Cytological studies on the mechanism of hydrocarbon synthesis by a green alga, Botryococcus braunii

群居的绿藻布朗氏葡萄球菌产生异常高水平的碳氢化合物，占其干重的30%-60%，并在细胞表面积聚。通常，烃类合成发生在细胞分裂之后，多糖细胞壁形成之前。在本研究中，我们开发了一种诱导间期细胞进行活性烃合成的系统。活性烃合成发生在间期细胞（球质体）的细胞壁消化后，而不是通过去除已经积累的烃而发生。球质体的合成能力是正常间期细胞的12倍。球质体中高尔基体和反式高尔基网络（TGN）的形态与正常间期细胞的形态不同，而与刚分裂后的细胞形态相似。这一结果有力地支持了TGN参与烃合成的假设。然后，我们分离了编码β-COP的cDNA， β-COP是运输囊泡的外壳蛋白，介导通过高尔基体和TGN的囊泡运输。该cDNA编码一个947个氨基酸的蛋白质，预计分子质量为109 kDa。用抗β-COP抗体进行免疫电镜分析。为了制备布氏酵母球质体，我们对其细胞壁的多糖和糖成分进行了检测，明确布氏酵母具有特征性的球质体。

The colonial green alga Botryococcus braunii produces unusually high levels of hydrocarbons, amounting to 30%-60% of its dry weight, and accumulates them around the cell surfaces. Usually, the hydrocarbon synthesis occurrs just after cell division but before the formation of polysaccharide cell wall. In this study, we developed the induction-system of interphase cells into an active hydrocarbon synthesis. Active hydrocarbon synthesis occurred after the digestion of cell walls in interphase cells (spheroplasts), but didn't occur by the removal of already accumulated hydrocarbons. Maximally, we could induce 12 times of hydrocarbon synthesis by spheroplasts than those by normal interphase cells. The morphologies of Golgi bodies and the trans-Golgi networks (TGN) in spheroplasts were not similar to those in normal interphase cells, but those in cells just after cell division. The result strongly supports our hypothesis that the TGN is participated in the hydrocarbon synthesis. Then, we have isolated a cDNA coding for β-COP that is a coat-protein of transport vesicles mediating the vesicular transport through the Golgi apparatus and the TGN. The cDNA encodes a protein of 947 amino acids with a predicted molecular mass of 109 kDa. Immunoelectron microscopic analysis was also carried out with the anti-body against β-COP. To produce spheroplasts of B. braunii, we examined the polysaccharide and sugar compositions of the cell wall, and it was clarified that B.braunii had a characteristic one.