The study on the locus regulating the cell polarity in axenic strains of the cellular slime mold

细胞核和微管组织中心(MTOC)定义了主要细胞相对于细胞顶轴-基轴或前轴-后轴的极性。研究发现，MTOC在聚集盘基盘基菌中的定位受遗传调控。所有被检查的野生型菌株都显示出类似的细胞极性，如MTOC.2之前的核排列所定义的那样。相反，在AX2和AX3中，在连锁群II和III上携带无菌突变的无菌菌株中，MTOC位于核的前面。含有无菌连接组II而不含III组的细胞将MTOC定位在细胞核的前面。相反，具有无菌连接基团III而不是II的菌株将其定位在核的后面。因此，无菌连接基团II负责将MTOC定位在核的前面。在AX3中，3个隐性突变axeC、OAAA和daxA被归入无性连锁群II。然而，OAAA和DaxA的表型与MTOC的前位无关。因此，AXeC可能对无菌生长和MTOC定位具有多效性，或者其他尚未确定的连锁基因(S)可能负责MTOC的前定位。野生型NC-4细胞可能有一个基本的机制，调节MTOC在细胞核后面或前面的位置。链龄II组的S基因可能会在无菌菌株中发生突变，以刺激MTOCs的前位或阻止MTOCs的后位。对微管相关蛋白进行CBB染色的SDS-PAGE分析表明，与NC-4相比，定位于核前的MTOC菌株在116和170-190kd处的条带增加。

The nucleus and the microtubule-organizing center (MTOC) are though to define major cell polarity with respect to an apical-basal or anterior-posterior axis of cells. Positioning of the MTOC in aggregating Dictyostelium discoideum was found to be genetically regulated.1. All wild-type strains examined showed similar cell polarity, as defined by the alignment of the nucleus in advance of the MTOC.2. On the contrary, in Ax2 and Ax3, axenic strains carrying axenic mutations on linkage groups II and III, the MTOC was located ahead of the nucleus.3. Cells containing axenic linkage group II but not III positioned the MTOC ahead of the nucleus. Conversely strains having axenic linkage group III but not II positioned it posterior to the nucleus. Thus the axenic linkage group II is responsible for the location of the MTOC anterior to the nucleus.4. Three recessive mutations, axeC, oaaA and daxA, are assigned to axenic linkage group II in Ax3. However, phenotypes of oaaA and daxA did not correlate with anterior position of the MTOC. Therefore, axeC may have pleiotropic effects on axenic growth and MTOC positioning, or other linked gene(s) not yet identified may be responsible for anterior positioning of the MTOCs.6. Wild-type NC-4 cells probably have a basal machinery regulating the position of the MTOC either behind or ahead of the nucleus. Gene(s) in link-age group II may mutate in axenic strains in order to stimulate anterior position or to prevent posterior positioning of the MTOCs.7. When microtubule-related proteins were analyzed on SDS-PAGE stained with CBB, bands at 116 and 170-190 kd increased in the strain positioning the MTOC anterior to the nucleus compared with those in NC-4.