Meristem Identity Genes and the Evolution of Plant Architecture in Brassicaceae

植物的发育受分生组织控制，分生组织是有组织的细胞分裂和分化的区域。根据一组分生组织特征基因的活性，茎分生组织可以具有花或营养的特征。由于花终止了新梢的生长，花的分布以及分生组织特征基因的调节，可能会对植物的结构产生深远的影响。因此，有人假设，物种之间的结构差异在很大程度上是由分生组织特征基因的变化驱动的。在拟议的工作中，我们将评估三个分生组织特征基因LFY、TFL1和AP1在解释为什么芥菜/甘蓝科(十字花科)的三种植物在基生莲座花而不是在拉长的无叶茎(花序)上开花的作用。在之前的工作中，PI研究了三种莲座花开花物种的LFY基因，Ionopsidium acaule(Ia)，Idahoa sigigera(IS)和Levenworth ia crassa(LC)。他们通过转化将这三个物种的LFY基因导入了花序开花物种拟南芥(Arabiopsis Thaliana)的植物中(该物种缺乏功能性的内源LFY拷贝)。他们发现，虽然Ia-LFY对植物的构型没有影响，但IsLFY和LcLFY基因往往会诱导对植物构型的修改，使人想起莲座花，但它们不会导致完全转化为莲座花。这一结果表明，LFY基因座的进化变化促进了这些物种的莲座花的平行进化，但指向了额外的、尚未确定的遗传变化。拟议的工作将包括LFY的后续实验，旨在确定物种之间的重要差异是位于蛋白质编码区还是位于邻近的调控DNA。将对AP1和TFL1进行类似的实验，以确定它们是否对莲座花的进化起到了作用。具体地说，我们的目标是阐明这些基因的分子进化，并将它们从莲座花物种转移到拟南芥中，看看它们是否可以单独或与外源LFY基因一起诱导莲座花。这项拟议的研究将阐明DNA的进化变化如何转化为现存物种的形态差异。特别是，这项工作将澄清：(1)遗传变化集中在一小部分发育基因中的程度，(2)蛋白质相对于调节变化的相对重要性，以及(3)独立谱系中的平行进化在多大程度上使用相同的遗传工具箱。此外，对植物结构如何调控的具体理解最终可能对修改作物以促进更高的生产力和更容易收获的努力具有重要意义。这项研究将有助于培养一名研究生和一名博士后科学家。

0234118BaumThe development of plants is controlled by meristems, areas of organized cell division and differentiation. Shoot meristems can take on either a floral or vegetative identity depending upon the activity of a set of meristem identity genes. Because flowers terminate shoot growth, the distribution of flowers, and hence the regulation of meristem identity genes, may have a profound affect upon plant architecture. Thus, it has been hypothesized that the architectural differences between species are largely driven by changes in meristem identity genes. In the proposed work we will evaluate the role of three meristem identity genes, LFY, TFL1, and AP1, in explaining why three species of the mustard/cabbage family (Brassicaceae) produce flowers from the basal rosette of leaves rather than on an elongated leafless stem (the inflorescence).In previous work the PI studied LFY genes from three rosette flowering species, Ionopsidium acaule (Ia), Idahoa scapigera (Is), and Leavenworthia crassa (Lc). They used transformation to introduce LFY genes from these three species into plants of an inflorescence flowering species, Arabidopsis thaliana (that lacked a functional endogenous copy of LFY). They found that whereas Ia-LFY had no affect on plant architecture, the IsLFY and LcLFY genes tended to induce modifications to plant architecture reminiscent of rosette flowering, but they did not cause complete conversion to rosette flowering. This result suggests that evolutionary changes at the LFY locus contributed to the parallel evolution of rosette flowering in these species, but point to additional, as yet unidentified, genetic changes. The proposed work will include follow-up experiments on LFY aimed at determining whether the important differences between species are located in the protein-coding region or the adjacent regulatory DNA. Similar experiments with AP1 and TFL1 will be done to see if they may have contributed to the evolution of rosette flowering. Specifically, the goal is to clarify the molecular evolution of the genes and move them from the rosette flowering species into A. thaliana to see if they can induce rosette-flowering individually or jointly with the exogenous LFY genes.This proposed study will shed light on how evolutionary changes in DNA translate into difference in the morphology of living species. In particular, the work will clarify: (1) the extent to which genetic changes are concentrated in a small set of developmental genes, (2) the relative importance of protein versus regulatory changes, and (3) the extent to which parallel evolution in independent lineages uses the same genetic toolbox. Additionally, the specific understanding of how plant architecture is regulated could ultimately have significance for efforts to modify crop plants to facilitate higher productivity and easier harvesting.The research will contribute to the training of one graduate student and one postdoctoral scientist.