摘要：

旨在阐明油菜素内酯(BRs)在调控矮牵牛分枝发育的具体功能与机制。以矮牵牛为材料,通过外源激素处理、去顶试验、基因表达分析与转基因验证等方法,系统解析BR对分枝发育的调控作用。结果表明,外源BR不能直接解除顶端优势对腋芽萌发的抑制,但可显著促进腋芽伸长。BR与细胞分裂素(CK)在腋芽伸长阶段功能冗余,并与赤霉素(GA)协同增效。去顶处理迅速激活BR信号通路基因表达,其中PhBRI1和PhBZR1在去顶6 h后表达量分别上调4.2,9.5倍,24 h后分别上调34.3,51.4倍。克隆获得PhBZR1基因,该基因全长834 bp,编码277个氨基酸,含保守的BZR 结构域与核定位信号。组织特异性表达显示,PhBZR1在根中表达量最高。过表达PhBZR1能够显著增加植株分枝数,证实其正向调控分枝发育。揭示了BR通过PhBZR1介导的信号通路参与调控分枝发育,并阐明其与CK、GA的协同作用机制,为园艺作物株型改良提供了新的分子靶标与理论依据。

关键词: 矮牵牛, 油菜素内酯, 分枝发育, PhBZR1, 功能分析

Abstract:

This study aims to elucidate the specific functions and mechanisms of Brassinosteroids(BRs)in regulating branching development in Petunia hybrida cv.Mitchell Diploid.Using a combination of exogenous hormone application,decapitation experiments,gene expression analysis,and transgenic validation,it systematically investigated the regulatory role of BR in branching.The results showed that exogenous BR application did not overcome apical dominance to induce axillary bud outgrowth,but significantly promoted subsequent bud elongation.BR exhibited functional redundancy with cytokinin(CK)during bud elongation and acted synergistically with gibberellin(GA).Decapitation rapidly activated the expression of BR signaling pathway genes,with the transcript levels of PhBRI1 and PhBZR1 increasing by 4.2-fold and 9.5-fold at 6 hours post-decapitation,and further rising by 34.3-fold and 51.4-fold at 24 hours,respectively.The PhBZR1 gene was cloned,revealing a full-length sequence of 834 bp encoding 277 amino acids,containing a conserved BZR domain and a nuclear localization signal.Tissue-specific expression analysis indicated that PhBZR1 expression was highest in the roots.Overexpression of PhBZR1 significantly increased the branch number in transgenic plants,confirming its positive regulatory role in branching development.This study reveals that BR regulates branching through the PhBZR1-mediated signaling pathway and elucidates its synergistic mechanisms with CK and GA,providing a novel molecular target and theoretical foundation for improving plant architecture in horticultural crops.

Key words: Petunia hybrida, Brassinosteroid, Branching development, PhBZR1, Functional analysis

中图分类号: 

• S688.2