Antioxidant and Signaling Role of Plastid-Derived Isoprenoid Quinones and Chromanols

Abstract

Plant prenyllipids, especially isoprenoid chromanols and quinols, are very efficient low-molecular-weight lipophilic antioxidants, protecting membranes and storage lipids from reactive oxygen species (ROS). ROS are byproducts of aerobic metabolism that can damage cell components, they are also known to play a role in signaling. Plants are particularly prone to oxidative damage because oxygenic photosynthesis results in O2 formation in their green tissues. In addition, the photosynthetic electron transfer chain is an important source of ROS. Therefore, chloroplasts are the main site of ROS generation in plant cells during the light reactions of photosynthesis, and plastidic antioxidants are crucial to prevent oxidative stress, which occurs when plants are exposed to various types of stress factors, both biotic and abiotic. The increase in antioxidant content during stress acclimation is a common phenomenon. In the present review, we describe the mechanisms of ROS (singlet oxygen, superoxide, hydrogen peroxide and hydroxyl radical) production in chloroplasts in general and during exposure to abiotic stress factors, such as high light, low temperature, drought and salinity. We highlight the dual role of their presence: negative (i.e., lipid peroxidation, pigment and protein oxidation) and positive (i.e., contribution in redox-based physiological processes). Then we provide a summary of current knowledge concerning plastidic prenyllipid antioxidants belonging to isoprenoid chromanols and quinols, as well as their structure, occurrence, biosynthesis and function both in ROS detoxification and signaling.

Light Intensity- and Spectrum-Dependent Redox Regulation of Plant Metabolism

“…Several enzymes of their synthesis are regulated by light conditions, the redox system, and the HY5 transcription factor ( Table A4 ). Among terpenoids, quinones and chromanol have a role in the response to HL stress [ 219 ]. Light control of the biosynthesis of monoterpene precursors was shown in the Moth orchid ( Phalaenopsis bellina ) since the promoter of the gene encoding geranyl diphosphate synthase (GPPS, catalysing the mentioned process) was reported to have a light-responsive element [ 220 ].…”

A unique flavoenzyme operates in ubiquinone biosynthesis in photosynthesis-related eukaryotes

“…In land plants, CoqF is the sole C 6-hydroxylase. Compared to di-iron monooxygenase, flavin-containing proteins might be less vulnerable to damage by reactive oxygen species (ROS) that are often very high in photosynthetic cells ( 40 ). The CoqF distribution pattern reflects that of another flavin-dependent enzyme present in mitochondria, l -galactonolactone dehydrogenase (GLDH), the terminal enzyme of ascorbic acid (vitamin C) biosynthesis, which is present in eukaryotes of photosynthetic lineages that can make ascorbic acid without producing ROS as by-products of synthesis ( 41 ).…”

Shedding a New Light on Skin Aging, Iron- and Redox-Homeostasis and Emerging Natural Antioxidants

“…Photosynthetic organisms are particularly susceptible to oxidative damage because oxygenic photosynthesis causes an increased oxygen concentration in chloroplasts. Chromanols are also important prenyllipid AO constituents which are capable of scavenging oxygen and organic radicals, as well as quenching and scavenging 1 O 2 , and thereby protecting them against ROS and consequent structural damages [262]. In fact, for many years, vit E was recognised solely as an AO due to its 1 O 2 quenching property.…”