Abstract
The Arabidopsis thaliana NAC domain transcription factor, VASCULAR-RELATED NAC-DOMAIN7 (VND7), acts as a master regulator of the differentiation of xylem vessels. To understand the mechanism by which VND7 regulates xylem vessel differentiation, we screened for proteins that interact with VND7 with a yeast two-hybrid system, and identified a cDNA encoding a NAC domain protein, VND-INTERACTING2 (VNI2). The expression of VNI2 overlaps with that of VND7 in elongating vessel precursors in roots, whereas the initiation and termination of VNI2 expression always precedes those of VND7 expression. Transient reporter assays showed that VNI2 is a transcriptional repressor and can repress the expression of vessel-specific genes regulated by VND7. The expression of the VNI2 under the control of the VND7 promoter resulted in the inhibition of the normal development of xylem vessels. These data suggest that VNI2 regulates xylem cell specification as a transcriptional repressor that interacts with VND7.
