Increased photosystem II translation efficiency as an important photoprotective mechanism in an Arabidopsis thaliana ecotype (Tibet-0) adapted to high light environments

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The Qinghai-Tibet Plateau (QTP) is the highest and largest young plateau in the world, with a wide variety of extreme environments. Due to the low density of air and high transparency of the atmosphere, QTP has abundant sunshine and high light intensity. It is important for plants in QTP to evolve mechanism of photoprotection to adapt the high-light conditions. Arabidopsis thaliana is an important model organism in plant science and molecular biology. Tibet-0 was the first Arabidopsis thaliana ecotype collected in the QTP, at >4000 m above sea level. Here, we systematically analyzed the photosynthetic responses of Tibet-0 to high light. Our results show that Tibet-0 has more efficient PSII photosynthetic activity under continuous high-light conditions (1000 μmol photons m−2 s−1) compared to Columbia (Col-0). Chlorophyll fluorescence analysis showed that Tibet-0 exhibited enhanced PSII quantum yield (ФPSII), photochemical quenching (qP), and electron transport rate (ETR) under high-light conditions. However, anthocyanin accumulation was lower in Tibet-0. Blue Native-PAGE and immunoblot analyses showed that the abundances of PSII complexes and subunits were significantly higher in Tibet-0 vs. Col-0 under standard and high-light conditions. Notably, the associations of PSII core subunit mRNAs psbA, psbB, psbC and psbD with chloroplast ribosomal protein were significantly higher in Tibet-0, based on ribosome-nascent chain complex (RNC)-quantitative PCR. Moreover, the expression of amounts of chloroplast ribosomal protein-related genes was activated in Tibet-0 after high-light treatment. These results suggest that the enhanced photoprotection capability of Tibet-0 arises via constitutively higher translation efficiency for PSII proteins due to activated ribosomal protein expression. This study thus provides insight into the mechanism underlying high-light adaptation in plants at high altitudes.