Abstract
Previously we found that overexpression of VND7 (Vascular-related NAC Domain Protein 7), which encodes an ORF containing NAC domain, ectopically induces xylem vessel elements in various tissues, clearly indicating that VND7 plays a pivotal role in promoting xylem vessel element differentiation. To understand how VND7 regulates the differentiation, we carried out yeast two-hybrid screening and isolated two distinct cDNAs, VNDIP (VND7-interacting protein) 1 and 2. VNDIP1 and VNDIP2 encode NAC domain proteins previously uncharacterized. VNDIP2 could bind to VND7 with higher affinity than other NAC proteins in vitro. Promoter analysis demonstrated that VNDIP2 is expressed in the specific cell files in root vasculature and immature xylem vessel elements of leaves. Moreover, overexpression of VNDIP2 caused inhibition of protoxylem vessel formation. These data strongly suggests that VNDIP2 also plays important roles in xylem vessel element differentiation.
