Transcriptome Analysis Reveals the Mechanism of Early Branching of Balsa (Ochroma lagopus Swartz)

Balsa (Ochroma lagopus Swartz), the world's lightest wood and a crucial material in wind turbine blades, holds significant potential to contribute to carbon neutrality efforts when cultivated in tropical areas such as Xishuangbanna, China. However, balsa trees planted in Xishuangbanna exhibit early branching, resulting in reduced wood yield. Our study investigated the pivotal factors in regulating shoot apical dominance and branching by comparing an early-branching cultivar from Indonesia with a late-branching cultivar from Ecuador. Through transcriptome analysis, we found that the decreased expression of genes putatively involved in shoot apical meristem (SAM) activity, including putative orthologs of WUSCHEL (OlWUS-like), SHOOTMERISTEMLESS (OlSTM-like), and CLAVATA3 (OlCLV3-like), was associated with shoot apical dominance and lateral meristem development in early-branch cultivars. Additionally, the increased expression of flowering-related genes, including putative orthologs of FLOWERING LOCUS T (OlFT-like), LEAFY (OlLFY-like), and MADS-box genes, was implicated in flowering meristem formation and branch initiation. Notably, we identified a highly expressed OlFT-like gene that may participate in flowering and branching. Overexpression of OlFT-like in Jatropha curcas inhibited the longitudinal growth of the main stem, promoted branching, and intrinsically decreased the expression of genes involved in the control of meristematic activity (JcWUSa, JcWUSb, and JcCLV3). In summary, OlFT-like was identified as a key regulator of flowering and branching in balsa. Our in-depth understanding of the branching of perennials provides novel insights for the early screening of elite ecotypes and molecular breeding of balsa.