MirMAN-mediated mannose promotes root development in <i>Arabidopsis</i> via the MYB41-DWF4 module regulating brassinosteroid signaling pathways

Sugars serve both as nutritional sources and signaling entities in plant root systems, engaging in crosstalk with phytohormones to modulate root morphogenesis and growth. Previous investigations demonstrated that heterologous expression of the Mirabilis jalapa mannanase gene (MirMAN) in Arabidopsis thaliana significantly promotes root development. Nevertheless, the mechanistic basis and associated signaling networks underpinning this phenomenon remain poorly elucidated. In this study, we found that MirMAN-mediated mannose could significantly promote plant root development, participate in root morphogenesis by promoting lateral root emergence and root elongation. Moreover, MirMAN-mediated mannose could increase the content of endogenous auxin, elevated the expression of auxin transport genes (AtLAX3/AtPIN2) and the response factor (AtARF7/19), lateral root development-related genes (AtLBD16/29), cell cycle-related gene (AtGATA23), sugar signaling-related genes (AtSnRK1) to promote lateral root development. Furthermore, the expression of AtMYB41 was significantly increased by MirMAN-mediated mannose. We further found that MYB41 directly bound to the promoter of AtDWF4 (a BR biosynthetic gene) and positively regulate the transcription of AtDWF4. Consistent with these findings, the myb41 mutants exhibited fewer lateral roots, reduced AtDWF4 expression, and lower BR content. Collectively, These results provide new perspectives for understanding the mechanisms of endogenous plant sugar signaling, and provide new ideas for exploiting the plastic developmental capacity of plant roots.