Exploring the role of BpPIN3 in hormonal regulation and branching morphogenesis of Betula pendula

This study investigates the role of the BpPIN3 gene in transgenic birch (Betula pendula) and its influence on plant growth and development through hormonal modulation. Previous research suggests that auxin distribution may significantly affect branch development; however, the specific mechanisms underlying this process in birch remain poorly understood. To elucidate these mechanisms, we employed a combination of conventional histological techniques, quantitative analysis of endogenous hormones using UPLC-MS/MS, and detailed RNA sequencing of apex and lateral buds from genetically modified lines (overexpressing BpPIN3, repressing BpPIN3, and wildtype).The results revealed a significant upregulation and downregulation of differentially expressed genes (DEGs) associated with various hormonal pathways, with key functional annotation pointing to stress response, lignin metabolism, and biosynthetic processes. Notably, overexpression of BpPIN3 correlated with decreased auxin levels in lateral buds, while repressing BpPIN3 led to increased auxin in apical buds. This study provides critical insights into how BpPIN3 regulates hormone distribution and affects lateral branching in birch, offering a foundational understanding that can inform further research into hormonal control mechanisms in trees.