Abstract
Formylated phloroglucinol compounds (FPCs) are a class of plant specialized metabolite present in the Myrtaceae family, especially in the genus Eucalyptus. FPCs are widely investigated due to their herbivore deterrence properties and various bioactivities of pharmaceutical relevance. Despite the increasing number of studies elucidating new FPCs structures and bioactivity, little is known about the role of those compounds in planta, and the effects of environmental stresses on FPC concentration. Ozone (O3) and wounding are key stress factors regularly confronted by plants. In this study, we investigated how O3, wounding, and their combination affected individual and total FPC foliar concentration of the economically important species Eucalyptus globulus. Six individual FPCs, including five macrocarpals and one sideroxylonal, showed different response patterns to the single and combined stresses. Total macrocarpals only increased under single O3 treatment, whereas total sideroxylonals only increased in response to wounding treatment, suggesting different physiological roles played by the two groups of FPCs predominantly existing in E. globulus foliage. Total FPCs increased significantly under individual wounding and O3 treatments but not under the combined treatment. A principal component analysis indicated that all different treatments had unique FPC fingerprints. Total phenolic contents increased in all O3 and wounding treatments, and a marginally positive correlation was found between total FPCs and total phenolic contents. We suggest that, depending on the concentration and composition, FPCs play multiple physiological roles in planta, including serving as antioxidants to scavenge the reactive oxygen species brought about by O3 and wounding stresses.
Highlights
Ozone (O3 ) is considered as a key air pollutant formed in the troposphere by photochemical reactions between nitrogen oxides (NOx ), and volatile organic compounds (VOCs) such as hydrocarbons in the presence of the sunlight [1,2]
The detected Formylated phloroglucinol compounds (FPCs) were classified into two main groups of FPCs—macrocarpals and sideroxylonals—and analyzed by the UHPLC-DAD-ESI-Q-TOF-MS/MS, combining parental ion accurate mass and diagnostic
Considering that there are very few studies focusing on FPCs response to environmental stresses, the results presented here will improve our understandings of the possible role of individual FPCs in plant defense mechanisms
Summary
Ozone (O3 ) is considered as a key air pollutant formed in the troposphere by photochemical reactions between nitrogen oxides (NOx ), and volatile organic compounds (VOCs) such as hydrocarbons in the presence of the sunlight [1,2]. Elevated O3 can cause acute morphological, physiological, and biochemical changes in plants. It can severely curb photosynthesis and other primary metabolic reactions and has an especially large effect on specialized plant metabolism, which plays an important role in directly and indirectly alleviating the damages caused by O3 [7,8,9,10,11,12,13,14]. In addition to changes in terpenoid metabolism, accumulation of phenolics including phenylpropanoids, flavonoids, tannins, and anthocyanins have been shown to be strongly enhanced by O3 , and possibly involved in scavenging O3 -induced ROS [11,15,16]
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