花是被子植物特有的生殖器官。花瓣是花的重要组成部分，具有重要的经济和文化价值。我们在前期研究中发现过表达拟南芥B3家族转录因子基因ABS2能使转基因拟南芥表现出花瓣缺失表型，而ABS2及其两个同源基因的三重功能缺失突变体出现花瓣数量增加表型。ABS2的强过表达系中出现类似cuc1cuc2双突变体的“杯状子叶”表型，并影响叶片中生长素的分布。这些结果暗示ABS2调控植物花瓣的发育并参与生长素稳态调控。本项目拟通过ABS2及其同源基因突变体的花瓣发育表型、ABS2基因在花瓣发育早期的精细表达模式分析、ABS2表达量变化对生长素在花分生组织中分布和运输的影响、ABS2与花器官和花瓣发育相关基因的遗传互作、ABS2相互作用蛋白的筛选以及ABS2靶点基因的筛选鉴定等研究，揭示ABS2调控植物花瓣发育的分子机制。本项目为阐明植物花器官发育的分子调控机理提供理论贡献，同时为人工调控花瓣数量提供新的途径。

Flower is the reproductive organ of angiosperms. As the most prominent part of the flower, petals are of great economic and cultural importance. In our previous work, we isolated an Arabidopsis B3 transcriptional factor gene ABS2. Over-expression of ABS2 led to a loss-of-petal phenotype, while triple loss-of-function mutants of ABS2 and its two closest homologous genes produced flowers with increased numbers of petals. In addition, ABS2 over-expression mutants showed abnormal auxin distributions in leaves as indicated by the expression of auxin reporter gene DR5-GUS. A “cup-shaped cotyledon” phenotype resembling the cuc1cuc2 double mutant was observed in strong ABS2 over-expression lines. These results suggest that ABS2 is involved in the regulation of petal development and auxin homeostasis. In this project, we propose to carry out the following experiments to further elucidate the functions of ABS2 in petal development. We will perform detailed analysis of petal phenotypes of both gain-of-function and loss-of-function mutants of ABS2 and its two homologous genes, and determine the expression patterns of ABS2 during early flower development. Furthermore, we will analyze auxin responses of ABS2 and determine the auxin localization and transport processes in the inflorescence meristem of ABS2 mutants. Finally, we will assess the genetic relationship between ABS2 and other flower and petal development related genes and determine the direct target genes of ABS2 using DEX/Cycloheximide (CHX) treatment and Chromatin Immuno-Precipitation (ChIP) experiments. Our results will not only gain new insight into the molecular mechanisms of petal development, but also provide new avenues for artificially engineering plant petal numbers in the future.