Kroos L, Kaiser D
Department of Biochemistry, Stanford University School of Medicine, California 94305.
Genes Dev. 1987 Oct;1(8):840-54. doi: 10.1101/gad.1.8.840.
Certain developmental mutants of Myxococcus xanthus can be complemented extracellularly by wild-type cells. These mutants behave as if they are defective in cell-cell interactions that are required for development. There may be several different interactions because the mutants belong to four extracellular complementation groups (A, B, C, and D). We report here that B- and C- mutations change the pattern of gene expression during Myxococcus development as detected by transcriptional fusions to lacZ mediated by Tn5 lac. The mutant C locus reduced or abolished developmental beta-galactosidase expression from 15 lac fusions that normally begin to be expressed in wild-type cells after 6 hr of development. Expression of these C-dependent lac fusions was restored to C- mutants by adding wild-type cells. The C- mutation did not affect the expression of 10 lac fusions that normally begin to be expressed before 6 hr of development, indicating that the C-mediated cell-cell interaction is required beginning at about 6 hr of development. Cells require the B+ function very early in development because a B- mutation reduced or abolished developmental beta-galactosidase expression from all 26 lac fusions tested, including some that normally begin to be expressed at the onset of development. In a C- mutant and in a B- mutant, some lac fusions responded with reduced beta-galactosidase expression, whereas other fusions, which would normally begin beta-galactosidase expression at about the same time during development, expressed no beta-galactosidase, indicating that developmental genes within a given temporal class display different sensitivities to the absence of cell-cell interactions. Requirements for B+ and C+ function, as well as the previously described A+ function, appear to lie on the same developmental pathway.
黄色粘球菌的某些发育突变体可以被野生型细胞在细胞外互补。这些突变体的行为就好像它们在发育所需的细胞间相互作用方面存在缺陷。可能存在几种不同的相互作用，因为这些突变体属于四个细胞外互补组（A、B、C和D）。我们在此报告，通过Tn5 lac介导的与lacZ的转录融合检测发现，B和C突变会改变黄色粘球菌发育过程中的基因表达模式。突变的C位点降低或消除了15个lac融合基因的发育β-半乳糖苷酶表达，这些融合基因在野生型细胞发育6小时后通常开始表达。通过添加野生型细胞，这些依赖C的lac融合基因的表达恢复到C突变体中。C突变不影响10个lac融合基因的表达，这些融合基因通常在发育6小时之前开始表达，这表明C介导的细胞间相互作用在发育约6小时后才是必需的。细胞在发育的很早阶段就需要B +功能，因为B突变降低或消除了所有26个测试的lac融合基因的发育β-半乳糖苷酶表达，包括一些通常在发育开始时就开始表达的基因。在C突变体和B突变体中，一些lac融合基因的β-半乳糖苷酶表达降低而有反应，而其他融合基因，它们通常在发育过程中大约同一时间开始β-半乳糖苷酶表达，但却不表达β-半乳糖苷酶，这表明给定时间类别的发育基因对细胞间相互作用缺失表现出不同的敏感性。对B +和C +功能以及先前描述的A +功能的需求似乎位于同一条发育途径上。
