Characterization of a Green Microalga UTEX 2219-4: Effects of Photosynthesis and Osmotic Stress on Oil Body Formation

微藻是生質柴油的重要潛在來源之一。瞭解微藻的脂質合成之調控機制有助於生質柴油的生產管理。我們從UTEX 2219中分離出一株淡水綠藻並命名為UTEX 2219-4。以它的ITS序列做親緣關係研究，結果顯示這株綠藻與Scenedesmaceae科中物種較為相近。缺氮、高鹽及滲透壓逆境使UTEX 2219-4的脂質含量快速上升，而以缺氮及滲透壓逆境併用之效果最好。光合作用效率及葉綠素含量在缺氮下快速下降。在缺氮及黑暗中，UTEX 2219-4沒有油粒體形成。在缺氮及不飽和照度下，UTEX 2219-4的油粒體在200μmol/平方公尺s之下多於在100μmol/平方公尺s下，而DCMU阻斷了油粒體的形成。以上結果顯示生成油粒體的能源主要來自光合作用，而非從自噬作用的生理調節而來。

關鍵字

自噬作用；微藻；油粒體；滲透壓逆境；光合作用

並列摘要

Microalgae are an important potential feedstock for biodiesel production. Understanding the physiology of lipid biosynthesis in microalgae is pivotal to their management in aquaculture. A freshwater green microalgal strain, UTEX 2219-4, was isolated from UTEX 2219, which was reported to contain two strains. Its ITS sequences were closely related to those in the family Scenedesmaceae. Nitrogen starvation, salt stress and osmotic stress greatly enhanced lipid biosynthesis in this strain, while a combination of nitrogen deficiency and osmotic stress produced the most dramatic effects. Chloroplasts condensed and photosynthesis efficiency declined about 50% after 3 days of nitrogen starvation. Chlorophyll degradation followed the same trend but was more severe than the reduction of photosynthesis efficiency. Oil body formation was not observed in the cells kept in the dark under nitrogen starvation, suggesting that photosynthesis, rather than autophagy, is the main player in oil body formation. Under non-saturating light intensity levels coupled with nitrogen starvation, the oil body formation under 200 μmol/m^2s light intensity was more efficient than that under 100 μmol/m^2s. DCMU blocked both photosynthesis and oil body formation, again suggesting that photosynthesis, rather than autophagy, provides the energy for oil body formation during nitrogen starvation.

並列關鍵字

Autophagy ； Microalgae ； Oil body ； Osmotic stress ； Photosynthesis

國際替代計量

Characterization of a Green Microalga UTEX 2219-4: Effects of Photosynthesis and Osmotic Stress on Oil Body Formation

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