Abstract
To investigate the molecular mechanism of vascular differentiation, we newly isolated a HD-Zip III homeobox gene from Zinnia (ZeHB-13) and compared the accumulation pattern of the ZeHB-13 transcript with those for other three HD-Zip III genes that had been already examined (ZeHB-10,-11,-12). In a Zinnia cell culture, although transcript for ZeHB-13 was accumulated in a xylogenesis-specific manner similar to the ZeHB-10,-11,-12 transcripts, the ZeHB-13 transcript was detected earlier than the ZeHB-10,-11,-12 transcripts during xylem differentiation. The accumulation of the ZeHB-10,-11,-12 transcripts was up-regulated by brassinosteroid, but that of ZeHB-13 was not. In situ hybridization analysis showed that the ZeHB-13 transcript was restricted to vascular regions, especially to procambium. These results suggest that ZeHB-13 regulates earlier step of xylem differentiation than ZeHB-10,-11,-12.
