柴胡(Bupleurum spp.)以根入药，其侧根分支多少与柴胡产量、药效成分含量及商品性密切相关。对拟南芥、水稻及玉米等植物研究表明Aux/IAA基因通过调节生长素极性运输对植物侧根位点发生位置及侧根初始化起主要调控作用。本研究拟分析柴胡不同基因型（北柴胡品种川北柴1号及狭叶柴胡品种中红柴1号）的根系形态差异及其组织结构基础，通过组织特异性表达分析及外施IAA对Aux/IAA基因的应答模式，筛选并克隆影响柴胡侧根形成的Aux/IAA关键基因。通过转化拟南芥突变体及在中红柴1号中超量表达以分析Aux/IAA基因在柴胡中的生物学功能；克隆Aux/IAA基因启动子，并分析该启动子的组织特异性。本研究将揭示柴胡侧根分支差异的结构及分子基础，为柴胡根系改良提供理论依据。

Root branching is very important for yield, medicinal ingredients content and commercial quality to Bupleurum species, because their roots are used as herbal drugs. Previous studies of root branching in Arabidopsis, rice, and maize indicated that Aux/IAA genes can regulate polar auxin transport to controls prebranch site formation and lateral root initiation. In the present project, root branching and histological analyses will be performed among two commercial varieties of ChuanbeichaiNo. 1 (Bupleurum chinense DC) and Zhonghongchai No. 1 (B. scorzonerifolium Willd). The expression patterns of Aux/IAA genes in different tissues, and the Aux/IAA genes expression change associated with exogenous IAA treatment will be analyzed to identify the key genes can regulate root branching in Bupleurum. Arabidopsis transformation and gene overexpression in Zhonghongchai No. 1 will be conducted to verify the key role of candidate genes. In addition, the promoters of these Aux/IAA genes will be cloned and their tissue specificity will be analyzed in our study. This study will advance our understanding about histological and molecular mechanisms, and provide theoretical basis for root branching improvement in Bupleurum.