Laboratoire de Physiologie Cellulaire et Végétale, Unité Mixte de Recherche 5168, Centre National de la Recherche Scientifique, Commissariat à l'Energie Atomique, Institut National de la Recherche Agronomique, Université Grenoble Alpes, Institut de Biosciences Biotechnologies de Grenoble, Commissariat à l'Energie Atomique Grenoble, 38000 Grenoble, France.
Institut des Biomolécules Max Mousseron, Unité Mixte de Recherche 5247, Université de Montpellier, Centre National de la Recherche Scientifique, Ecole Nationale Supérieure de Chimie de Montpellier, F-34093 Montpellier cedex 05, France.
Plant Physiol. 2018 Nov;178(3):1344-1357. doi: 10.1104/pp.18.00925. Epub 2018 Sep 20.
The ecological success of diatoms requires a remarkable ability to survive many types of stress, including variations in temperature, light, salinity, and nutrient availability. On exposure to these stresses, diatoms exhibit common responses, including growth arrest, impairment of photosynthesis, production of reactive oxygen species, and accumulation of triacylglycerol (TAG). We studied the production of cyclopentane oxylipins derived from fatty acids in the diatom in response to oxidative stress. lacks the enzymatic pathway for producing cyclopentane-oxylipins, such as jasmonate, prostaglandins, or thromboxanes. In cells subjected to increasing doses of hydrogen peroxide (HO), we detected nonenzymatic production of isoprostanoids, including six phytoprostanes, three F-isoprostanes, two F-isoprostanes, and three F-neuroprostanes, by radical peroxidation of α-linolenic, arachidonic, eicosapentaenoic, and docosahexanoic acids, respectively. HO also triggered photosynthesis impairment and TAG accumulation. F-phytoprostanes constitute the major class detected (300 pmol per 1 million cells; intracellular concentration, ∼4 µm). Only two glycerolipids, phosphatidylcholine and diacylglycerylhydroxymethyl-trimethyl-alanine, could provide all substrates for these isoprostanoids. Treatment of with nine synthetic isoprostanoids produced an effect in the micromolar range, marked by the accumulation of TAG and reduced growth, without affecting photosynthesis. Therefore, the emission of HO and free radicals upon exposure to stresses can lead to glycerolipid peroxidation and nonenzymatic synthesis of isoprostanoids, inhibiting growth and contributing to the induction of TAG accumulation via unknown processes. This characterization of nonenzymatic oxylipins in opens a field of research on the study of processes controlled by isoprostanoid signaling in various physiological and environmental contexts in diatoms.
硅藻的生态成功需要一种非凡的能力，使其能够在许多类型的压力下生存，包括温度、光照、盐度和养分供应的变化。暴露于这些压力时，硅藻表现出共同的反应，包括生长停滞、光合作用受损、活性氧物质的产生和三酰基甘油(TAG)的积累。我们研究了在氧化应激下，从脂肪酸中产生的环戊烷氧脂素在硅藻 中的产生情况。 缺乏产生环戊烷氧脂素的酶途径，例如茉莉酸、前列腺素或血栓烷。在细胞受到越来越多的过氧化氢 (HO) 的剂量时，我们通过 α-亚麻酸、花生四烯酸、二十碳五烯酸和二十二碳六烯酸的自由基过氧化作用，检测到非酶产生的异前列腺素，包括六种植物前列腺素、三种 F-异前列腺素、两种 F-异前列腺素和三种 F-神经前列腺素。HO 还触发了光合作用受损和 TAG 积累。F-植物前列腺素构成了检测到的主要类别（每 100 万个细胞 300 pmol；细胞内浓度约为 4 µm）。只有两种甘油磷脂，即磷脂酰胆碱和二酰甘油羟甲基三甲氨酸，才能为这些异前列腺素提供所有的底物。用九种合成异前列腺素处理 ，会产生在微摩尔范围内的效果，表现为 TAG 的积累和生长减缓，而不影响光合作用。因此，暴露于应激时 HO 和自由基的释放会导致甘油磷脂过氧化和非酶合成异前列腺素，从而抑制生长并通过未知的过程促进 TAG 积累的诱导。这种非酶氧化脂素在 中的特征描述开辟了一个研究领域，即在各种生理和环境背景下研究异前列腺素信号控制的过程。
