Developmentally Regulated Ac/Ds Transposition in Maize: The LAG1-0 Mutation

Weil9808880是一种罕见的玉米突变，Ac/DS生发逆转降低(LAG1-0)，并在本实验室得到了部分鉴定。它将被用来解决关于Ac/DS转座子切除频率的调节以及植物不同发育阶段如何影响它的具体问题。DS转座子诱导的等位基因在玉米胚乳中频繁恢复，通常在植物配子中从该籽粒恢复。但在LAG1-)的存在下，这些相同的DS等位基因萌发回复的频率比非突变的Lag1+植物低约100倍，而胚乳的回复保持不变。LAG1-0与9号染色体上的蜡质位点紧密连锁，是反式作用产物中的一个显性突变，并影响DS的切除，与AC转座酶的来源无关。随着发育的进展，LAG1-0抑制Ac/DS切除的程度在体细胞组织中变得更加严重。是否LAG1-0抑制在Ac/D上，特别是在发育开始时缓慢分裂的分生组织细胞中，将被测试。具体目标是：1)分离和鉴定LAG1-0突变，2)更清楚地定义在发育过程中Ac/DS切除被抑制的时间和地点，3)更清楚地定义参与抑制的遗传机制，4)确定调节这种不寻常的基因表达模式的其他基因和因素。高等植物的分生组织是由活跃分裂的相对未分化的细胞组成的圆顶状群体，最终是植物所有细胞的来源。这些细胞在发育过程中如何分化肯定是受基因表达调控的功能，但到目前为止，在分子水平上还不清楚。LAG1-0的突变特征表明，Ac或DS元件已插入到与这一过程相关的基因中，这一假说将通过进一步的实验来验证。这项研究的结果可以更深入地了解植物发育的分子机制。

Weil9808880An unusual maize mutation, Lowered Ac/Ds Germinal reversion (LAG1-0) has been identified and partially characterized in this laboratory. It will be used to address specific questions of the regulation of the frequency of Ac/Ds transposon excision and how it is affected by the different stages of development of the plant. Ds transposon-induced alleles that revert frequently in the endosperm of the maize typically revert frequently in gametes of the plant from that kernel. But in the presence of LAG1-), these same Ds alleles revert germinally about 100-fold less often than in non-mutant lag1+ plants, while reversion in endosperm remains unchanged. LAG1-0 is tightly linked to the waxy locus on chromosome 9, is a dominant mutation in a trans-acting product and affects Ds excision regardless of Ac transposase source. The degree to which LAG1-0 suppresses Ac/Ds excision becomes more severe in somatic tissues as development progresses. Whether LAG1-0 suppression is imposed on Ac/Ds specifically in the slowly dividing cells of the meristem at the beginning of development will be tested. The specific aims are: 1) to isolate and characterize the LAG1-0 mutation, 2) to define more clearly when and where in development the suppression of Ac/Ds excision occurs, 3) to more clearly define the genetic mechanisms involved in the suppression, 4) to identify other genes and factors that regulate this unusual pattern of gene expression.Meristems of higher plants are dome-shaped populations of actively dividing, relatively undifferentiated cells that are, ultimately, the source of all cells in the plant. How these cells become differentiated during development must be a function of regulated gene expression but it is, as yet, not understood at the molecular level. The LAG1-0 mutation characteristics suggest that an Ac or Ds element has inserted into a gene relevant to this process and this hypothesis will be tested by further experimentation. The results of this study could provide greater insight into the molecular mechanisms involved in plant development.