Mechanism and role of inositol phospholipid turnover in yeast morphogenesis

本课题的研究结果表明，热带假丝酵母Pk 233在乙醇培养基中以丝状形式生长，肌醇可以抑制乙醇诱导的形态学变化，而在对数生长期，肌醇的磷脂周转率增加，本研究旨在阐明肌醇磷脂周转在真菌二型性中的作用。结果表明：（1）钙离子载体A23187代替乙醇加入到培养基中，能引起丝状菌的生长。通过同时添加合成的二酰基甘油，1-油酰基-2-乙酰基甘油，增强了这种效果。发现佛波酯，12-0-十四酰基-佛波醇-13-乙酸酯（TPA）对于刺激A23187的作用非常有效。这些结果将提供证据肌醇磷脂营业额参与丝状生长的发生。(2)通过SDS-聚丙烯酰胺凝胶电泳检测细胞匀浆中蛋白质的存在，蛋白质的细胞内容物可能与乙醇诱导的丝状生长和肌醇磷脂周转相关地变化，所述细胞匀浆来自在没有添加乙醇（对照）、添加乙醇、添加乙醇加肌醇和添加A23187加TPA的情况下生长至对数期的细胞。(3)在与乙醇诱导的丝状生长，环AMP的细胞含量显着增加，这表明已经建立在更高的真核细胞的两个信号转导途径将采取一致行动，以诱导这种微生物的丝状生长。(4)乙醇也引起酿酒酵母中的丝状生长。这一发现为揭示肌醇磷脂周转在形态发生中的普遍意义提供了线索，并为利用遗传学方法研究肌醇磷脂周转的调控机制提供了便利。

Our previous studies revealed that Candida tropicalis Pk233 grows in filamentous form in ethanol-supplemented medium and myo-inositol prevents the ethanol-induced morphological change,and that cells grown with ethanol to the log phase exhibits an increased rate of phosphatidylinositol turnover.This research project was designed to clarify the role of inositol phospholipid turnover in fungal dimorphism. The results obtained are as follows: (1) A calcium ionophore, A23187, caused filamentous growth when added to growth medium in place of ethanol. This effect was enhanced by concomitant addition of synthetic diacylglycerol, 1-oleoyl-2-acetylglycerol. A phorbol ester, 12-0-tetradecanoyl-phorbol-13-acetate (TPA) was found to be much potent for stimulating the effect of A23187. These results would provide evidence for the involvement of inositol phospholipid turnover in the occurrence of filamentous growth. (2) The presence of proteins whose cellular contents may vary in association with the ethanol-induced filamentous growth and with inositol phospholipid turnover was detected by SDS-polyacrylamide gel electrophoresis of proteins in the homogenates from cells which had been grown to the log phase with no added ethanol (control), with ethanol, with ethanol plus myo-inositol and with A23187 plus TPA. (3) In association with the ethanol-induced filamentous growth, cellular content of cyclic AMP was markedly increased, suggesting that the two signal transduction pathways which have been established in higher eucaryotic cells would act in concert to induce filamentous growth of this microorganism. (4) Ethanol caused filamentous growth also in Saccharomyces cerevisiae. This finding would provide a clue to general significance of inositol phospholipid turnover in morpho-genesis and promote the investigation on regulatory mechanism of the turnover with the ease of applying genetic approaches.