Dooner H K, English J, Ralston E J
Advanced Genetic Sciences, Oakland, CA 94608.
Mol Gen Genet. 1988 Mar;211(3):485-91. doi: 10.1007/BF00425705.
The maize mutable allele bz-m2 (Ac), which arose from insertion of the 4.6 kb Ac element in the bz (bronze) locus, gives rise to stable bz (bz-s) derivatives that retain an active Ac element closely linked to bz. In the derivative bz-s: 2114 (Ac), the Ac element is recombinationally inseparable from bz and transposes to unlinked sites at a frequency similar to that in the progenitor allele bz-m2 (Ac). Both alleles have been cloned and sequenced. The bz-s: 2114 (Ac) mutation retains Ac at the original site of insertion, but has lost a 789 bp upstream bz sequence adjacent to the insertion, hence the stable phenotype. The 8 bp target site direct repeat flanking the Ac insertion in the bz-m2 (Ac) allele is deleted in bz-s: 2114 (Ac), yet the Ac element is not impaired in its ability to transpose. The only functional Ac element in bz-s: 2114 (Ac) is the one at the bz locus: in second-cycle derivatives without Ac activity, the loss of Ac activity correlated with the physical loss of the Ac element from the bz locus. The deletion endpoint in bz-s: 2114 (Ac) corresponds exactly with the site of insertion of a Ds element in a different bz mutation, which suggests that there may be preferred integration sites in the genome and that the deletion originated as the consequence of an abortive transposition event. Finally, we report two errors in the published Ac sequence.
玉米的突变等位基因bz-m2（Ac）源于4.6 kb的Ac元件插入到bz（青铜色）基因座中，它产生了稳定的bz（bz-s）衍生物，这些衍生物保留了与bz紧密连锁的活性Ac元件。在衍生物bz-s:2114（Ac）中，Ac元件与bz在重组时不可分离，并以与祖代等位基因bz-m2（Ac）相似的频率转座到不连锁的位点。这两个等位基因都已被克隆和测序。bz-s:2114（Ac）突变在插入的原始位点保留了Ac，但在插入位点相邻的上游丢失了789 bp的bz序列，因此呈现稳定的表型。bz-m2（Ac）等位基因中Ac插入两侧的8 bp靶位点直接重复序列在bz-s:2114（Ac）中缺失，但Ac元件的转座能力并未受损。bz-s:2114（Ac）中唯一具有功能的Ac元件位于bz基因座：在没有Ac活性的第二代衍生物中，Ac活性的丧失与Ac元件从bz基因座的物理丢失相关。bz-s:2114（Ac）中的缺失终点与不同bz突变中Ds元件的插入位点完全对应，这表明基因组中可能存在优先整合位点，并且该缺失是由一次失败的转座事件导致的。最后，我们报告了已发表的Ac序列中的两个错误。
