Microtubule-associated protein 70 links brassinosteroid signaling to fruit morphogenesis in tomato

Microtubule-associated proteins (MAPs) are essential regulators of cell division and expansion, yet how they integrate hormonal signals to control fruit morphogenesis remains elusive. Here, we show that tomato SlMAP70-1 and SlMAP70-2 act as key downstream effectors of brassinosteroid (BR) signaling during fruit development. Exogenous eBL treatment analyses reveal that SlMAP70s are required for BR-induced hypocotyl and fruit elongation, with loss of SlMAP70s function leading to reduced BR sensitivity. We further establish that SlMAP70s are directly activated by the transcription factors SlBZR1.2 and SlBZR1.5. Transcriptomic data showed that SlMAP70s deficiency leads to significant downregulation of genes involved in cell wall organization and auxin transport. Thus, BR signaling shapes fruit morphology by modulating SlMAP70s expression and downstream cellular processes. Together, these results establish a molecular framework by which BR signaling orchestrates the microtubule cytoskeleton to shape plant organs.