1. Plastoquinone In and Beyond Photosynthesis.
- Author
-
Havaux, Michel
- Subjects
- *
REACTIVE oxygen species , *PHOTOSYNTHESIS , *ELECTRON transport , *CHLOROPLAST membranes , *PHOTOSYSTEMS , *COFACTORS (Biochemistry) , *CAROTENES , *GENE expression - Abstract
Plastoquinone-9 (PQ-9) is an essential component of photosynthesis that carries electrons in the linear and alternative electron transport chains, and is also a redox sensor that regulates state transitions and gene expression. However, a large fraction of the PQ pool is located outside the thylakoid membranes, in the plastoglobules and the chloroplast envelopes, reflecting a wider range of functions beyond electron transport. This review describes new functions of PQ in photoprotection, as a potent antioxidant, and in chloroplast metabolism as a cofactor in the biosynthesis of chloroplast metabolites. It also focuses on the essential need for tight environmental control of PQ biosynthesis and for active exchange of this compound between the thylakoid membranes and the plastoglobules. Through its multiple functions, PQ connects photosynthesis with metabolism, light acclimation, and stress tolerance. Plastoquinone (PQ)-9 is an electron carrier that plays an essential role in photosynthesis where it is involved in linear and alternative electron flows. However, the functions of PQ go far beyond photosynthesis. PQ-9 is a multilocation compound that is partitioned in the chloroplast between thylakoids, plastoglobules, and envelopes. Its distribution is modulated dynamically by various regulatory enzymes as a function of the environmental conditions. The redox state of the PQ pool plays a crucial role in various functional and metabolic processes, such as light acclimation, biosynthesis of metabolites, and gene expression. PQ is a potent antioxidant that scavenges reactive oxygen species and mitigates lipid peroxidation in planta , supplementing the photoprotection provided by β-carotene in photosystem II and tocopherols in the thylakoid lipid phase. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF