Levy A A, Britt A B, Luehrsen K R, Chandler V L, Warren C, Walbot V
Department of Biological Sciences, Stanford University, California 94305-5020.
Dev Genet. 1989;10(6):520-31. doi: 10.1002/dvg.1020100611.
The regulation of excision of Mu elements of the Mutator transposable element family of maize is not well understood. We have used somatic instability of Mu receptor elements from the Bronze 1 and Bronze 2 loci to monitor the frequency and the timing of excision of Mu elements in several tissues. We show that spot size in the aleurone of a bz2::mu1 stock varies between one to approximately 256 cells. This indicates that excision events begin eight divisions prior to full aleurone differentiation and end after the last division of the aleurone. We show that excision is equally biased for late events in all other tissues studied. A locus on chromosome 5 has been identified that affects spot size, possibly by altering the timing of Mu excision. Using somatic excision as an assay of Mutator activity, we found that activity can change in small sectors of the tassel; however, there are no overall activity changes in the tassel during the period of pollen shedding. We also report the recovery of germinal revertants for the bz1::mu1 and bz2::mu1 alleles. One of these revertant alleles was characterized by Southern blot analysis and found to be similar to the progenitor of the mutable allele.
玉米Mutator转座因子家族中Mu元件切除的调控机制尚未完全明确。我们利用来自青铜1和青铜2位点的Mu受体元件的体细胞不稳定性，来监测Mu元件在几种组织中的切除频率和时间。我们发现，bz2::mu1株系糊粉层中的斑点大小在1到约256个细胞之间变化。这表明切除事件在糊粉层完全分化前8次分裂开始，并在糊粉层最后一次分裂后结束。我们发现，在所有其他研究的组织中，切除事件同样倾向于晚期发生。已在5号染色体上鉴定出一个位点，它可能通过改变Mu切除的时间来影响斑点大小。利用体细胞切除作为Mutator活性的检测方法，我们发现雄穗的小区域内活性会发生变化；然而，在花粉散落期间，雄穗的整体活性没有变化。我们还报告了bz1::mu1和bz2::mu1等位基因的生殖系回复体的获得情况。其中一个回复体等位基因通过Southern印迹分析进行了表征，发现与可变等位基因的祖先相似。
