Modulation of Actinidia arguta fruit ripening by three ethylene biosynthesis inhibitors

The AaERF64-AaTPPA module participates in cold acclimatization of Actinidia arguta (Sieb. et Zucc.) Planch ex Miq

Actinidia arguta (A. arguta, kiwiberry) is a perennial deciduous vine with a strong overwintering ability. We hypothesized that trehalose metabolism, which plays a pivotal role in the stress tolerance of plants, may be involved in the cold acclimatization of A. arguta. Transcriptome analysis showed that the expression of AaTPPA, which encodes a trehalose-6-phosphate phosphatase (TPP), was upregulated in response to low temperatures. AaTPPA expression levels were much higher in lateral buds, roots, and stem cambia than in leaves in autumn. In AaTPPA-overexpressing (OE) Arabidopsis thaliana (A. thaliana), trehalose levels were 8-11 times higher than that of the wild type (WT) and showed different phenotypic characteristics from WT and OtsB (Escherichia coli TPP) overexpressing lines. AaTPPA-OE A. thaliana exhibited significantly higher freezing tolerance than WT and OtsB-OE lines. Transient overexpression of AaTPPA in A. arguta leaves increased the scavenging ability of reactive oxygen species (ROS) and the soluble sugar and proline contents. AaERF64, an ethylene-responsive transcription factor, was induced by ethylene treatment and bound to the GCC-box of the AaTPPA promoter to activate its expression. AaTPPA expression was also induced by abscisic acid. In summary, the temperature decrease in autumn is likely to induce AaERF64 expression through an ethylene-dependent pathway, which consequently upregulates AaTPPA expression, leading to the accumulation of osmotic protectants such as soluble sugars and proline in the overwintering tissues of A. arguta.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11032-024-01475-8.

1-Methylcyclopropene treatment delays the softening of Actinidia arguta fruit by reducing cell wall degradation and modulating carbohydrate metabolism

The rapid softening of hardy kiwifruit (Actinidia arguta) fruit significantly reduces its marketing potential. Therefore, the effect of 1-methylcyclopropene (1-MCP) on the softening of A. arguta fruit was investigated. Results indicated that A. arguta fruit treated with 1-MCP maintained a higher level of firmness, titratable acidity, ascorbic acid, total phenolics, and flavonoids content, relative to non-treated fruit. Fruit treated with 1-MCP and placed in long-term cold storage had higher sensory scores, as determined by a taste panel and supported by electronic nose and tongue data. Notably, 1-MCP delayed the degradation of cell wall components, including pectin, cellulose, and hemicellulose, by reducing the activity of cell-wall-modifying enzymes. In addition, 1-MCP reduced the activity of carbohydrate metabolism-related enzymes, resulting in fruit with higher levels of starch and sucrose and lower levels of glucose, fructose and sorbitol. Collectively, these results indicate that 1-MCP can be used to delay the softening of A. arguta fruit and extend its storage and shelf life.

Nutritional Values of Minikiwi Fruit (Actinidia arguta) after Storage: Comparison between DCA New Technology and ULO and CA

The dietary properties of minikiwi make them, along with other fruits and vegetables, suitable as the basis for many slimming and pro-health diets. Prolonging the availability of minikiwi can be provided by different storage technologies. This experiment focused on evaluating the effect of various O₂ and CO₂ concentrations, i.e., low-oxygen atmosphere (DCA, 0.4% CO₂:0.4% O₂; ULO, 1.5% CO₂:1.5% O₂) or high-CO₂ (CA, 5% CO₂:1.5% O₂) storage, in order to provide the consumer with fruits with comparable high nutritional values. Evaluation gave the basic characteristics of the fruits that characterize their health-promoting properties, i.e., total polyphenols (TPC), phenolic acids and flavonols, antioxidant activity (AA), monosaccharides, and acid content. The atmosphere with a higher CO₂ content of 5% (CA) effectively influenced the high value of ascorbic acid even after 12 weeks of storage. DCA technology contributed to a significant inhibition of phenol loss but not as effectively as CA technology. In contrast, glucose and fructose contents were found to be significantly higher after storage in ULO or DCA, while sucrose content was more stable in fruit stored in CA or DCA. CA technology conditions stabilized the citric acid content of minikiwi, while DCA technology was less effective in inhibiting acid loss. The nutritional value of the fruit after storage in CA or DCA was not significantly reduced, which will allow the supply of fresh minikiwi fruit to be extended and provide a valuable component of the human diet.

Development and characterization of aldehyde-sensitive cellulose/chitosan/beeswax colorimetric papers for monitoring kiwifruit maturity

In this study, we developed an in-package colorimetric paper to monitor the ripeness of kiwifruit by detecting the release of aldehydes. Strongly hydrophobic composite films were prepared using chitosan as the matrix and beeswax as an additive. A piece of cellulose paper containing methyl red and bromocresol violet as color indicators was heat-sealed between two hydrophobic films to protect the indicators from the effects of fruit respiration and transpiration. The nucleophilic addition reaction between aldehydes and OH^- (Cannizzaro reaction) changes the pH in the paper and triggers a color change in the indicators. As the kiwifruit ripens, the colorimetric paper changes from bluish-purple to dark red and then gradually to red. A mobile phone application was further used to measure the RGB values and link them to kiwifruit ripeness. This intelligent paper can be used for the accurate and convenient monitoring of produce in real time.

Ethylene scavengers for the preservation of fruits and vegetables: A review

The phytohormone ethylene is the main cause of postharvest spoilage of fruit and vegetables (F&V). To address the global challenge of reducing postharvest losses of F&V, effective management of ethylene is of great importance. This review summarizes the various ethylene scavengers/inhibitors and emerging technologies recently developed for the effective removal of ethylene released, paying particular attention to the ethylene scavenger/inhibitors containing catalysts to promote the in-situ oxidation of ethylene without inducing further pollution. Packing ethylene scavengers, such as zeolite, titanium dioxide and transition metals, in a small sachet has been practically used and widely reported. However, incorporating ethylene scavenger into food packaging materials or films along with the in-situ oxidation of ethylene has been rarely reviewed. The current review fills up this gap, covering the latest research progress on ethylene scavengers/inhibitors and discussion on the mechanisms of ethylene elimination and oxidation associated with F&V packaging.

1-Methylcyclopropene treatment controls ethanol accumulation associated with regulation of mitochondrial energy metabolism in kiwifruit (Actinidia deliciosa) cv. "Bruno" during storage at room temperature

In this paper, the effects of 1-methylcyclopropene (1-MCP) treatment on the ethanol accumulation and mitochondrial energy metabolism in kiwifruit (Actinidia deliciosa) cv. "Bruno" were investigated during storage at room temperature (24 ± 1°C). The results showed that 1-MCP treatment significantly reduced the ethanol accumulation, maintained higher levels of adenosine triphosphate (ATP) content and energy charge (EC), enhanced enzymes activities involved in mitochondrial energy metabolism, such as succinic dehydrogenase, cytochrome C oxidase, H⁺ -adenosine triphosphatase (H⁺ -ATPase), and Ca²⁺ -adenosine triphosphatase (Ca²⁺ -ATPase), and regulated the NADH/NAD⁺ ratio, and pyruvate to tricarboxylic acid cycle (TCA) by suppressing the glutamate-pyruvate transaminase and promoting the pyruvate dehydrogenase activity, and decarboxylation of citric acid in harvested kiwifruit. These shifts in mitochondrial energy metabolism and oxidative phosphorylation correlated the higher ATP yield and an elevated EC with lower ethanol accumulation (13.71% of those in the control fruit) under 1-MCP treatment, and reduced the susceptibility of ethanol related off-flavor disorder in kiwifruit during storage. PRACTICAL APPLICATIONS: A kiwifruit (Actinidia deliciosa) cv. "Bruno," a major cultivated kiwifruit in China, is prone to accumulate ethanol sharply after respiratory climacteric during storage. Ethanol has been accounted as a vital aroma volatile metabolite in various fruits. However, over accumulation of ethanol often leads to the development of alcohol off-flavor disorder, particularly in typical climacteric fruit such as kiwifruit. This work was aimed to maintain the flavor quality of kiwifruit cv. "Bruno" via improving the mitochondrial energy metabolism and functional TCA cycle, and limiting the ethanol accumulation under 1-MCP treatment. Thus, 1-MCP treatment could be beneficial to prevent the occurrence of alcohol off-flavor disorder along with sustainment of the flavor quality of kiwifruit cv. "Bruno" during storage at room temperature.

Evaluation of 1-methylcyclopropene (1-MCP) treatment combined with nano-packaging on quality of pleurotus eryngii

The aim of the present study was to investigate the effect of 1-methylcyclopropene (1-MCP) combined with nano-packaging on quality of pleurotus eryngii stored at 4 ± 1 °C for 12 days. Texture, respiration rate, soluble protein, soluble sugar, weight loss, soluble solid, malondialdehyde (MDA) content, polyphenol oxidase (PPO), superoxide dismutase (SOD) and catalase (CAT) activity of treated pleurotus eryngii were determined. The results suggested that 1-MCP treatment combined with nano-packaging reduce respiration rate, weight loss and MDA content, delayed the decrease of soluble protein content, and maintained soluble sugar and soluble solid content of treated pleurotus eryngii during the storage at 4 ± 1 °C compared with the untreated samples. The efficiency of the combined treatment (1-MCP + nano-packaging) was better than that of 1-MCP or nano-packaging alone. Moreover, 1-MCP plus nano-packaging treatment effectively improved SOD and CAT activities, and suppressed the increase of PPO activity in pleurotus eryngii. Therefore, present results indicated that 1-MCP plus nano-packaging treatment may be an effective technology on maintaining commercial quality and lengthening shelf life of pleurotus eryngii.

Transcriptome analysis around the onset of strawberry fruit ripening uncovers an important role of oxidative phosphorylation in ripening

Although much progress has been made towards understanding the ripening of non-climacteric fruit using the strawberry as a model plant, the defined molecular mechanisms remain unclear. Here, RNA-sequencing was performed using four cDNA libraries around the onset of ripening, and a total of 31,793 unigenes and 335 pathways were annotated including the top five pathways, which were involved in ribosome, spliceosome, protein processing, plant-pathogen interaction and plant hormone signaling, and the important DEGs related to ripening were annotated to be mainly involved in protein translation and processing, sugar metabolism, energy metabolism, phytohormones, antioxidation, pigment and softening, especially finding a decreased trend of oxidative phosphorylation during red-coloring. VIGS-mediated downregulation of the pyruvate dehydrogenase gene PDHE1α, a key gene for glycolysis-derived oxidative phosphorylation, could inhibit respiration and ATP biosynthesis, whilst promote the accumulation of sugar, ABA, ETH, and PA, ultimately accelerating the ripening. In conclusion, our results demonstrate that a set of metabolism transition occurred during green-to-white-to-red stages that are coupled with more-to-less DEGs, and the oxidative phosphorylation plays an important role in the regulation of ripening. On the basis of our results, we discuss an oxidative phosphorylation-based model underlying strawberry fruit ripening.

Inhibition of hardy kiwifruit (Actinidia aruguta) ripening by 1-methylcyclopropene during cold storage and anticancer properties of the fruit extract

Hardy kiwifruits (Actinidia arguta) were treated with 20 μl/l 1-methylcyclopropene (1-MCP) for 16 h at 10 °C and subsequently stored at 1 ± 0.5 °C. Anticancer properties of the fruit extracts were tested against five different human cancer cells. The hardy kiwifruits, without 1-MCP treatment, showed increases in both respiration and ethylene production rates during fruit storage. The 1-MCP treatment remarkably inhibited fruit ripening by reducing respiration and ethylene production. Fruits with the 1-MCP treatment could be stored for up to 5 weeks by maintaining higher fruit firmness, ascorbic acid and total phenolic contents compared to the control. The hardy kiwifruit extracts showed anti-proliferative effects to Hep3B and HeLa cells but not to HT29, HepG2 and LoVo cells. These results suggest that the application of 1-MCP at harvest effectively delayed the ripening process of the fruits, and the fruit extract had beneficial effects for the prevention of human cancer growth.