Dotson W D, Tove S R, Parks L W
Department of Microbiology, North Carolina State University, Raleigh 27695-7615, USA.
Lipids. 2000 Mar;35(3):243-7. doi: 10.1007/s11745-000-0519-9.
Phytophthora species are eukaryotic sterol auxotrophs that possess the ability to grow, albeit poorly, in the complete absence of sterols. Growth of Phytophthora is often improved substantially when an exogenous source of sterol is provided. Additionally, sterols may be required for sexual and asexual sporulation in Phytophthora. Our research has been focused on identifying and characterizing the immediate physiological effects following sterol addition to cultures of P. parasitica. Through gas chromatographic analysis of extracts from P. parasitica cultures that were fed various sterols, we have obtained evidence for sterol C5 desaturase and delta7 reductase activities in this organism. Zoo blots were probed with DNA sequences encoding these enzymes, from Saccharomyces cerevisiae and Arabidopsis thaliana. Hybridization of a S. cerevisiae ERG3 probe to P. parasitica DNA was observed, implicating sequence similarity between the sterol C5 desaturase encoding genes. Differential display experiments, using RNA from P. parasitica, have demonstrated a pattern of altered gene expression between cultures grown in the presence and absence of sitosterol. Characterization of sterol-related metabolic effects and sterol functions in Phytophthora should lead to improved measures for control of this important group of plant pathogens.
疫霉属物种是真核生物固醇营养缺陷型，即使在完全没有固醇的情况下也具备生长能力，不过生长状况不佳。当提供外源固醇时，疫霉的生长通常会显著改善。此外，固醇可能是疫霉有性和无性孢子形成所必需的。我们的研究重点是确定并描述向寄生疫霉培养物中添加固醇后产生的直接生理效应。通过对喂食了各种固醇的寄生疫霉培养物提取物进行气相色谱分析，我们获得了该生物体中固醇C5去饱和酶和δ7还原酶活性的证据。用来自酿酒酵母和拟南芥的编码这些酶的DNA序列对动物杂交印迹进行探测。观察到酿酒酵母ERG3探针与寄生疫霉DNA杂交，这表明固醇C5去饱和酶编码基因之间存在序列相似性。使用寄生疫霉的RNA进行差异显示实验，结果表明在有和没有谷甾醇的情况下培养的培养物之间存在基因表达改变的模式。对疫霉中与固醇相关的代谢效应和固醇功能进行表征，应该能够改进对这一重要植物病原体群体的控制措施。
