The temporally regulated morphogenesis of plant organs depends critically on the precise differentiation of meristem stem cells. This process is propelled by the orchestrated dynamics of specific stem cell populations within both the apical and lateral meristems, which drive longitudinal elongation and radial thickening. Although considerable progress has been made in elucidating longitudinal growth mediated by apical meristems, the spatiotemporal mechanisms governing radial growth via the vascular cambium remain incompletely characterized. Here, we generated high-resolution single-cell transcriptomes of stem tissues from the cotton cultivar ZM24. Gene regulatory network analysis identified GhXTHB as highly expressed in the vascular cambium region. Overexpression of GhXTHB reduced the number of vascular cambium layers and xylem width compared to WT, whereas CRISPR/Cas9-mediated knockout of GhXTHB increased cambium cell layers without affecting xylem width. Upstream of GhXTHB, we identified GhTALE, whose overexpression promoted cambium cell proliferation and increased the number of cambial layers. In contrast, GhTALE knockout (KO-GhTALE) reduced both cambial proliferation and xylem width. Notably, GhXTHB expression was upregulated in GhTALE-edited lines, indicating that GhTALE acts as a negative regulator of GhXTHB. Further analysis revealed that GhTALE physically interacts with GhOFP1, and GhOFP1 knockout increased the number of vascular cambium cell layers. Mechanistically, GhOFP1 is recruited to the GhXTHB promoter via interaction with GhTALE, modulating vascular cambium development. These findings establish the GhOFP1-GhTALE-GhXTHB module as a potential regulatory factors of vascular cambium proliferation in cotton stems, offering new insight into transcriptional control of stem architecture and biomass accumulation.
Xu et al. (Fri,) studied this question.