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

CLC Number: 

• S688.2