Molecular and Genetic Studies on Maize Transposable Elements-- Paramutation and Directed Transposition

玉米Ac-DS系统的转座元件之间的新的相互作用将被研究。初步研究表明，DS元件与同源染色体上的Ac-w衍生物之间存在相互作用或某种形式的信息传递。一条染色体上存在高度甲基化的wx-m9ds-Cy元件，导致同源物上遥远位置的Ac-w元件发生类似于参数突变的失活和甲基化。在每个杂合子中，Wx-M6、Wx-M9中的ds元件和染色体II 9上标准位置的ds状态不是失活的，而是使Ac-w沿着其染色体移动，并重新插入到同源物上ds元件所占据的位置。Wx-M1等位基因中的小DsI元件不起反式作用，必须位于同一染色体上才能影响Ac-w的迁移。分子证据表明Ac-w基因被重新插入到Wx-M1基因中。这些相互作用仅限于同源染色体上的元件。这些研究将得到扩展，并将通过遗传和分子分析来研究相互作用。虽然在分子水平上已经知道了许多关于转座元件的知识，但这项研究是第一次表明定向转座和定点插入可以而且确实发生了。该项目的继续将使人们能够收集更多的信息，以期在试图了解正常、非胁迫的玉米基因组中的转座元件执行什么功能(如果有的话)方面取得潜在突破。

Novel interactions between the transposable elements of the Ac-Ds system in maize will be investigated. Preliminary studies indicate interaction or some form of information transfer between Ds elements and Ac-w derivatives on homologous chromosomes. The presence of the highly methylated wx-m9Ds-cy element on one chromosome leads to the paramutation-like inactivation and methylation of an Ac-w element at a distant position on the homologue. The Ds elements in wx-m6, wx-m9 and the State I Ds in standard position on chromosome II 9 do not inactivate but, in every heterozygote, cause Ac-w to move along its chromosome and be reinserted at the site occupied by the Ds element on the homologue. The small Ds I element in the wx-m1 allele does not act in trans and must be on the same chromosome to effect the migration of Ac-w. Molecular evidence indicates that Ac-w is reinserted in the wx-m1 gene. These interactions are limited to elements on homologous chromosomes. These studies will be extended and the interactions by genetic and molecular analyses wil be investigated. While much is known about transposable elements on the molecular level, this study is the first to suggest that directed transposition and site-specific insertion can and does occur. The continuation of this project will allow further information to be gathered on what could be a potential breakthrough on attempts to understand what, if any, function is performed by transposable elements in the normal, non-stressed genome of corn.