School of Chemistry, University of Wollongong, NSW 2522, Australia; Laboratoire des Sciences de l'Environnement Marin (LEMAR), UMR 6539 CNRS UBO IRD IFREMER -Institut Universitaire Européen de la Mer, Technopôle Brest-Iroise, Rue Dumont d'Urville, 29280 Plouzané, France.
Institut de Biologie Physico-Chimique, Laboratory of Chloroplast Biology and Light Sensing in Microalgae, UMR 7141, Centre National de la Recherche Scientifique (CNRS), Sorbonne université, 75005 Paris, France.
Harmful Algae. 2021 Mar;103:101997. doi: 10.1016/j.hal.2021.101997. Epub 2021 Feb 18.
Allelopathy is an efficient strategy by which some microalgae can outcompete other species. Allelochemicals from the toxic dinoflagellate Alexandrium minutum have deleterious effects on diatoms, inhibiting metabolism and photosynthesis and therefore give a competitive advantage to the dinoflagellate. The precise mechanisms of allelochemical interactions and the molecular target of allelochemicals remain however unknown. To understand the mechanisms, the short-term effects of A. minutum allelochemicals on the physiology of the diatom Chaetoceros muelleri were investigated. The effects of a culture filtrate were measured on the diatom cytoplasmic membrane integrity (polarity and permeability) using flow-cytometry and on the photosynthetic performance using fluorescence and absorption spectroscopy. Within 10 min, the unknown allelochemicals induced a depolarization of the cytoplasmic membranes and an impairment of photosynthesis through the inhibition of the plastoquinone-mediated electron transfer between photosystem II and cytochrome bf. At longer time of exposure, the cytoplasmic membranes were permeable and the integrity of photosystems I, II and cytochrome bf was compromised. Our demonstration of the essential role of membranes in this allelochemical interaction provides new insights for the elucidation of the nature of the allelochemicals. The relationship between cytoplasmic membranes and the inhibition of the photosynthetic electron transfer remains however unclear and warrants further investigation.
化感作用是一些微藻能够与其他物种竞争的有效策略。来自有毒甲藻亚历山大藻的化感物质对硅藻具有有害影响，抑制代谢和光合作用，从而使甲藻具有竞争优势。然而，化感物质相互作用的精确机制和化感物质的分子靶标仍然未知。为了了解这些机制，研究了亚历山大藻化感物质对硅藻角毛藻生理的短期影响。使用流式细胞术测量了培养液对硅藻细胞质膜完整性（极性和通透性）的影响，并用荧光和吸收光谱法测量了光合作用性能。在 10 分钟内，未知的化感物质诱导细胞质膜去极化，并通过抑制质体醌介导的光系统 II 和细胞色素 bf 之间的电子传递来损害光合作用。在较长的暴露时间内，细胞质膜具有渗透性，光系统 I、II 和细胞色素 bf 的完整性受损。我们证明了膜在这种化感相互作用中的重要作用，为阐明化感物质的性质提供了新的见解。然而，细胞质膜与光合作用电子传递抑制之间的关系尚不清楚，需要进一步研究。
