Abstract
To study the molecular mechanism regulating vascular development, we isolated four HD-Zip III homeobox genes that are involved in vascular differentiation in Zinnia. Of them, ZeHB-12 is an IFL1 homologue of Arabidopsis and expressed preferentially in developing xylem. Our analysis of the transcriptional activity and the DNA binding activity of ZeHB-12 revealed that ZeHB-12 is a transcriptional activator bound to the sequence of TAATNATTA. To identify the candidates of ZeHB-12 target genes, we produced Arabidopsis transformants in which ZeHB-12 transcript was overexpressed by dexamethasone treatment. Using the 23K GeneChip microarrays, we picked up genes with a greater than 2.5-fold change after induction of ZeHB-12 expression. They included many genes encoding transcriptional factors and genes involved in xylem parenchyma cell development. These results indicate that ZeHB-12 may regulate the transcriptional cascade leading differentiation of xylem parenchyma cells.
