MudrB Function in Maize and Origin within the Grasses

突变子系统是玉米中一个高度诱变的转座子家族。突变体转座子受MuDR类转座子调控。MuDR元件编码两个基因：Mudra和MudrB。Mudra基因是一种可能的转座酶。虽然已知MudrB基因是Mu活性的必要组成部分，但其生化功能尚不清楚。本研究的主要目的是阐明该基因的进化和功能。MudrA基因在牧草中的分布比MudrB基因广泛得多。基于这一点，以及在许多表面上具有功能的MuDR样元件中没有MudrB，我们假设MudrB在这个转座子进化过程中的某个时候被MuDR捕获。为了验证这一假设，将对几种与玉米相关的牧草进行MudrB序列的存在和组成调查。为了研究MudrB在玉米中的功能，将利用现有的仅表达Mudra或仅表达MudrB的衍生物。这两个缺失衍生品将在基因上结合的实验将检验这两个可以相互补充的假设。此外，缺乏MudrB的衍生物将与影响突变子活性的突变交叉。为了确定在缺乏MUDR基因的物种中，MudrB是否有助于高水平的MuDR转座，将MudrB结构性和诱导性表达转化到水稻中。结合Mu元件TIR的蛋白质组学分析将被用来鉴定在存在或不存在Mudra或MudrB以及存在影响突变体活性的突变的情况下参与调节Mu元件转座的蛋白质。对这些突变的Mu末端结合的蛋白质组学分析也将有助于识别与影响活性的突变具有相同途径的其他蛋白质。

The Mutator system is a highly mutagenic family of transposable elements in maize. Mutator transposition is regulated by the MuDR class of transposons. MuDR elements encode two genes: mudrA and mudrB. The mudrA gene is the putative transposase. Although known to be a necessary component of Mu activity, the biochemical function of the mudrB gene is not known. The primary objective of this research is to elucidate the evolution and function of this gene. The mudrA gene is much more widely distributed among grasses than mudrB. Based on this, and the absence of mudrB in many apparently functional MuDR-like elements, it is hypothesized that mudrB was captured by MuDR at some point during the evolution of this transposon. To test this hypothesis, several grasses related to maize will be surveyed for the presence and composition of mudrB sequences. To investigate the function of mudrB in maize, existing derivatives that express only mudrA or only mudrB will be exploited. Experiments in which these two deletion derivatives will be combined genetically will test the hypothesis that the two can compliment each other. In addition, the derivative that lacks mudrB will be crossed to mutations that affect Mutator activity. In order to determine if mudrB can contribute to high levels of MuDR transposition in a species that lacks this gene, rice will be transformed with constitutively and inducibly expressed mudrB. Proteomic analysis of proteins binding Mu element TIRs will be employed to identify proteins involved in regulating Mu element transposition in the presence and absence of mudrA or mudrB and in the presence of mutations that affect Mutator activity. Proteomic analysis of binding of Mu termini from these mutations will also serve to identify other proteins that operate in the same pathway as the mutations that affect activity.