Molecular analysis of the maize wx-B3 allele indicates that precise excision of the transposable Ac element is rare.
Molecular analysis of the maize wx-B3 allele indicates that precise excision of the transposable Ac element is rare.
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玉米 wx-B3 等位基因的分子分析表明，转座 Ac 元件的精确切除很少见。
DOI：
10.1093/genetics/130.2.377
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发表时间：
1992
期刊：
影响因子：
3.3
通讯作者：
Wessler,S
中科院分区：
文献类型：
--
作者：
Baran,G;Echt,C;Bureau,T;Wessler,S
玉米wx-B3突变的体细胞和萌发行为表明该Ac等位基因很少恢复。含有Wx - b3的胚乳显示微小且不常见的Wx逆转扇区，而用I/KI染色Wx - b3花粉时未检测到明显的逆转。先前对其他转座因子等位基因很少恢复的研究暗示了低水平的元件切除。与其他等位基因不同，Wx - b3 Ac元件的结构和从Wx基因转座或反式激活Ds元件的能力与完全活性的Ac元件难以区分。体细胞和生发切除事件的特征使我们得出结论，wx-B3 Ac元件的切除几乎总是产生零等位基因。此外，wx-B3突变在物理图谱和遗传图谱上的位置之间的良好相关性表明，Ac插入是wx-B3的唯一病变。因此，精确切除这个Ac应该可以恢复Wx功能。相反的部分和花粉粒是罕见的，这表明精确切除Ac也是罕见的。无论wx- b3是半合子还是在具有野生型插入位点的wx等位基因上，wx- b3的逆转频率是相当的，这一发现说明了Ac和果蝇P元件的切除机制之间的根本差异。
The somatic and germinal behavior of the maize wx-B3 mutation indicates that this Ac allele rarely reverts. Endosperms containing wx-B3 display tiny and infrequent Wx revertant sectors while no significant reversion is detected when wx-B3 pollen is stained with I/KI. Previous studies of other transposable element alleles that revert infrequently have implicated low levels of element excision. Unlike these other alleles, the wx-B3 Ac element is indistinguishable from fully active Ac elements with respect to its structure, and its ability to transpose from the Wx gene or to trans-activate a Ds element. Characterization of somatic and germinal excision events lead us to conclude that excision of the wx-B3 Ac element almost always produces null alleles. Furthermore, the excellent correlation between the position of the wx-B3 mutation on the physical and genetic maps indicates that the Ac insertion is the only lesion of wx-B3. As a result, precise excision of this Ac should restore Wx function. The fact that revertant sectors and pollen grains are rare indicates that precise excision of Ac is also rare. The finding that the wx-B3 reversion frequency is comparable whether wx-B3 is hemizygous or over a wx allele with a wild-type insertion site illustrates a fundamental difference between the excision mechanisms of Ac and Drosophila P elements.