MYB transcription factors orchestrating the developmental program of xylem vessels in Arabidopsis roots

Xylem vessel elements play an important role in conducting water and nutrient in land plants. The in vitro culture system, in which subcultured Arabidopsis cells are induced to transdifferentiate into xylem vessel elements, was used to uncover the comprehensive gene expression profile by microarray analysis, which resulted in the identification of many genes encoding transcription factors including two transcriptional key regulators, VASCUAR-RELATED NAC DOMAIN6 (VND6) and VND7. Here we analyze the detailed expression pattern and function of ten genes encoding MYB transcription factors, MYB20, 43, 46, 52, 63, 83, 85, 99, 103, and 118, with the significantly up-regulated expression during the in vitro vessel element differentiation. Of these, six exhibited the specific expression in differentiating xylem vessels in Arabidopsis roots. In addition, MYB46 and MYB83 were shown to upregulate five of these MYB genes, MYB43, 52, 63, 85, and 103. Our results suggest that several MYB genes comprise a transcriptional network during xylem vessel element differentiation in roots.