[Functional analysis of PhPIF4 in Petunia hybrida branching development]

As a core regulatory component of photomorphogenic signaling, phytochrome interacting factor 4 (PIF4) participates in multiple developmental processes in plants. To analyze the function and mechanism of this gene in ornamental plants, this study elucidated the role of PhPIF4 in the branching development of Petunia hybrida and its downstream regulatory pathways through genetic transformation and RNA sequencing (RNA-seq). The results showed that Arabidopsis transgenic lines overexpressing PhPIF4 exhibited reduced branches, whereas PhPIF4-RNAi transgenic lines of P. hybrida displayed significantly increased branches. RNA-seq results revealed that 591 differentially expressed genes in PhPIF4-overexpressing lines were significantly enriched in phytohormone metabolic pathways, and the expression levels of cytokinin biosynthesis-related genes IPT3/5, CYP735A1, and LOG2 were markedly downregulated. Further verification demonstrated that PhPIF4 affected branching by activating the branching inhibitor genes BRC1 and SPL9 and the far-red light chaperone gene FHL. This study provides a theoretical basis for further elucidating the molecular mechanisms by which PhPIF4 regulates the branching of P. hybrida.