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.
Highlights
Reactive oxygen species (ROS) comprise both radical and nonradical forms
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Expression of genes involved in ethylene biosynthesis, perception and signaling in Arabidopsis exposed to salt or water stress strongly varied between the wild type and vte4 mutants, but not as much as between vte1 and control [138]
Summary
Reactive oxygen species (ROS) comprise both radical and nonradical forms. The radical ROS include superoxide (O2−), hydroperoxide (HO2), hydroxyl radical (OH) and organic radicals, such as alkoxy and peroxy radicals (RO and ROO, respectively). Chloroplasts are the main site of ROS generation in plant cells under light Stress conditions, such as excessive light exposure, cause enhanced ROS formation. The important role in protection of plastids against ROS is played by prenyllipid antioxidants belonging to isoprenoid chromanols and quinols, which are able to scavenge oxygen and organic radicals, as well as quench and scavenge 1O2 These compounds are crucial for protection of membrane lipids from lipid peroxidation. It is worth mentioning here that thylakoid-membrane fluidity is increased with the presence of lipids with polyunsaturated fatty-acid residues, which are much more prone to oxidation than saturated lipids Apart from their antioxidant function, prenyllipids are known to play a role in cellular signaling [8,9]
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