Exogenous phytosulfokine α alleviates chilling injury of loquat fruit via regulating sugar, proline, polyamine and γ-aminobutyric acid metabolisms

Ripening-stage variations in small metabolites across six banana cultivars: A metabolomic perspective

Currently, understanding of how banana cultivars differ in metabolism during ripening is limited. This study compared the pulp metabolites of six banana cultivars using NMR. Bananas with B genome were found to have higher amounts of total starch, amylose, amylopectin, and resistant starch compared to those without B genome. NMR identified 21 key metabolites distinguish these cultivars. These metabolites included four soluble sugars, three organic acids, eleven amino acids, one alcohol, one choline, and one other compound. Notably, the levels of four soluble sugars varied significantly among the cultivars. 'Gongjiao' and 'Guangfen No. 1' had a slightly sour taste due to higher levels of malate and citrate. The accumulation of eleven key amino acids differed among varieties and changed unpredictably during ripening. Other important metabolites also played a role in distinguishing six banana varieties. This research provided new insights into how metabolites were used to differentiate between banana cultivars.

Hydrogen sulfide attenuates chilling injury in loquat fruit by alleviating oxidative stress and maintaining cell membrane integrity

The effects of hydrogen sulfide (H2S) on chilling injury (CI), reactive oxygen species (ROS) metabolism, sugar metabolism, pentose phosphate pathway (PPP), and membrane lipid metabolism in loquat fruit throughout the refrigerated period were investigated in this study. The findings indicated that H2S application restrained the increase in internal browning (IB), malondialdehyde (MDA) content, and electrolyte leakage, while sustaining higher total phenolic and total flavonoid levels, and lower soluble quinone content in loquat fruit. Besides, H2S promoted antioxidant accumulation and increased antioxidant enzyme activities by the regulation of ROS metabolism, along with increasing fructose and glucose levels and reducing power by activating sugar metabolism and PPP. Furthermore, H2S treatment retarded the degradation of phospholipids and fatty acids in loquat fruit by modulating membrane lipid metabolism relevant enzyme activities. These findings indicated that H2S application mitigated CI in loquat fruit by alleviating oxidative stress and maintaining cell membrane structural integrity.

Hot air treatment alleviates chilling injury of sweet potato tuberous roots by regulating osmoregulatory substances and inducing antioxidant defense system

Sweet potato tuberous roots are susceptible to chilling injury (CI) when stored below 10 °C. In this study, we investigated the mitigating effects of hot air (HA) treatment on CI. Results showed that HA45°C-3h treatment delayed the CI and internal browning during cold storage. After HA45°C-3h treatment, the cells' structural integrity was maintained, malondialdehyde accumulation and ion leakage were inhibited. Additionally, the osmoregulatory substances, such as total soluble solids, proline were maintained, and soluble protein was enhanced. Higher activity of antioxidant enzymes including superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase, and the antioxidant substances including ascorbic acid, glutathione, total phenols, and flavonoids were observed in sweet potato tuberous roots treated by HA45°C-3h than untreated group. Our study suggested that HA45°C-3h treatment could reduce CI and maintain a better quality of sweet potato tuberous roots following cold storage.

PpERF-CRF3 selected by transcriptomic analysis plays key roles in the regulation of ABA alleviating chilling injury in peach fruit

Abscisic acid (ABA) is widely utilized to mitigate chilling injury (CI) of fruit. However, the molecular mechanism of ABA alleviates CI in peach fruit remain unclear. Herein, 10-4 M ABA treatment significantly mitigated the CI of peach fruit by reducing relative conductivity and malondialdehyde content, while increasing proline and endogenous ABA content. Transcriptomic analysis indicated that an abundant number of differentially expressed genes were altered by ABA treatment, which primarily enriched pathways such as plant hormone signal transduction, glycerophospholipid metabolism and phenylpropanoid biosynthesis. RNA-Seq results indicate that ABA modulates the transcription of genes involved in auxin, ABA and ethylene signal transduction, as well as in cell wall degradation, antioxidant, fatty acid desaturation and proline metabolism. RT-qPCR confirmed the RNA-Seq results, ABA treatment induced the transcription of proline metabolism related genes (PpP5CR2, PpP5CS, PpP5CS1) and PpERF-CRF3. Particularly noteworthy, as a nuclear protein, PpERF-CRF3 activated the expression of PpP5CR2 and PpP5CS by directly binding to their promoters and over-expression PpERF-CRF3 increased proline content and enhanced PpP5CR2 and PpP5CS expression. Overall, these findings suggest that ABA mitigates CI in peach fruit may be by mediating these pathways, and PpERF-CRF3 potentially involves this process by stimulating the expression of genes related to proline synthesis.

Hot water mobilizes the metabolism of energy, soluble sugar, cell wall, and phenolics to cope with chilling injury in postharvest snap beans

BACKGROUND

Snap beans (Phaseoulus vulgaris L.) are very sensitive to low temperature during postharvest storage. Pitting, rusting, and water-soaked patches are typical chilling injury (CI) symptoms of snap beans. The appearance of these symptoms reduces the storage quality of snap beans. The energy, soluble carbohydrates, cell wall, and phenolic metabolisms of refrigerated snap beans and their relationship to CI treated with 35 °C hot water (HW) were investigated.

RESULTS

HW treatment reduced CI index and electrolyte leakage and increased the contents of soluble solids, titratable acidity, and chlorophyll. HW treatment maintained higher activities of proton ATPase, calcium ATPase, and cytochrome c oxidase, which resulted in the accumulation of more adenosine triphosphate, adenosine diphosphate, and energy charge. The accumulation of soluble sugar induced by HW treatment was correlated with the stimulation of sucrose phosphate synthase and sucrose synthase. The prevention effect of HW treatment on the degradation of cell wall components was related to the inhibition of pectin methylesterase and cellulase. HW-induced phenol accumulation is associated with an increase in shikimate dehydrogenase, phenylalanine ammonia lyase, cinnamate-4-hydroxylase, and 4-coumarine-coenzyme A ligase, as well as a decrease in polyphenol oxidase.

CONCLUSION

The alleviating effect of HW on CI is due to its regulation of energy, soluble sugar, cell wall, and phenolic metabolism. Therefore, HW treatment may be an effective means to reduce CI of snap beans. © 2024 Society of Chemical Industry.

Identification and Characterization of Polyamine Metabolism in Citrus in Response to 'Candidatus Liberibacter asiaticus' Infection

Citrus Huanglongbing, one of the most devastating citrus diseases, is caused by 'Candidatus Liberibacter asiaticus' (CLas). Polyamines are aliphatic nitrogen-containing compounds that play important roles in disease resistance and are synthesized primarily by two pathways: an arginine decarboxylation pathway and an ornithine decarboxylation pathway. However, it is unclear whether polyamines play a role in the tolerance of citrus to infection by CLas and, if so, whether one or both of the core polyamine metabolic pathways are important. We used high-performance liquid chromatography and ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry to detect the contents of nine polyamine metabolism-related compounds in six citrus cultivars with varying levels of tolerance to CLas. We also systematically detected the changes in polyamine metabolism-related compounds and H2O2 contents and compared the gene expression levels and the activities of enzymes involved in the polyamine metabolic pathway among healthy, asymptomatic, and symptomatic leaves of Newhall navel oranges infected with CLas. The tolerant and moderately tolerant varieties showed higher polyamine metabolism-related compound levels than those of susceptible varieties. Compared with the healthy group, the symptomatic group showed significantly increased contents of arginine, ornithine, γ-aminobutyric acid, and putrescine by approximately 180, 19, 1.5, and 0.2 times, respectively, and upregulated expression of biosynthetic genes. Arginase and ornithine decarboxylase enzyme activities were the highest in the symptomatic group, whereas arginine decarboxylase and agmatine deiminase enzyme activities were the highest in the asymptomatic group. The two polyamine biosynthetic pathways showed different trends with the increase of the CLas titer, indicating that polyamines were mainly synthesized through the arginine decarboxylase pathway in the asymptomatic leaves and were synthesized via the ornithine decarboxylase pathway in symptomatic leaves. These findings provide new insight into the changes in polyamine metabolism in citrus infected with CLas.

The metabolism of amino acids, AsA and abscisic acid induced by strigolactone participates in chilling tolerance in postharvest zucchini fruit

Zucchini fruit are notably susceptible to chilling injury when stored at low temperatures. The purpose of this experimental investigation was to assess the influence of strigolactone (ST) (5 μmol L-1) on mitigating chilling injury and the metabolic changes in amino acids, ascorbic acid, and abscisic acid in zucchini fruit stored at 4°C. Research findings demonstrated that ST-treated zucchini fruit displayed a significantly higher tolerance to chilling stress compared to the control group. Postharvest ST treatment led to a decrease in weight loss, accompanied by reduced levels of malondialdehyde and relative ion leakage compared to the untreated group. ST immersion significantly boosted the metabolic pathways associated with proline and arginine, affecting both the enzymatic reactions and gene expressions, thus cumulatively increasing the internal concentrations of these amino acids in zucchini fruit. Zucchini treated with ST exhibited an increased concentration of γ-aminobutyric acid (GABA) as a result of augmented activities and elevated transcriptional levels of glutamate decarboxylase (GAD), GABA transaminase (GAT), and succinate semialdehyde dehydrogenase (SSD). In the ST-treated sample, the elevated enzymatic activities and enhanced gene expressions within the ascorbic acid (AsA) biosynthesis pathway worked together to sustain AsA accumulation. The application of ST resulted in a rise in abscisic acid (ABA) concentration, which correspondingly correlated with the induction of both activities and gene expression levels of crucial enzymes involved in ABA metabolism. Our findings revealed that submerging zucchini fruit in ST could be a highly effective strategy for boosting their chilling tolerance. The alleviation in chilling injury induced by ST may be attributed to the modulation of proline, arginine, GABA, AsA and ABA metabolism.

Effects of the Combined Treatment of Trans-2-Hexenal, Ascorbic Acid, and Dimethyl Dicarbonate on the Quality in Fresh-Cut Potatoes (Solanum tuberosum L.) during Storage

Fresh-cut potatoes (Solanum tuberosum L.) are susceptible to browning and microbial contamination during storage. In this study, the effects of trans-2-hexenal (E2H), ascorbic acid (VC), dimethyl dicarbonate (DMDC), and the combined treatment of E2H, VC, and DMDC on quality deterioration in fresh-cut potatoes were investigated. The response surface methodology (RSM) demonstrated that E2H, VC, and DMDC concentrations of 0.010%, 0.65%, and 240 mg/L, respectively, were the optimum conditions for fresh-cut potato preservation. Further analysis showed that the combined treatment of E2H, VC, and DMDC was the most effective method of reducing quality deterioration in potatoes compared to the control and individual treatments. Furthermore, the combined treatment of E2H, VC, and DMDC could decrease the accumulation of reactive oxygen species (ROS) via improving antioxidant enzyme activities. Meanwhile, energy-metabolism-related enzyme activities and glutamate decarboxylase (GAD) activity were enhanced, while γ-aminobutyric acid transaminase (GABA-T) activity was reduced via the combined treatment of E2H, VC, and DMDC, which contributed to maintaining high energy levels and GABA content in potatoes. These findings suggested that the combined treatment of E2H, VC, and DMDC could protect membrane integrity through enhancing antioxidant capacity, energy levels, and GABA content to maintain quality in fresh-cut potatoes.

Z, Cai X, Zhao X, Jiang Y, Miao B. Quality Assessment of Loquat under Different Preservation Methods Based on Physicochemical Indicators, GC–MS and Intelligent Senses

To explore the effects of different preservation methods on the quality of loquat after fresh-keeping treatment, various preservation techniques were employed. These included natural preservation (NP), vacuum freezing preservation (VFP), vacuum at room temperature preservation (VP) and freezing preservation (FP). The quality assessment involved analyzing the effects of these preservation methods using physicochemical indexes, a colorimeter, an electronic nose (E-nose), an electronic tongue (E-tongue) and gas chromatography–mass spectrometry (GC–MS). The results showed minor differences in loquat quality under different preservation methods, with sensory scores ranging from 55 to 78 and ΔE values ranging from 11.92 to 18.59. Significant variations were observed in moisture content (ranging from 53.20 g/100 g to 87.20 g/100 g), calorie content (ranging from 42.55 Kcal/100 g to 87.30 Kcal/100 g), adhesion (ranging from 0.92 to 1.84 mJ) and hardness (ranging from 2.97 to 4.19 N) (p < 0.05). Additionally, the free amino acid content varied from 22.47 mg/g to 65.42 mg/g. GC–MS analysis identified a total of 47 volatile flavor substances in varieties of loquats, including 13 aldehydes, 9 esters, 6 ketones, 2 acids, 3 alcohols, 2 phenols, 3 pyrazines, 1 furan and 8 other substances. The relative content of aldehydes was significantly higher than that of other chemicals. The VFP and FP samples exhibited higher aldehyde content compared to the NP and VP samples. Moreover, Orthogonal Partial Least Squares-Discriminant Analysis (OPLS-DA) revealed 18 marked compounds that could differentiate between 5 loquat species. Analysis using E-nose and E-tongue indicated significant changes in the olfactory and gustatory senses of loquats following preservation. The VFP samples demonstrated the most effective preservation of loquat quality with minimal impact. This study provides some theoretical guidance for the home preservation of loquats.

Effect of riboflavin on redox balance, osmolyte accumulation, methylglyoxal generation and nutrient acquisition in indian squash (Praecitrullus fistulosus L.) under chromium toxicity

The presence of high chromium (Cr) levels induces the buildup of reactive oxygen species (ROS), resulting in hindered plant development. Riboflavin (vitamin B2) is produced by plants, fungi, and microbes. It serves as a precursor to the coenzymes flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN), which play a crucial role in cellular metabolism. The objective of this work was to clarify the underlying mechanisms by which riboflavin alleviates Cr stress in Praecitrullus fistulosus L. Further, the role of riboflavin in growth, ions homeostasis, methylglyoxal detoxification, and antioxidant defense mechanism are not well documented in plants under Cr toxicity. We found greater biomass and minimal production of ROS in plants pretreated with riboflavin under Cr stress. Results manifested a clear abridge in growth, chlorophyll content, and nutrient uptake in Indian squash plants exposed to Cr stress. Findings displayed that Cr stress visibly enhanced oxidative injury reflected as higher malondialdehyde (MDA), hydrogen peroxide (H2O2), superoxide radical (O2•‒), methylglyoxal (MG) levels alongside vivid lipoxygenase activity. Riboflavin strengthened antioxidant system, enhanced osmolyte production and improved membrane integrity. Riboflavin diminished Cr accumulation in aerial parts that led to improved nutrient acquisition. Taken together, riboflavin abridged Cr phytotoxic effects by improving redox balance because plants treated with riboflavin had strong antioxidant system that carried out effective ROS detoxification. Riboflavin protected membrane integrity that, in turn, improved nutrient uptake in plants.