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The plastoquinone pool outside the thylakoid membrane serves in plant photoprotection as a reservoir of singlet oxygen scavengers.

Autor: Ksas B., Legeret B., Ferretti U., Chevalier A., Pospíšil P., Alric J., Havaux M.Published: Plant, Cell & Environment 41(10), 2277-2287Year: 2018

The Arabidopsis vte1 mutant is devoid of tocopherol and plastochromanol (PC-8). When exposed to excess light energy, vte1 produced more singlet oxygen (1O2) and suffered from extensive oxidative damage compared to the wild type. Here we show that overexpressing the SOLANESYL DIPHOSPHATE SYNTHASE 1 (SPS1) gene in vte1 induced a marked accumulation of total plastoquinone (PQ-9) and rendered the vte1 SPS1oex plants tolerant to photooxidative stress, indicating that PQ-9 can replace tocopherol and PC-8 in photoprotection. High total PQ-9 levels were associated with a noticeable decrease in 1O2 production and higher levels of PQ-C, a 1O2-specific PQ-9 oxidation product. The extra PQ-9 molecules in the vte1 SPS1oex plants were stored in the plastoglobules and the chloroplast envelopes, rather than in the thylakoid membranes, whereas PQ-C was found almost exclusively in the thylakoid membranes. Upon exposure of wild-type plants to high light, the thylakoid PQ-9 pool decreased, while the extra-thylakoid pool remained unchanged. In vte1 and vte1 SPS1oex plants, the PQ-9 losses in high light were strongly amplified, affecting also the extra-thylakoid pool, and PQ-C was found in high amounts in the thylakoids. We conclude that the thylakoid PQ-9 pool acts as a 1O2 scavenger and is replenished from the extra-thylakoid stock.

Department of Biophysics

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Palacký University in Olomouc, Czech Republic

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