Synergy of Nitric Oxide and 1-Methylcyclopropene Treatment in Prolong Ripening and Senescence of Peach Fruit

Transcription factors PuNAC37/PuWRKY74 and E3 ubiquitin ligase PuRDUF2 inhibit volatile ester synthesis in 'Nanguo' pear

As major contributors to flavor in many fruit species, volatile esters are useful for investigating the regulation of the biosynthesis pathways of volatile aroma compounds in plants. Ethylene promotes the biosynthesis of volatile esters during fruit storage while accelerating fruit ripening; thus, the ethylene perception inhibitor 1-methylcyclopropene (1-MCP) is employed to prolong the shelf life of fruits. However, the mechanisms by which 1-MCP regulates volatiles synthesis remain unclear. In this study, we analyzed the pathway of 1-MCP-mediated volatile ester synthesis in 'Nanguo' pear (Pyrus ussuriensis). 1-MCP significantly decreased volatile ester synthesis during storage. Comparative transcriptome analysis showed that the genes encoding two transcription factors (PuNAC37 and PuWRKY74) and a RING-type E3 ubiquitin ligase that have a domain of unknown function (PuRDUF2) were expressed at high levels, whereas ALCOHOL ACYLTRANSFERASE 1 (PuAAT1), encoding an enzyme responsible for volatile ester synthesis, was expressed at low levels in 1-MCP-treated fruit. Moreover, PuNAC37 inhibited the expression of PuWRKY74 via transcriptional regulation, whereas PuNAC37 and PuWRKY74, after directly binding to the promoter of PuAAT1, synergistically inhibited its expression in 1-MCP-treated fruit. In addition, in vitro and in vivo ubiquitination experiments revealed that PuRDUF2 functions as an E3 ubiquitin ligase that ubiquitinates PuAAT1, causing its degradation via the 26S proteasome pathway following 1-MCP treatment. Subsequent PuAAT1 degradation resulted in a reduction of volatile esters during fruit storage. Our findings provide insights into the complex transcriptional regulation of volatile ester formation in 'Nanguo' pears and contribute to future research on AAT protein ubiquitination in other species.

Exogenous nitric oxide extends longevity in cut Lilium tigrinum flowers by orchestrating biochemical and molecular aspects

Senescence represents a developmentally orchestrated and precisely regulated cascade of events, culminating in the abscission of plant organs and ultimately leading to the demise of the plant or its constituent parts. In this study, we observed that senescence in cut Lilium tigrinum flowers is induced by elevated ABA levels and the hyperactivation of lipoxygenase (LOX) activity. This cascade increased ROS concentrations, heightened oxidative damage, and disrupted cellular redox equilibrium. This was evidenced by elevated lipid peroxidation, attenuated antioxidant machinery, and reduced membrane stability index (MSI). Despite its known role in delaying flower senescence, the specific biochemical and molecular mechanisms by which nitric oxide (NO) regulates senescence in cut L. tigrinum flowers are not fully elucidated. Specifically, the interactions between NO signaling and ABA metabolism, the regulation of protease activity, and the influence of NO-mediated ROS scavenging, senescence-associated gene expression requires further exploration. Exogenous application of sodium nitroprusside (SNP), a source of NO, mitigated senescence in L. tigrinum cut flowers by upregulating the activity of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and reducing the LOX activity, an indicator of lipid peroxidation. SNP treatment also downregulated the relative expression of senescence-associated gene (SAG12 ),lipoxygenase 1 (LOX1 ), and abscisic aldehyde oxidase 3 (AAO3 ). NO also upregulated defender against apoptotic death 1 (DAD1 ) expression correlated with minimized protease activity and reduced α-amino acid content in SNP-treated tepals. This regulation was accompanied by increased contents of sugars, proteins and phenols and reduced abscisic acid content, which collectively delayed the senesecence and enhanced the longevity of L. tigrinum cut flowers. This study demonstrates that exogenous SNP application can effectively mitigate senescence in cut L. tigrinum flowers by modulating antioxidant enzyme activities, reducing oxidative stress, and regulating the expression of key senescence-associated genes. This study unravels the complex molecular networks involved in NO-mediated senescence delay, which may lead to the development of innovative approaches for improving flower longevity.

Salicylic Acid Spray Delays Sand Pear Fruit Senescence during Room Temperature Shelf Life by Regulating Antioxidant Capacity and Senescence-Related Genes

'Whangkeumbae' (Pyrus pyrifolia) is a variety of sand pear fruit well-known for its smooth surface and good taste. However, the fruit quality is adversely affected by postharvest ethylene production. Therefore, improving postharvest shelf life by regulating fruit senescence is critical to promoting the 'Whangkeumbae' fruit industry. Here, we investigated the effect of salicylic acid (SA) spray on fruit senescence in sand pears during room temperature shelf life. Exogenous SA reduced polyphenol oxidase (PPO) activity and malondialdehyde (MDA) content during room temperature shelf life. Additionally, SA effectively maintained the fruit skin coloration and increased the activity of antioxidant enzymes, such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX). SA treatment inhibited PpPPO1 expression and upregulated PpSOD1, PpAPX6, and PpGST2 expression. Furthermore, SA application downregulated the expression of PpACO2, PpEIN3a, PpNCED1, and PpAOC2, while upregulating PpNPR-1, PpTAR2, and PpCOMT1 during room temperature shelf life. SA treatment also influenced cell wall metabolism and modification genes by inhibiting PpPG1, PpPME2, and PpCEL3 and inducing PpPGIP1 expression. Additionally, SA treatment affected sugar and acid metabolism genes and increased the expression of PpSPS1, PpSUS1, PpSOT1, PpTMT4, PpSWEET15, and PpcyNAD-MDH, but suppressed the expression of PpcyNADP-ME. The Pearson correlation analysis indicated that PPO activity and MDA content were positively correlated with the expression of PpPPO1, PpACO2, PpEIN3a, PpNCED1, PpAOC2, PpPG1, PpPME2, PpCEL3, and PpcyNDA-MDH. Conversely, these factors were negatively associated with the activities of SOD, POD, CAT, and APX, as well as the expression levels of PpSOD1, PpPOD1, PpCAT1, PpAPX6, PpGST2, PpNPR-1, PpTAR2, PpCOMT1, PpPGIP1, PpSPS1, PpSUS1, PpSOT1, PpTMT4, PpSWEET15, and PpcyNAD-MDH. Our results reveal that exogenous SA could delay fruit senescence in sand pear fruit by regulating various biochemical and molecular mechanisms and can be used to effectively extend fruit shelf life during room temperature storage. However, further research is necessary to determine whether the fruits sprayed with SA are suitable for direct human consumption.

Class III Peroxidases (POD) in Pepper (Capsicum annuum L.): Genome-Wide Identification and Regulation during Nitric Oxide (NO)-Influenced Fruit Ripening

The class III peroxidases (PODs) catalyze the oxidation of several substrates coupled to the reduction of H₂O₂ to water, and play important roles in diverse plant processes. The POD family members have been well-studied in several plant species, but little information is available on sweet pepper fruit physiology. Based on the existing pepper genome, a total of 75 CaPOD genes have been identified, but only 10 genes were found in the fruit transcriptome (RNA-Seq). The time-course expression analysis of these genes showed that two were upregulated during fruit ripening, seven were downregulated, and one gene was unaffected. Furthermore, nitric oxide (NO) treatment triggered the upregulation of two CaPOD genes whereas the others were unaffected. Non-denaturing PAGE and in-gel activity staining allowed identifying four CaPOD isozymes (CaPOD I-CaPOD IV) which were differentially modulated during ripening and by NO. In vitro analyses of green fruit samples with peroxynitrite, NO donors, and reducing agents triggered about 100% inhibition of CaPOD IV. These data support the modulation of POD at gene and activity levels, which is in agreement with the nitro-oxidative metabolism of pepper fruit during ripening, and suggest that POD IV is a target for nitration and reducing events that lead to its inhibition.

Advances Postharvest Preservation Technology

Fruits and vegetables are important sources of nutrients such as vitamins, minerals, and bioactive compounds, which provide many health benefits [...].

Nitric Oxide Acts as an Inhibitor of Postharvest Senescence in Horticultural Products

Horticultural products display fast senescence after harvest at ambient temperatures, resulting in decreased quality and shorter shelf life. As a gaseous signal molecule, nitric oxide (NO) has an important physiological effect on plants. Specifically, in the area of NO and its regulation of postharvest senescence, tremendous progress has been made. This review summarizes NO synthesis; the effect of NO in alleviating postharvest senescence; the mechanism of NO-alleviated senescence; and its interactions with other signaling molecules, such as ethylene (ETH), abscisic acid (ABA), melatonin (MT), hydrogen sulfide (H2S), hydrogen gas (H2), hydrogen peroxide (H2O2), and calcium ions (Ca2+). The aim of this review is to provide theoretical references for the application of NO in postharvest senescence in horticultural products.

Effects of Harvest Maturity on the Fruit Quality of Different Flesh-Type Peach Stored at Near-Freezing Point Temperature

To investigate the peach fruit flesh types (soft-melting, hard-melting, stonyhard and non-melting) and harvest maturity level suitable for near-freezing temperature storage (NFTS), eight peach cultivars that had four flesh types were used as test materials. Changes in fruit respiration intensity and ethylene release rates, as well as the differences in quality indexes, such as soluble solids content (SSC), firmness, color difference, pigment content, soluble sugar and organic acid component content, of three fruit maturity levels (70%, 80% and 90% maturity) under NFTS conditions were analyzed and compared. The fruit quality indexes of peach having different maturity levels and flesh types changed little during NFTS. The SSC and total sugar content of hard-melting and stonyhard peach fruit were higher than those of other flesh types during NFTS. Those fruit maintained greater firmness at the end of the storage period. The differences in respiration intensity and ethylene release rate were small, but for fruit coloring, hard-melting fruit performed better than stonyhard fruit. The 80%, compared with the 90%, maturity stage maintained more fruit moisture, had less fruit mass loss and maintained a greater edible firmness. It effectively impeded the fruit senescence process and was the most suitable maturity for NFTS. Thus, the hard-melting peach maintained the highest commercial value and desirable storage characteristics under NFTS conditions, and its 80% maturity level was the most suitable for NFTS.