UV-B Pre-treatment Alters Phenolics Response to Monilinia fructicola Infection in a Structure-Dependent Way in Peach Skin

Abstract

Phenolic compounds represent a large class of secondary metabolites, involved in multiple functions not only in plant life cycle, but also in fruit during post-harvest. phenolics play a key role in the response to biotic and abiotic stresses, thus their accumulation is regulated by the presence of environmental stimuli. The present work aimed to investigate how different pre-UV-B-exposures can modulate the phenolic response of peach fruit infected with Monilinia fructicola. Through HPLC-DAD-MSn, several procyanidins, phenolic acids, flavonols, and anthocyanins were detected. Both UV-B radiation and fungal infection were able to stimulate the accumulation of phenolics, dependent on the chemical structure. Regarding UV-B exposure, inoculated with sterile water, 3 h of UV-B radiation highest concentration of phenolics was found, especially flavonols and cyanidin-3-glucoside far from the wound. However, wounding decreased the phenolics in the region nearby. When peaches were pre-treated with 1 h of UV-B radiation, the fungus had an additive effect in phenolic accumulation far from the infection, while it had a subtractive effect with 3 h of UV-B radiation, especially for flavonols. Canonical discriminant analysis and Pearson correlation revealed that all phenolic compounds, except procyanidin dimer, were highly regulated by UV-B radiation, with particularly strong correlation for quercetin and kaempferol glycosides, while phenolics correlated with the fungus infection were quercetin-3-galactoside, quercetin-3-glucoside, kaempferol-3-galactoside and isorhamnetin-3-glucoside. Modulation of pathogen-induced phenolics also far from inoculation site might suggest a migration of signaling molecules from the infected area to healthy tissues.

Beyond the Visible and Below the Peel: How UV-B Radiation Influences the Phenolic Profile in the Pulp of Peach Fruit. A Biochemical and Molecular Study

“…These results were in contrast to what was observed in the peel of UV-B-treated peach fruit. Santin et al (2018a) found a consistent accumulation of anthocyanins 36 h after both the 10and the 60-min UV-B exposure (1.92-and 2.53-fold increase, respectively), and also Santin et al (2018b) displayed a higher cyanidin-3-glucoside concentration following a 3-and 12-h UV-B-treatment. Anthocyanins play a key role in photoprotection against high-energy radiations, such as UV (Solovchenko and Schmitz-Eiberger, 2003;Guo et al, 2008;Schreiner et al, 2012).…”

“…Similarly, the kaempferol 3-rutinoside was found to be positively influenced by the UV-B radiation also in the present study. Besides, Santin et al (2018b) observed an increase also in isorhamnetin concentration in the 3-h UV-B-treated fruit considering all the individual isorhamnetins detected, which were the 3-rutinoside, the 3-galactoside and the 3-glucoside. In the current work, isorhamnetin 3-rutinoside was likewise significantly increased after 24 h from the 60-min UV-B exposure.…”

“…Another study on peeled onion bulbs exposed to a combination of UV-A, -B and -C radiations (18 W m −2 ) showed a 2fold increase in flavonol concentration (Rodov et al, 2010). Also in the peel of peach fruit, 3-and 6-h UV-B treatments (1.36 W m −2 ) were effective in inducing a significant, strong accumulation of flavonols after 24 h from the exposure by 174 and 76%, respectively (Santin et al, 2018b). Particularly, both the kaempferols detected in that work, the 3-rutinoside and the 3-galactoside, underwent a significant increase in the UV-B-treated samples.…”

Unravelling the consecutive glycosylation and methylation of flavonols in peach in response to UV‐B irradiation

“…Previously, PpMYB15 and PpMYBF1 were identified as functional flavonol‐specific positive regulators in peach fruit (Cao et al, 2019). The main flavonols in peach fruit include I3Rut, Q3Rut, K 3‐ O ‐rutinoside (K3Rut) and I3Glc (Santin et al, 2018; Scattino et al, 2014). Therefore, peach is a good material for unravelling the mechanism and sequence of consecutive glycosylation and methylation reactions.…”

Zn(II) Complex of Plant Phenolic Chlorogenic Acid: Antioxidant, Antimicrobial and Structural Studies

“…5-CQA plays an important role in defense against biotic and abiotic stress in plants, and is considered to be an intermediate molecule in lignin biosynthesis pathway [14]. Many studies reported accumulation of chlorogenic acid in tissue exposed to different stress factors, e.g., an increase in salinity [15], bacterial infection [16], ultraviolet (UV-B) radiation [17], toxic metals [18,19] and other related with an increase in production of reactive oxygen species (ROS) which damage cellular membrane and react with plant cell components causing disruption of metabolic pathways.…”