Plant Molecular and Cellular Biology Laboratory, Division of Integrated Science and Engineering, Graduate School of Science and Engineering, Teikyo University Graduate Schools, 1-1 Toyosatodai, Utsunomiya, Tochigi 320-8551, Japan.
Plant Molecular and Cellular Biology Laboratory, Department of Biosciences, School of Science and Engineering, Teikyo University, 1-1 Toyosatodai, Utsunomiya, Tochigi 320-8551, Japan; Laboratory of Complex Biology, Center for Plant Aging Research, Institute for Basic Science, DGIST, Daegu 42988, Republic of Korea; Center for Bioscience Research and Education, Utsunomiya University, 350 mine-machi, Utsunomiya, Tochigi 321-8505, Japan.
J Photochem Photobiol B. 2020 Aug;209:111950. doi: 10.1016/j.jphotobiol.2020.111950. Epub 2020 Jul 4.
Carotenoids are essential components of photosynthetic organisms including land plants, algae, cyanobacteria, and photosynthetic bacteria. Although the light-mediated regulation of carotenoid biosynthesis, including the light/dark cycle as well as the dependence of carotenoid biosynthesis-related gene translation on light wavelength, has been investigated in land plants, these aspects have not been studied in microalgae. Here, we investigated carotenoid biosynthesis in Euglena gracilis and found that zeaxanthin accumulates in the dark. The major carotenoid species in E. gracilis, namely β-carotene, neoxanthin, diadinoxanthin and diatoxanthin, accumulated corresponding to the duration of light irradiation under the light/dark cycle, although the translation of carotenoid biosynthesis genes hardly changed. Irradiation with either blue or red-light (3 μmol photons m s) caused a 1.3-fold increase in β-carotene content compared with the dark control. Blue-light irradiation (300 μmol photons m s) caused an increase in the cellular content of both zeaxanthin and all trans-diatoxanthin, and this increase was proportional to blue-light intensity. In addition, pre-irradiation with blue-light of 3 or 30 μmol photons m s enhanced the photosynthetic activity and tolerance to high-light stress. These findings suggest that the accumulation of β-carotene is regulated by the intensity of light, which may contribute to the acclimation of E. gracilis to the light environment in day night conditions.
类胡萝卜素是包括陆地植物、藻类、蓝细菌和光合细菌在内的光合生物的重要组成部分。尽管陆地植物中已经研究了光介导的类胡萝卜素生物合成的调控，包括光/暗周期以及类胡萝卜素生物合成相关基因翻译对光波长的依赖性，但在微藻中尚未研究这些方面。在这里，我们研究了眼虫(Euglena gracilis)中的类胡萝卜素生物合成，发现叶黄素在黑暗中积累。眼虫中主要的类胡萝卜素种类，即β-胡萝卜素、新黄质、二氢玉米黄质和玉米黄质，在光/暗周期下的光照射持续时间内积累，尽管类胡萝卜素生物合成基因的翻译几乎没有变化。与黑暗对照相比，用蓝或红光（3 μmol 光子 m s）照射会使 β-胡萝卜素含量增加 1.3 倍。蓝光（300 μmol 光子 m s）照射会导致叶黄素和全反式玉米黄质的细胞含量增加，并且这种增加与蓝光强度成正比。此外，用 3 或 30 μmol 光子 m s 的蓝光预先照射增强了光合作用活性和对高光胁迫的耐受性。这些发现表明，β-胡萝卜素的积累受光强度的调节，这可能有助于眼虫适应日夜条件下的光照环境。
