Walbot V
Department of Biological Sciences, Stanford University, CA 94305-5020.
Mol Gen Genet. 1992 Sep;234(3):353-60. doi: 10.1007/BF00538694.
After epigenetic loss of Mutator activity, the family of Mu elements in Zea mays becomes immobile and highly methylated; in addition, Mu9, the presumptive autonomous regulatory element, is transcriptionally silent and its copy number decreases in successive crosses to non-Mutator lines. Spontaneous reactivation, scored as restoration of somatic instability of potentially mutable alleles of Bronze-2, of such cryptic Mutator lines is rare, occurring with a frequency of about 10(-4). Irradiation of pollen with 254 nm ultraviolet light increases reactivation rate in the progeny kernels by up to 40-fold. Accompanying reactivation, the copy number of Mu9 elements increased, two-fold in one line and 20 to 40-fold in a second line. Reactivation may involve direct DNA damage or immediate physiological stress in the treated pollen.
在Mutator活性发生表观遗传丧失后，玉米中的Mu元件家族变得不可移动且高度甲基化；此外，假定的自主调控元件Mu9转录沉默，并且在与非Mutator品系的连续杂交中其拷贝数减少。这种隐性Mutator品系的自发重新激活（以青铜2潜在可变等位基因的体细胞不稳定性恢复来衡量）很罕见，发生频率约为10^(-4)。用254纳米紫外线照射花粉可使后代籽粒中的重新激活率提高多达40倍。伴随重新激活，Mu9元件的拷贝数增加，在一个品系中增加了两倍，在另一个品系中增加了20至40倍。重新激活可能涉及处理过的花粉中的直接DNA损伤或即时生理应激。
