Department of Biomolecular Sciences, The Weizmann Institute of Science, 76100, Rehovot, Israel.
Microalgal Biotechnology Laboratory, French Associates Institute for Agriculture and Biotechnology of Drylands, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede-Boker Campus, Beer-Sheva, 8499000, Israel.
Planta. 2019 Jan;249(1):31-47. doi: 10.1007/s00425-018-3050-3. Epub 2018 Nov 23.
Hypercarotenogenesis in green algae evolved by mutation of PSY that increased its transcription at high light, disintegration of the eyespot in Dunaliella and acquisition of the capacity to export carotenoids from chloroplasts in Haematococcus. Carotenoids (Car) are lipid-soluble pigments synthesized in plants, algae, bacteria and fungi. Car have strong antioxidative properties and as such are utilized to reduce the danger of different diseases in humans. Two green microalgae are utilized as rich natural sources for Car: Dunaliella salina/bardawil accumulates 10% (w/w) β-carotene (βC), which is also pro-vitamin A, and Haematococcus pluvialis accumulates 4% (w/w) astaxanthin (Ast), the strongest antioxidant among Car. D. bardawil accumulates βC in plastoglobules within the chloroplast, whereas H. pluvialis deposits Ast in cytoplasmic lipid droplets (CLD). In this review we compare the hypercarotenogenic responses (HCR) in Dunaliella and in Haematococcus and try to outline hypothetical evolutionary pathways for its origin. We propose that a mutation in phytoene synthetase that increased its transcription level in response to high light stress had a pivotal role in the evolution of the HCR. Proteomic analyses indicated that in D. bardawil/salina the HCR evolved from dissociation and amplification of eyespot lipid globules. The more robust HCR in algae that accumulate carotenoids in CLD, such as H. pluvialis, required also acquisition of the capacity to export βC out of the chloroplast and its enzymatic conversion into Ast.
藻类的类胡萝卜素过量生成是通过 PSY 突变进化而来的，这种突变增加了 PSY 在高光下的转录，破坏了杜氏盐藻中的眼点，并获得了将类胡萝卜素从叶绿体中输出的能力。类胡萝卜素（Car）是植物、藻类、细菌和真菌合成的脂溶性色素。Car 具有很强的抗氧化特性，因此被用于降低人类罹患各种疾病的风险。两种绿藻被用作 Car 的丰富天然来源：盐生杜氏藻/巴尔达维氏盐藻积累 10%（w/w）β-胡萝卜素（βC），βC 也是维生素 A 的前体，雨生红球藻积累 4%（w/w）虾青素（Ast），Ast 是 Car 中最强的抗氧化剂。D. bardawil 将 βC 积累在叶绿体中的质体小球体中，而 H. pluvialis 将 Ast 沉积在细胞质脂滴（CLD）中。在这篇综述中，我们比较了杜氏盐藻和雨生红球藻的类胡萝卜素过量生成反应（HCR），并试图概述其起源的假设进化途径。我们提出，在植物烯醇合成酶中发生的突变，增加了其在高光胁迫下的转录水平，在 HCR 的进化中起了关键作用。蛋白质组学分析表明，在 D. bardawil/salina 中，HCR 是从眼点脂质小球体的解离和扩增进化而来的。在积累 CLD 类胡萝卜素的藻类中，如 H. pluvialis，更强大的 HCR 还需要获得将 βC 从叶绿体中输出并将其酶转化为 Ast 的能力。
