Postharvest fungal decay remains one of the major constraints limiting citrus storage and commercialization. Although plant-derived extracts have emerged as promising alternatives to synthetic fungicides, their biological mechanisms underlying postharvest protection remain poorly understood. Here, we investigated the postharvest preservation efficacy and underlying biological basis of Camellia oleifera Defatted-Seed Extract (CDSE) in citrus fruit through integrated physiological, microbiological, transcriptomic, and metabolomic analyses. CDSE treatment markedly reduced postharvest decay and delayed fruit softening without compromising fruit quality. In vitro and in vivo assays demonstrated that CDSE exhibited broad-spectrum antifungal activity against major citrus postharvest pathogens. Mechanistically, CDSE directly disrupted the plasma membrane integrity of Penicillium digitatum, resulting in severe hyphal damage and inhibited fungal growth. Meanwhile, CDSE maintained cell wall homeostasis by preserving lignin, cellulose, and protopectin contents while suppressing the activities and expression of cell wall-degrading enzymes. Transcriptome analysis further revealed that CDSE induced extensive defense-related transcriptional reprogramming, characterized by activation of plant–pathogen interaction pathways, phenylpropanoid biosynthesis, and immune-associated genes, including CERK, NPR, and multiple PR genes. Metabolomic profiling supported these transcriptional changes by demonstrating enhanced accumulation of phenolic acids, flavonoids, biogenic amines, and antioxidant-related metabolites involved in structural reinforcement and defense responses. Collectively, our results demonstrate that CDSE alleviates citrus postharvest decay through a dual mode of action by simultaneously suppressing pathogen growth and reinforcing host defense. This work reveals the biological basis underlying CDSE-mediated postharvest protection and provides a sustainable strategy for developing plant-derived preservatives to improve postharvest disease management and reduce food losses.
Lily (Lilium spp.) is one of the most popular cut flowers in the global flower market. Flower senescence significantly influences the quality and economic value of ornamental plants. However, the mechanisms underlying lily flower senescence remain largely unexplored. This study identifies LoWRKY75 as a key regulator of salicylic acid (SA) and jasmonic acid (JA)-mediated flower senescence in lily. Silencing LoWRKY75 delayed the senescence of lily flowers, whereas its overexpression (OE) accelerated this process. Through transcriptome analysis of LoWRKY75 OE samples and subsequent functional analysis, LoNAC2 was identified as a downstream positive regulator within the LoWRKY75-mediated flower senescence pathway. The concentrations of SA and JA decreased in both LoWRKY75 and LoNAC2-silenced lily tepal samples but increased in the LoWRKY75 and LoNAC2 OE samples. LoWRKY75 directly binds to the promoters of LoNAC2 and SA biosynthesis-related gene PHENYLALANINE AMMONIA-LYASE 2 (LoPAL2), but does not bind to the promoter of LIPOXYGENASE 5 (LoLOX5), a key gene in JA biosynthesis. Conversely, LoNAC2 binds to the promoters of both LoPAL2 and LoLOX5. This study elucidates the regulatory mechanism of the LoWRKY75-LoNAC2 module in flower senescence by activating the SA and JA biosynthesis pathways, thereby offering new insights into hormone-mediated flower senescence in lilies.
Water-in-water (W/W) emulsions have attracted considerable interest in the food field owing to their entirely aqueous nature, oil-free composition and high biocompatibility. However, their application remains constrained by limited storage lifespan (typically several days to one month). In this study, ultra-long-term stable Pickering water-in-water (W/W) emulsions were successfully fabricated using sodium caseinate (SC) as the dispersed phase, pectin as the continuous phase, and chitin nanocrystals (ChNCs) as particle stabilizers. The optimized W/W Pickering emulsion could be stored at room temperature for 6 months without phase separation while largely preserving its original microstructure. First, the phase behaviour of the SC/pectin system was investigated. Subsequently, the influence of ChNCs concentration on the physicochemical properties and stability of the W/W emulsions was systematically investigated through appearance, droplet size distribution, microstructure, rheology, and multiple light scattering analysis. The results suggested that the emulsion stability initially increased and then decreased as the ChNCs content increased from 0.04% to 0.3% (w/v). Optimal stability was achieved at a ChNCs concentration of 0.2% (w/v), at which the emulsion could be stored at room temperature for up to 180 days. In addition, the emulsion demonstrated good resistance to thermal treatment, freeze-thaw cycling, and ions strength. Finally, the potential of the W/W emulsion as a delivery system was evaluated using catechin as a model bioactive compound. The results demonstrated that encapsulation within W/W Pickering emulsions significantly enhanced the ultraviolet stability of catechin and improved its bioaccessibility during in vitro digestion.
Scoparone is a stress-induced phytoalexin that accumulates in citrus fruit; however, the mechanism underlying its biosynthesis remains unclear. In this study, a coumarin synthase gene, CsCOSY, was identified and investigated for its putative role in scoparone biosynthesis and resistance against P. italicum through expression analysis, molecular docking, and transient expression assays. The results showed that the expression of CsCOSY was markedly induced by wounding or inoculation with the virulence-attenuated ΔPiCreA mutant of P. italicum, and this induction was positively correlated with scoparone accumulation. Furthermore, molecular docking predicted a structurally favorable binding of CsCOSY to both 6-hydroxyferuloyl-CoA and 2,4-dihydroxycinnamoyl-CoA. Moreover, transient overexpression or silencing of CsCOSY altered scoparone accumulation and was associated with corresponding changes in the expression of upstream phenylpropanoid pathway genes in citrus fruit. Accordingly, transient overexpression of CsCOSY significantly reduced lesion diameter caused by blue mold, whereas silencing CsCOSY enhanced lesion development. Together, these findings indicate that CsCOSY contributes to stress-induced scoparone biosynthesis and postharvest resistance against P. italicum in citrus fruit, offering new insights into the metabolic regulation of phytoalexin-mediated defense in citrus.
High-intensity ultrasound (HIU)-assisted preparation of Pickering emulsion gels has been widely applied in the food, cosmetics, and pharmaceutical fields. However, conventional ultrasound treatments are typically employed as a pretreatment or modification step for soy protein isolate (SPI) prior to emulsion gel formation, resulting in lengthy processes, high energy consumption, and complex operations. This study investigated the effects of different SPI concentrations (1%, 4%, 6%, 8%, and 10% w/w) on the functional properties and gel structure of Pickering emulsion gels containing 60% (v/v) oil under short-duration ultrasound treatment. Results showed that intact emulsion gels were formed at SPI concentrations ranging from 4% to 10% (w/w) after 30 s of ultrasound treatment. Among these, the emulsion gel prepared with 8% SPI exhibited the highest gel strength (118.80 ± 1.61 g), the smallest droplet diameter (0.7385 ± 0.0765 μm), and optimal water-holding capacity of 100%. These findings indicate that emulsion viscosity and protein concentration are key factors influencing emulsion gel formation. Furthermore, Fourier transform infrared (FTIR) spectroscopy analysis revealed that no significant changes in protein secondary structure occurred within the SPI concentration range of 4%-10% (w/w). Confocal laser scanning microscopy (CLSM) analysis further demonstrated that the stability of the SPI Pickering emulsion gels was primarily attributed to the close packing of oil droplets, as well as bridging interactions and non-covalent interactions among interfacial proteins. This study provides a novel approach for the direct preparation of SPI Pickering emulsion gels using short-duration, high-intensity ultrasound treatment.
