Ultrasonic treatment suppresses ethylene signaling and prolongs the freshness of spinach

Proposing Signaling Molecules as Key Optimization Targets for Intensifying the Phytochemical Biosynthesis Induced by Emerging Nonthermal Stress Pretreatments of Plant-Based Foods: A Focus on γ-Aminobutyric Acid

Emerging evidence has confirmed the role of emerging nonthermal stressors (e.g., electromagnetic fields, ultrasonication, plasma) in accumulating bioactive metabolites in plant-based food. However, the signal decoding mechanisms behind NonTt-driven phytochemical production remain unclear, hindering postharvest bioactive component intensification. This study aims to summarize the association between signaling molecules and bioactive secondary metabolite production under nonthermal conditions, demonstrating the feasibility of enhancing phytochemical accumulation through signaling molecule crosstalk manipulation. Nonthermal elicitors were found to be capable of inducing stress metabolisms and activating various signaling molecules, similar to conventional abiotic stress. A simplified pathway model for nonthermally induced γ-aminobutyric acid accumulation was proposed with reactive oxygen species and calcium signaling being versatile pathways responsive to nonthermal elicitors. Manipulating signal molecules/pathways under nonthermal conditions can intensify phytochemical biosynthesis. Further research is needed to integrate signaling molecule responses and metabolic network shifts in nonthermally stressed plant-based matrices, balancing quality modifications and intensification of food functionality potential.

Transcriptomic and physiological analysis reveals the possible mechanism of ultrasound inhibiting strawberry (Fragaria × ananassa Duch.) postharvest softening

Ultrasound effectively inhibited strawberry softening but the mechanism was not clear. In this study, physical data including firmness, soluble pectin (SP) contents, pectin esterase (PE), polygalacturonase (PG) activity and transcriptome sequencing data were analyzed to explore the mechanism of strawberry response to ultrasonic treatment. After 24 days storage, the firmness reduction rate and soluble contents (SP) increased rate of the strawberry treated with ultrasound (25 kHz, 0.15 W/cm2) for 3 min decreased 41.70 and 63.12% compared with the control, respectively. While the PG and PE enzyme activities of ultrasound-treated strawberries were significantly lower than control after storage for 18 days. A total of 1,905 diferentially expressed genes (DEGs) were identified between ultrasound-treated and control, with 714 genes upregulated and 1,254 genes downregulated, including 56 genes in reactive oxygen species (ROS), auxin (AUX), ethylene (ETH) and jasmonic acid (JA) signaling pathways. At 0 h, 15 genes including LOX, JMT, ARP, SKP, SAUR, IAA, ARF, and LAX were significantly upregulated compared with the control group, which means reactive oxygen specie, auxin, ethylene and jasmonic acid-mediated signaling pathway respond to ultrasound immediately. ERF109, ERF110, and ACS1_2_6 downregulated before 2 days storage indicated ethylene signaling pathway was inhibited, while after 2 days, 9 genes including ERF027, ERF109, and ERF110 were significantly upregulated indicating that the response of the ethylene signaling pathway was lagging. Therefore, in strawberry ultrasound enhanced ROS scavenging and activated JA biosynthesis, which acts as a signal for delaying the activation of ET signaling pathway, thus suppressing the activity of pectin-degrading enzymes PE and PG, and ultimately inhibiting postharvest softening.

Ultrasound, as a hypomethylating agent, remodels DNA methylation and alters mRNA transcription in winter wheat (Triticum aestivum L.) seedlings

Any treatment that affects seed germination and seedling development is of paramount importance from an agricultural point of view since they are critical prerequisites for successful crop production. In present study, we have examined the after-effect of ultrasonication (at 30 kHz, 70 W for 5 min) of winter wheat (Triticum aestivum L. cv. SE15) seeds on the early seedling growth and development, and accompanying changes in the DNA methylation and transcriptomic pattern in 7-day-old seedlings. We used mRNA-sequencing and whole genome bisulfite sequencing (WGBS) to identify significantly differentially expressed genes (DEGs), significantly differently methylated regions (DMRs) and genes (DMGs). Ultrasonication of seeds did not alter the germination rate but increased both the length and weight of roots and shoots of 7-day-old seedlings significantly by 23%-68% and 16%-28%, respectively. Analyzing the expression intensity of 107,891 genes, significantly differentially expressed sequences related mainly to starch biosynthesis, IAA biosynthesis, photosynthesis and TCA cycle pathways. The same pathways were also affected by DNA-methylation changes. DNA hypomethylation occurred in the global methylation profile after ultrasound treatment altering the accessibility of some genes for transcription. Transcriptomic changes suggested alterations in the crosstalk between IAA and sucrose signaling, enhancement of growth processes, and increased activity of nuclear transcription factor stimulating the transcription of genes having CCAAT motif in the promoter. In the present first whole genome level study, we have identified seed ultrasonication as a priming technique that can act as a hypomethylating agent and thereby is able to modify the mRNA transcription allowing enhanced seedling growth.