This study identifies VND6 and VND7 as transcription factors that regulate the formation of protoxylem and metaxylem vessel elements in plants. Using an in vitro system for xylem vessel element formation in Arabidopsis, the researchers found that VND6 and VND7 can induce transdifferentiation of various cells into metaxylem- and protoxylem-like vessel elements, respectively. These genes are expressed in specific regions of the root and shoot, with VND6 primarily in the central metaxylem vessels and VND7 in the immature protoxylem vessels. Overexpression of VND6 and VND7 in transgenic plants resulted in the formation of metaxylem and protoxylem-like vessel elements in various cell types, suggesting their role as transcription switches for xylem vessel formation. Conversely, dominant repression of VND6 and VND7 inhibited metaxylem and protoxylem vessel formation, respectively. The study also shows that VND6 and VND7 function downstream of phytohormone signaling pathways, including auxin, cytokinin, and brassinosteroids. These findings suggest that VND6 and VND7 are master regulators of xylem vessel cell fate, controlling the expression of target genes involved in cell differentiation. The study further indicates that the hierarchical genetic control of xylem vessel formation is conserved across plant species, as overexpression of VND6 and VND7 in poplar resulted in similar transdifferentiation of mesophyll and epidermal cells into metaxylem- and protoxylem-like vessel elements. This research provides insights into the molecular mechanisms underlying xylem vessel formation and highlights the importance of transcription factors in plant vascular development.This study identifies VND6 and VND7 as transcription factors that regulate the formation of protoxylem and metaxylem vessel elements in plants. Using an in vitro system for xylem vessel element formation in Arabidopsis, the researchers found that VND6 and VND7 can induce transdifferentiation of various cells into metaxylem- and protoxylem-like vessel elements, respectively. These genes are expressed in specific regions of the root and shoot, with VND6 primarily in the central metaxylem vessels and VND7 in the immature protoxylem vessels. Overexpression of VND6 and VND7 in transgenic plants resulted in the formation of metaxylem and protoxylem-like vessel elements in various cell types, suggesting their role as transcription switches for xylem vessel formation. Conversely, dominant repression of VND6 and VND7 inhibited metaxylem and protoxylem vessel formation, respectively. The study also shows that VND6 and VND7 function downstream of phytohormone signaling pathways, including auxin, cytokinin, and brassinosteroids. These findings suggest that VND6 and VND7 are master regulators of xylem vessel cell fate, controlling the expression of target genes involved in cell differentiation. The study further indicates that the hierarchical genetic control of xylem vessel formation is conserved across plant species, as overexpression of VND6 and VND7 in poplar resulted in similar transdifferentiation of mesophyll and epidermal cells into metaxylem- and protoxylem-like vessel elements. This research provides insights into the molecular mechanisms underlying xylem vessel formation and highlights the importance of transcription factors in plant vascular development.