NcBRI1 positively regulate vascular development and promote biomass production in Neolamarckia cadamba.

Brassinosteroids (BRs) are essential phytohormones that play a crucial role in plant growth and development. However, our understanding of BR receptors and their functions in tree species is currently limited. In this study, we looked for potential BR receptor genes in the burflower-tree (Neolamarckia cadamba) genome. We identified five candidate gene from sequence analysis and phylogenetic reconstruction. Among these genes, Neolamarckia cadamba BRASSINOSTEROID-INSENSITIVE 1 (NcBRI1) is ubiquitously expressed in all tested tissues and encodes a functional BR receptor localized to the plasma membrane. Ectopic expression of NcBRI1 in the Arabidopsis (Arabidopsis thaliana) loss-of-function BRI1 mutant bri1-5 not only rescued its growth retardation phenotype but also facilitated vascular development by reactivating BR signal transduction. Furthermore, overexpression of NcBRI1 promoted vascular formation and cell elongation in transgenic hairy roots of Neolamarckia cadamba. By contrast, microRNA-mediated knockdown of NcBRI1 resulted in delayed vascular development and smaller cells. Importantly, we found that manipulation of NcBRI1 in Neolamarckia cadamba can enhance the biomass of hairy roots. These findings highlight the critical role of NcBRI1 in BR signaling and its significant influence on vascular development and rapid growth in Neolamarckia cadamba.