Lisch D R, Freeling M, Langham R J, Choy M Y
Department of Plant and Microbial Biology, 111 Koshland Hall, University of California, Berkeley, CA 94720, USA.
Plant Physiol. 2001 Mar;125(3):1293-303. doi: 10.1104/pp.125.3.1293.
Although the Mutator (Mu) system is well characterized in maize (Zea mays), very little is known about this highly mutagenic system of transposons in other grasses. Mutator is regulated by the MuDR class of elements, which encodes two genes, one of which, mudrA, has similarity to a number of bacterial transposases. Experiments in our laboratory, as well as database searches, demonstrate that mudrA sequences are ubiquitous and diverse in the grasses. In several species it is clear that multiple paralogous elements can be present in a single genome. In some species such as wheat (Triticum aestivum) and rice (Oryza sativa), mudrA-similar sequences are represented in cDNA databases, suggesting the presence of active Mu transposon systems in these species. Further, in rice and in sorghum, mudrA-like genes are flanked by long terminal inverted repeats, as well as the short host sequence direct repeats diagnostic of insertion. Thus, there is ample evidence that systems related to Mu in maize are at least potentially active in a wide variety of grasses. However, the mudrB gene, though important for Mu activity in maize, is not necessarily a component of Mu elements in other grasses.
尽管增变基因（Mu）系统在玉米（Zea mays）中已得到充分表征，但对于其他禾本科植物中这种高度诱变的转座子系统却知之甚少。增变基因受MuDR类元件调控，该类元件编码两个基因，其中一个基因mudrA与多种细菌转座酶具有相似性。我们实验室的实验以及数据库搜索表明，mudrA序列在禾本科植物中普遍存在且具有多样性。在几个物种中，很明显单个基因组中可能存在多个旁系同源元件。在一些物种如小麦（Triticum aestivum）和水稻（Oryza sativa）中，mudrA相似序列出现在cDNA数据库中，这表明这些物种中存在活跃的Mu转座子系统。此外，在水稻和高粱中，mudrA样基因两侧有长末端反向重复序列，以及插入所特有的短宿主序列直接重复序列。因此，有充分证据表明，与玉米中的Mu相关的系统在多种禾本科植物中至少具有潜在活性。然而，mudrB基因虽然对玉米中的Mu活性很重要，但不一定是其他禾本科植物中Mu元件的组成部分。
