Subcellular localization of aflatoxin biosynthetic enzymes Nor-1, Ver-1, and OmtA in time-dependent fractionated colonies of Aspergillus parasiticus
Subcellular localization of aflatoxin biosynthetic enzymes Nor-1, Ver-1, and OmtA in time-dependent fractionated colonies of Aspergillus parasiticus
复制标题
DOI：
10.1007/s00203-003-0643-3
复制
发表时间：
2004-03-01
影响因子：
2.8
通讯作者：
Linz, JE
中科院分区：
文献类型：
--
作者：
Lee, LW;Chiou, CH;Linz, JE
寄生曲霉黄曲霉毒素的生物合成是一个复杂的过程，涉及至少18种途径酶的活性。这些酶在真菌菌落和真菌细胞中的分布还不清楚。本研究的目的是研究在黄曲霉毒素生物合成途径中分别代表早期、中期和晚期酶活性的NOR-1、Ver-1和OmtA的分布和亚细胞定位。对这三种酶在寄生曲霉SU-1中的分布进行了时间分级的72 h真菌菌落(组分1，48-72 h；组分2，24-48 h；组分3，0-24 h)的分析。Western印迹分析和免疫荧光显微镜显示菌落组分2中NOR-1、Ver-1和OmtA的丰度最高。NOR-1和Ver-1主要定位于细胞质，提示它们是胞浆酶。在细胞质中也可检测到OmtA。然而，在靠近菌落底部(底物)表面的细胞中，OmtA主要在初步鉴定为空泡的细胞器中检测到。这种细胞器在毒素生物合成中的作用尚不清楚。OMtA在细胞质或液泡状细胞器中的相对分布可能取决于真菌细胞的年龄和/或生理条件。
The biosynthesis of aflatoxin in Aspergillus parasiticus is a complex process that involves the activities of at least 18 pathway enzymes. The distribution of these enzymes within fungal colonies and fungal cells is not clearly understood. The objective of this study was to investigate the distribution and subcellular location of Nor-1, Ver-1, and OmtA, which represent early, middle, and late enzymatic activities, respectively, in the aflatoxin biosynthetic pathway. The distribution of these three enzymes within A. parasiticus SU-1 was analyzed in time-fractionated, 72-h fungal colonies (fraction 1, 48-72 h; fraction 2, 24-48 h; fraction 3, 0-24 h). Western blot analysis and immunofluorescence microscopy demonstrated the highest abundance of Nor-1, Ver-1, and OmtA in colony fraction 2. Fungal tissues in this fraction were analyzed by immunoelectron microscopy. Nor-1 and Ver-1 were primarily localized to the cytoplasm, suggesting that they are cytosolic enzymes. OmtA was also detected in the cytoplasm. However, in cells located near the basal (substrate) surface of the colony, OmtA was predominantly detected in organelles tentatively identified as vacuoles. The role of this organelle in toxin biosynthesis is unclear. The relative distribution of OmtA to the cytoplasm or to vacuole-like organelles may depend on the age and/or physiological condition of the fungal cells.