthermore, l-Cys treatment reduced the O₂^- generation rate and H₂O₂ accumulation while enhancing the catalase activity. Moreover, l-Cys improved the superoxide dismutase, glutathione reductase, and phenylalanine ammonia-lyase activities while reducing those of polyphenol oxidase and peroxidase. Additionally, l-Cys treatment increased endogenous H₂S production and AbCBS enzyme activity while decreasing AbCSE enzyme activity. Notably, additional treatment with 1 mM propargylglycine significantly reduced the effect of l-Cys. Moreover, transcriptome sequencing analysis indicated that the differentially expressed genes in the l-Cys group were primarily related to the reactive oxygen species metabolism, oxidoreductase process, membrane integrality, and sulfur metabolism. These findings suggested that l-Cys treatment delayed the aging and extended the shelf life of fresh-cut button mushrooms by regulating the active oxygen species metabolism and water loss and stimulating endogenous H₂S production.

Melatonin triggers tissue-specific changes in anthocyanin and hormonal contents during postharvest decay of Angeleno plums

Plum is a stone fruit that stands out for having a short shelf-life because of its high susceptibility to rapid deterioration. Part of this deterioration is explained by fruit overripening. Recently, the role of melatonin in delaying postharvest decay has been investigated but its regulatory function during overripening is still under extensive debate. In this study, to understand physiological events taking place in plums overripening and elucidate the role of melatonin on the postharvest quality of these fruits and its relationship to other plant hormones, Angeleno plums were sprayed with 10^-4 M of melatonin solution immediately after harvest. We carried out tissue-specific (mesocarp and exocarp) analysis of total phenols and anthocyanin quantification, as well as the evaluation of different phytohormones by LC-MS/MS and fruit quality parameters. Results showed that during postharvest, endogenous melatonin contents decreased both in the mesocarp and the exocarp of Angeleno plums. Likewise, plum firmness also decreased and a strong correlation was found for this parameter with jasmonic acid (JA) and cytokinins. Conversely, after exogenous melatonin application, endogenous melatonin content increased both in mesocarp and exocarp but it had a differential effect depending on the plum tissue. Indeed, total phenol and anthocyanin contents arose by 21% and 58%, respectively, in the mesocarp after melatonin treatment but no variations were found in the exocarp of Angeleno plums. Hormonal analysis of Angeleno mesocarp also revealed an increase in the JA and its precursor, 12-oxo-phytodienoic acid (OPDA), on the fourth day after melatonin application as well as a positive correlation between melatonin and gibberellin 1 (GA₁). These results suggest that melatonin may be acting as a signal molecule increasing phenolic compounds contents through direct regulation and by signaling with other phytohormones. Therefore, this research provides valuable information for understanding the regulatory role of melatonin and its relationship with plant hormones during overripening to contribute to improve the postharvest quality of plums.

How to Cope with the Challenges of Environmental Stresses in the Era of Global Climate Change: An Update on ROS Stave off in Plants

With the advent of human civilization and anthropogenic activities in the shade of urbanization and global climate change, plants are exposed to a complex set of abiotic stresses. These stresses affect plants’ growth, development, and yield and cause enormous crop losses worldwide. In this alarming scenario of global climate conditions, plants respond to such stresses through a highly balanced and finely tuned interaction between signaling molecules. The abiotic stresses initiate the quick release of reactive oxygen species (ROS) as toxic by-products of altered aerobic metabolism during different stress conditions at the cellular level. ROS includes both free oxygen radicals {superoxide (O₂^•−) and hydroxyl (OH⁻)} as well as non-radicals [hydrogen peroxide (H₂O₂) and singlet oxygen (¹O₂)]. ROS can be generated and scavenged in different cell organelles and cytoplasm depending on the type of stimulus. At high concentrations, ROS cause lipid peroxidation, DNA damage, protein oxidation, and necrosis, but at low to moderate concentrations, they play a crucial role as secondary messengers in intracellular signaling cascades. Because of their concentration-dependent dual role, a huge number of molecules tightly control the level of ROS in cells. The plants have evolved antioxidants and scavenging machinery equipped with different enzymes to maintain the equilibrium between the production and detoxification of ROS generated during stress. In this present article, we have focused on current insights on generation and scavenging of ROS during abiotic stresses. Moreover, the article will act as a knowledge base for new and pivotal studies on ROS generation and scavenging.