低温胁迫会改变小球藻的八氢番茄红素脱氢酶基因（crtP1 和 crtP2）和 ζ-胡萝卜素脱氢酶基因（crtQ）的表达以及细胞类胡萝卜素含量。

Low Temperature Stress Alters the Expression of Phytoene Desaturase Genes (crtP1 and crtP2) and the ζ-Carotene Desaturase Gene (crtQ) Together with the Cellular Carotenoid Content of Euglena gracilis.

机构信息

Plant Molecular and Cellular Biology Laboratory, Department of Biosciences, School of Science and Engineering, Teikyo University, 1-1 Toyosatodai, Utsunomiya, Tochigi, Japan.

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, Japan.

出版信息

Plant Cell Physiol. 2019 Feb 1;60(2):274-284. doi: 10.1093/pcp/pcy208.

DOI:10.1093/pcp/pcy208

PMID:30346581

Abstract

Carotenoids participate in photosynthesis and photoprotection in oxygenic phototrophs. Euglena gracilis, a eukaryotic phytoflagellate, synthesizes several carotenoids: β-carotene, neoxanthin, diadinoxanthin and diatoxanthin. Temperature is one of the most striking external stimuli altering carotenoid production. In the present study, to elucidate the regulation of carotenoid synthesis of E. gracilis in response to environmental stimuli, we functionally identified phytoene desaturase genes (crtP1 and crtP2) and the ζ-carotene desaturase gene (crtQ) of this alga and analyzed expression of those genes and the composition of major carotenoids in cells grown under cold (20ï¿½C) and high-intensity light (HL; 240 ï¿½mol photon m-2 s-1) conditions. 20ï¿½C-HL treatment increased the transcriptional level of the phytoene synthase gene (crtB), and crtP1 and crtP2, whose products catalyze the early steps of carotenoid biosynthesis in this alga. Cultivation at 20ï¿½C under illumination at 55 ï¿½mol photon m-2 s-1 (low-intensity light; LL) decreased the cell concentration, Chl and total major carotenoid content by 61, 75 and 50%, respectively, relative to control (25ï¿½C-LL) cells. When grown at 20ï¿½C-HL, the cells showed a greater decrease in cell concentration and photosynthetic pigment contents than those in 20ï¿½C-LL. β-Carotene, neoxanthin and diadinoxanthin contents were decreased by more than half in 20ï¿½C-LL and 20ï¿½C-HL treatments. On the other hand, when subjected to 20ï¿½C-LL and 20ï¿½C-HL, the cells retained a diatoxanthin content comparable with control cells. Our findings suggested that diatoxanthin plays crucial roles in the acclimation to cold and intense light condition. To the best of our knowledge, this is the first report on a photosynthetic organism possessing dual crtP genes.

摘要

类胡萝卜素参与含氧光合作用生物的光合作用和光保护。绿眼虫，一种真核植物鞭毛藻，合成几种类胡萝卜素：β-胡萝卜素、新黄质、玉米黄质和硅藻黄质。温度是改变类胡萝卜素产生的最显著的外部刺激之一。在本研究中，为了阐明绿眼虫对环境刺激的类胡萝卜素合成的调节，我们功能鉴定了该藻类的八氢番茄红素脱氢酶基因（crtP1 和 crtP2）和 ζ-胡萝卜素脱氢酶基因（crtQ），并分析了这些基因的表达和在低温（20°C）和高光强（HL；240 µmol 光子 m-2 s-1）条件下生长的细胞中主要类胡萝卜素的组成。20°C-HL 处理增加了类胡萝卜素生物合成早期步骤的八氢番茄红素合酶基因（crtB），以及 crtP1 和 crtP2 的转录水平，它们的产物在该藻类中催化类胡萝卜素生物合成的早期步骤。在 55 µmol 光子 m-2 s-1（低光照强度；LL）光照下于 20°C 培养会使细胞浓度、叶绿素和总主要类胡萝卜素含量分别比对照（25°C-LL）细胞降低 61%、75%和 50%。当在 20°C-HL 下生长时，细胞的细胞浓度和光合色素含量的下降比在 20°C-LL 下更大。β-胡萝卜素、新黄质和玉米黄质的含量在 20°C-LL 和 20°C-HL 处理中降低了一半以上。另一方面，当受到 20°C-LL 和 20°C-HL 的处理时，细胞保留了与对照细胞相当的硅藻黄质含量。我们的发现表明硅藻黄质在适应低温和强光条件中起着关键作用。据我们所知，这是第一个报道具有双 crtP 基因的光合生物的报告。