Deciphering the Metabolic Pathways of Pitaya Peel after Postharvest Red Light Irradiation

Abstract

Red light irradiation can effectively prolong the shelf-life of many fruit. However, little is known about red light-induced metabolite and enzyme activities. In this study, pitaya fruit was treated with 100 Lux red light for 24 h. Red light irradiation significantly attenuated the variation trend of senescence traits, such as the decrease of total soluble solid (TSS) and TSS/acidity (titratable acidity, TA) ratio, the increase of TA, and respiratory rate. In addition, the reactive oxygen species (ROS) related characters, primary metabolites profiling, and volatile compounds profiling were determined. A total of 71 primary metabolites and 67 volatile compounds were detected and successfully identified by using gas chromatography mass spectrometry (GC-MS). Red light irradiation enhanced glycolysis, tricarboxylic acid (TCA) cycle, aldehydes metabolism, and antioxidant enzymes activities at early stage of postharvest storage, leading to the reduction of H2O2, soluble sugars, organic acids, and C-6 and C-7 aldehydes. At a later stage of postharvest storage, a larger number of resistance-related metabolites and enzyme activities were induced in red light-treated pitaya peel, such as superoxide dismutase (SOD), ascorbate peroxidase (APX), 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical-scavenging, reducing power, fatty acids, and volatile aroma.

Supplemental red LED light promotes plant productivity, “photomodulates” fruit quality and increases Botrytis cinerea tolerance in strawberry

“…A similar effect was also observed after G treatment, despite the level of alanine accumulated was lower than in plants under B light. However, the general decrease of primary metabolite contents (soluble sugars, amino acids and organic acids) in fruit exposed to R light observed in the present experiment was confirmed by Wu et al (2020), analyzing the R light effect on postharvested pitaya fruit. Indeed, despite the different periods of exposure to light treatment, R light irradiation might accelerate the glycolysis and tricarboxylic acid (TCA) cycle at the enhanced resistance stage, leading to the decrease of soluble sugars and organic acids and slowing the TCA cycle at the senescence stage (Wu et al, 2020).…”

Single-cell and spatial RNA sequencing reveal the spatiotemporal trajectories of fruit senescence

“…Furthermore, some compounds with excellent antioxidant and other biological activities, not previously identified in H. undatus , were detected (Supplementary Data 8 ). Examples include flavonol compound Herbacetin, a natural flavonoid from flaxseed known for its antioxidant, anti-inflammatory, and anticancer activities 51 , 52 . Additionally, Esculin, a coumarin glucoside found in various plants, exhibited anti-inflammatory effects 53 , 54 .…”

“…This study proposed that flavonoids may serve as potential indicators of the senescence process. Flavonoids exhibit excellent ROS scavenging activity, and ROS is closely associated with senescence 52 , 58 . The anti-senescence effects of flavonoids in animals have been confirmed 59 , and the correlation between changes in flavonoid levels and plant senescence processes has been suggested 60 .…”

Light‐emitting diodes (below 700 nm): Improving the preservation of fresh foods during postharvest handling, storage, and transportation

“…Red light (100 Lux) has been shown to reduce the respiration rate of pitaya, as evidenced by a 43.68% reduction in fruit decay rate. It is noteworthy that six kinds of cell wall degradation products decreased significantly on the seventh day of storage, which corresponds to the low decay rate and high hardness of the fruit (Wu et al., 2020). The authors attributed this phenomenon to early red LED irradiation promoting glycolysis and TCA cycling, resulting in a reduction in soluble sugars and organic acids.…”

“…The contents of β‐linalool, 1‐hexanol, palmitoleic acid, and other volatile compounds in pitaya fruit increased rapidly after being irradiated with red light during its aging stage (Wu et al., 2020). The application of specific light irradiation in the postharvest storage environment may regulate discrete biochemical nodes to affect substrate flux, and ultimately achieve the regulation of volatile compound production in plants (Colquhoun et al., 2013).…”