Dimerization of Floral Organ Identity Proteins in Arabidopsis

相当多的证据支持这一假设，即控制不同开花植物物种花发育的基因产物和机制在很大程度上是保守的。 许多植物发育控制蛋白含有称为MADS结构域的保守DNA结合结构域。 拟南芥中的MADS家族由30多个基因组成。 MADS蛋白参与植物发育的多个方面，包括开花时间控制、分生组织特化、花器官特性和果实发育。 尽管这些MADS蛋白在植物发育中的重要性，但人们对这些蛋白如何发挥功能和相互作用知之甚少。 本论文主要研究拟南芥花器官识别MADS蛋白APETALA 3（AP 3）和PISTILLATA（PI）。 AP 3和PI在拟南芥花中起着指导花瓣和雄蕊发育的作用。 所有的MADS蛋白都以异二聚体或同二聚体的形式与DNA结合。 拟南芥中的大多数MADS蛋白能够与多种伴侣蛋白形成同源二聚体和异源二聚体。 相比之下，AP 3和PI不能同源二聚化并形成专性异源二聚体。 AP 3/PI异源二聚体是高度特异性的，并且在进化上是保守的，如在远亲植物物种金鱼草中的AP 3和PI同源物之间的类似相互作用所证明的。 该项目的重点是确定氨基酸和亚结构域的AP 3和PI蛋白介导的高度特异性的异源二聚体之间的相互作用AP 3和PI，这将通过位点特异性诱变和利用“反向”酵母双杂交方法。 通过这项研究，我们希望能够确定这类重要的植物发育调节剂的二聚体的规则。这项研究的第二个焦点集中在PI的一个不寻常的等位基因上，称为PI-5。 与所有其他ap 3和pi突变体不同，pi-5-仅在花的单轮中表现出表型缺陷。 PI-5蛋白在与野生型AP 3伴侣蛋白的蛋白质-蛋白质相互作用中表现出缺陷。 PI-5的遗传实验表明，螺旋特异性因子调节PI-5的活性。 同时使用遗传和分子的方法，影响花器官特性的轮特异性因素将被分离和表征。

Considerable evidence supports the hypothesis that the gene products and mechanisms that control flower development in different flowering plant species are largely conserved. Many plant developmental control proteins contain a conserved DNA binding domain called the MADS domain. The MADS family in Arabidopsis consists of more than 30 genes. MADS proteins are involved in diverse aspects of plant development including flowering time control, meristem specification, floral organ identity, and fruit development. Despite the importance of these MADS proteins in plant development, little is known about how these proteins function and interact. This proposal focuses on the floral organ identity MADS proteins APETALA3 (AP3) and PISTILLATA (PI) in Arabidopsis thaliana. AP3 and PI function to direct the development of petal and stamens in the Arabidopsis flower. All MADS proteins bind to DNA either as heterodimers or homodimers. Most MADS proteins in Arabidopsis are capable of forming both homodimers and heterodimers with a variety of partner proteins. AP3 and PI, by contrast, are unable to homodimerize and form an obligate heterodimer. The AP3/PI heterodimer is highly specific and is evolutionarily conserved as evidenced by a similar interaction between the AP3 and PI homologs in the distantly related plant species Antirrhinum majus. This project is focused on identifying the amino acids and subdomains in the AP3 and PI proteins that mediate the highly specific heterodimer interaction between AP3 and PI; this will be done both by site-specific mutagenesis and by utilizing "reverse" yeast two-hybrid approaches. Through this research, we hope to be able to define the rules for dimerization of this importance class of plant developmental regulators. A second focus of this research centers on an unusual allele of PI called pi-5. Unlike all other ap3 and pi mutants, pi-5- exhibits phenotypic defects only in a single whorl of the flower. The PI-5 protein exhibits defects in protein-protein interaction with a wild-type AP3 partner protein. Genetic experiments with pi-5 suggest that whorl-specific factors modulate the activity of PI-5. Using both genetic and molecular approaches, whorl-specific factors that affect floral organ identity will be isolated and characterized.