ClIAA27编码一种Aux/IAA蛋白质，是转基因烟草中侧芽发育和枝条生长的重要调控因子。

Abstract

12 ClIAAs were identified in Chinese fir. • The ClIAA27 acts as a hub in the co-expression network. • ClIAAs’ expression pattern exhibits dynamic variations. • ClIAA27 positively regulates lateral bud development and shoot branching. Cunninghamia lanceolata (Chinese fir) is a fast-growing industrial timber species of paramount importance in southern China, extensively cultivated due to its high productivity and superior wood quality. Branching, as one of the most critical morphological traits in plants, directly influences both timber yield and quality. As a plant growth regulator, auxin plays a fundamental regulatory role in lateral bud outgrowth and shoot branching development. However, the molecular mechanisms underlying auxin-mediated lateral bud formation remain poorly characterized in conifers, particularly in Chinese fir, and the functional roles of Aux/IAA family in auxin signaling remain largely unexplored. For this reason, a systematic genome-wide identification of the Aux/IAA family in Chinese fir was performed. Our analysis identified 12 ClIAA genes distributed across six chromosomes, exhibiting three distinct expression patterns during different developmental stages. Tissue-specific expression profiling and auxin responsiveness assays of selected ClIAAs suggested that ClIAA27 may serve as a key regulator of lateral bud development. Functional studies demonstrated that ClIAA27 -overexpressing (OE) transgenic lines exhibited enhanced lateral bud formation, reduced plant height, thinner stems, and altered sugar allocation in axillary meristems compared to wild-type (WT) controls. Furthermore, the specific expression of ClIAA27 in tobacco significantly modulated the transcript levels of genes involved in hormone signaling and branching regulation. Collectively, these discoveries establish the critical involvement of ClIAA27 in lateral bud formation and branch growth, providing a foundation for extended investigation into the regulatory mec