The effects of 10 mM γ-aminobutyric acid (GABA) treatment on fruit softening, starch degradation, cell wall disassembly in cold-stored ‘Hongyang’ kiwifruit after harvest were investigated. The ...results depicted that GABA treatment maintained firmness and delayed fruit softening during storage by retaining high starch content due to the inhibition of the transcription levels of related starch-degrading genes, such as AcGWD, AcPWD, and AcBAMs. In addition, compared with the control, higher level of chelated-soluble pectin, Na2CO3-soluble pectin, hemicellulose and cellulose content but lower water-soluble pectin content were observed in the treated kiwifruit as GABA suppressed cell wall breakdown by down-regulating the expression of AcPE, AcPG, AcBGALs, and AcXTHs. In summary, our results indicated that exogenous GABA contributes to maintaining fruit firmness, delaying softening in postharvest kiwifruit by inhibiting starch degradation and preserving cell wall metabolism.
•GABA treatment delayed fruit softening in cold-stored kiwifruit.•GABA suppressed starch-degrading gene expression to inhibit starch degradation.•GABA increased CSP, NSP, hemicellulose and cellulose but decreased WSP content.•GABA reduced cell wall breakdown by suppressing AcPE, AcPG, AcBGALs and AcXTHs.
•High O2/N2 controlled atmosphere accelerated postharvest ripening of ‘Hayward’ kiwifruit.•High O2/N2 controlled atmosphere had no adverse effect on fruit quality.•Kiwifruit ripening was closely ...associated with energy levels.•Fruit under High O2/N2 controlled atmosphere had higher expression of ripening-related genes.
Kiwifruit (Actinidia deliciosa cv. Hayward) was exposed to high O2/N2 controlled atmosphere (30 % O2 + 70 % N2) for 7 d at 23 ± 1 °C to evaluate the effects on postharvest ripening and fruit quality. The treated fruit exhibited a dramatic increase in soluble solids content (SSC) and a rapid decrease in firmness and titratable acidity (TA), accompanied by a noticeable change in flesh color and volatile organic compounds during the first 7 d. Fruit exposed to high oxygen concentration required 7 d to reach the edible firmness (∼ 10 N), while the control fruit needed 42 d. At edible firmness, no differences in the SSC, TA, and flesh color were observed between treated and untreated kiwifruit, although the concentration and amounts of volatile organic compounds showed a little difference. High O2/N2 controlled atmosphere advanced respiration rate peak, with an increase in the contents of adenosine triphosphate (ATP), adenosine diphosphate (ADP), and adenosine monophosphate (AMP). The treatment also increased catalase (CAT) and peroxidase (POD) activities. Quantitative real-time PCR revealed increased expression levels of AdAAC1, AdAOX2, AcEXP1, AcPL1, AcPG, AcACS, AcACO, and AcACO2 in the treated fruit. Thus, the study's results indicate that high O2/N2 controlled atmosphere could accelerate kiwifruit ripening and result in good fruit quality.
A high sensitivity radiofrequency (RF) passive resonator is used to investigate the feasibility of fruit ripening assessment by non-contact sensing of fruit dielectric property changes. To do so, ...kiwifruit samples of similar size and ripeness are monitored during 14 days using the RF resonator, used as an inductive sensor. The recording of the sensor impedance enables monitoring of the fruit complex dielectric permittivity changes induced by the ripening process. These results are compared to mechanical tests carried out on the kiwifruit samples during ripening, which validate the ability of the proposed RF sensor to monitor the ripening process. These preliminary results open the way to developing a low-cost, non-contact and non-destructive assessment of the fruit ripening process.
Display omitted
•A non-contact RF passive resonator is used to monitor kiwifruit ripening.•RF resonator enables the monitoring of kiwifruit complex dielectric properties.•Dielectric properties of the kiwifruit feature a monotonous increase with time.•Kiwifruit dielectric monitoring is consistent with visual observations and firmness.
Whole kiwifruit (‘Hayward’ and ‘Zesy002’) were examined for their bioaminergic potential after being subjected to in vitro gastrointestinal digestion and colonic fermentation. Controls included the ...prebiotic inulin and water, a carbohydrate-free vehicle. The dopamine precursor l-dihydroxyphenylalanine (L-DOPA) and the serotonin precursor 5-hydroxytryptophan were increased in the kiwifruit gastrointestinal digesta (‘Hayward’ > ‘Zesy002’) in comparison to the water digesta. Fermentation of the digesta with human fecal bacteria for 18 h modulated the concentrations of bioamine metabolites. The most notable were the significant increases in L-DOPA (‘Zesy002’ > ‘Hayward’) and γ-aminobutyric acid (GABA) (‘Hayward’ > ‘Zesy002’). Kiwifruit increased Bifidobacterium spp. and Veillonellaceae (correlating with L-DOPA increase), and Lachnospira spp. (correlating with GABA). The digesta and fermenta were incubated with Caco-2 cells for 3 h followed by gene expression analysis. Effects were seen on genes related to serotonin synthesis/re-uptake/conversion to melatonin, gut tight junction, inflammation and circadian rhythm with different digesta and fermenta from the four treatments. These indicate potential effects of the substrates and the microbially generated organic acid and bioamine metabolites on intestinal functions that have physiological relevance. Further studies are required to confirm the potential bioaminergic effects of gut microbiota–kiwifruit interactions.
Warm temperature exposure during winter has reportedly resulted in the apparent negation of chilling in several fruit species. This study was conducted to investigate the floral and vegetative ...response of two pistillate kiwifruit cultivars to intermittent warm temperature interruption during chilling accumulation. Dormant 1-year-old canes of Actinidia chinensis ‘AU Golden Dragon’ and Actinidia deliciosa ‘AU Fitzgerald’ were collected in December 2018 and 2019 (334 and 360 chilling units, respectively), shortly after leaf abscission. Canes were cut to 10 nodes after removing the first six basal nodes, placed in jars filled with distilled water, and transferred to respective chilling treatments. Treatments included continuous chilling (CC) (in addition to base chilling) at 1-week (168 chilling units) increments (0–5 weeks) and chilling exposure at the same increments with intermittent warm temperature (WT). For the WT treatments, each week of chilling was followed by 3 days of exposure to warm conditions. Chilling and warm temperature exposure were simulated by 7/4 °C and 25/17.2 °C (day/night) air temperatures, respectively, using separate climate-controlled growth chambers. After treatments, canes were forced in a third chamber at 21.1 to 25.0 °C with light-emitting diode lighting. Vegetative budbreak, floral bud number (from here on defined as floral response), and floral development stage were recorded for each cane at 2-day intervals. For ‘AU Golden Dragon’, WT did not result in any reduced floral response at any of the observed chilling levels. However, lower mean floral response was observed with WT, as compared with CC for ‘AU Fitzgerald’ at 5 weeks of chilling over the 2 years ( P = 0.05). WT also lessened the effect of apical dominance with respect to vegetative/floral response to node position for both cultivars. Chilling type had no significant effect on vegetative response in either cultivar. Estimated chilling requirements (CC) in this experiment were similar to those reported previously for these cultivars. Results suggest that A. chinensis cultivars may respond more favorably than A. deliciosa to the erratic winter temperature patterns experienced in the southeastern United States.
•Drought stress strongly suppressed growth, damaged cellular membranes and inhibited photosynthesis of the seedlings.•Melatonin mitigated the drought-induced growth restriction by recovering biomass ...accumulation and improving root growth.•Melatonin promoted the level of osmotica in plant cell, reduced lipid peroxidation and pigment degradation.•Melatonin improved photosynthesis by enhancing electron transport in PSII and upregulating 11 genes involved in CO2 fixation.
Melatonin is involved in regulating plant growth and responding to multiple environmental stresses. The underlying mechanism by which melatonin mediates drought tolerance in some plant species remains unknown. We investigated the effects of melatonin with different doses (50, 100, and 200 μM) on growth and photosynthesis in kiwifruit (A. chinensis var. deliciosa cv. Qinmei) seedlings under drought stress. Drought stress strongly suppressed biomass accumulation, damaged cellular membranes, and inhibited photosynthesis in the seedlings. However, irrigation with melatonin mitigated the drought-induced impairment in a dose-dependent manner, with the greatest efficiency provided by 100 μM. Melatonin promoted the development of the root system architecture, reduced lipid peroxidation and pigment degradation, alleviated injuries to cell membranes, promoted the accumulation of osmotica, and inhibited the degradation of or facilitated synthesis of certain proteins. In addition, melatonin improved photosynthesis by inhibiting stomatal closure, enhancing light energy absorption, and promoting electron transport in PSII. Moreover, transcription of 11 genes for enzymes involved in CO2 fixation (Rubisco, PGK, GAPA, FBA, FBP, TIM, TKT, RPK, SEBP, RPI, and RPE) was upregulated in response to melatonin. These results demonstrate that supplemental melatonin could effectively ameliorate the repression of biomass accumulation and photosynthesis caused by drought and thus enhance the seedlings adaptability to drought stress.
Display omitted
•Ozone treatment delayed senescence of fresh‐cut kiwifruit during storage.•Ozone treatment altered phytohormone levels differently.•ABA and SA synergistically delay AsA degradation ...after ozone treatment.•Actinidia03760 is a potential key gene for regulating AsA metabolism.
Ascorbic acid (AsA) is an indicator of the nutritional value of freshly cut kiwifruit during storage at 4℃, and its degradation can be inhibited after ozone treatment (1 mg/L, 10 min). The aim of this study was to elucidate the regulatory mechanism affecting AsA metabolism in fresh-cut kiwifruit after ozone treatment. In this study, ozone treatment not only prevented the decrease in AsA/dehydroascorbic acid and delayed the accumulation of total soluble solids/titratable acidity, but also altered phytohormone levels differently. Transcriptomic profiling combined with cis-acting element and correlation analysis were performed to reveal that abscisic acid and salicylic acid synergistically delay AsA degradation under ozone-treatment conditions. Actinidia03760, encoding ascorbate peroxidase, could be specifically recognized by the bZIP transcription factor and is considered a key candidate gene for further research. Collectively, ozone treatment is a promising method for preserving AsA content and improving the nutrition of fresh-cut kiwifruit.
Starch degradation is considered as an early step in the initiation of kiwifruit postharvest ripening and softening after ethylene treatment, which is driven by various transcription factors (TFs) ...and genes in the carbohydrate pathway. Studies regarding starch degradation have been conducted after ethylene treatment then removal, but early ethylene responsive genes and their function in triggering starch degradation remains unclear. In this study, a continuous sampling approach was conducted with 2 h intervals throughout 24 h treatment. As a result, starch degradation and accumulation of total soluble solid were accelerated after 10 h ethylene treatment. Based on RNA-seq and Real-time quantitative PCR (RT-qPCR) data, three β-Amylase genes, AdBAM3, AdBAM3.1 and AdBAM3L, were significantly up-regulated in ethylene treated samples. Weighted Gene Co-expression Network Analysis (WGCNA) identified TFs that are highly correlated with these three BAM genes, based on gene expression patterns. AdVAL2 (a B3 domain-containing transcription factor) and AdKAN2 (a MYB-like domain-containing transcription factor) were found to transcriptionally repress the promoter activity of AdBAM3 and AdBAM3L, respectively. Additionally, the expression of both AdVAL2 and AdKAN2 was observed to be repressed by ethylene treatment. Transient overexpression analysis confirmed the inhibitory effect of AdVAL2 and AdKAN2 on the expression of BAM genes, resulting in starch accumulation in kiwifruit. Altogether, continuous sampling during ethylene exposure has revealed that these early ethylene responsive TFs could be the potential triggers for starch degradation.
•Conduct continuous dense sampling during the ethylene treatment in kiwifruit.•Starch degradation is an early step in initiation of kiwifruit postharvest ripening.•AdBAM3/3 L could be crucial initiating enzymes for starch degradation.•Ethylene initiates starch degradation via inhibition of BAM expression by AdKAN2/VAL2.
PDF
