Abstract
Two types of vessels mature in characteristic positions within protoxylem and metaxylem of the primary xylem tissue. However, the genetic control of differentiation of individual xylem cells is still poorly understood. We carried out the GeneChip analysis during the in vitro vessel element formation system of Arabidopsis and identified many genes encoding transcription factors, whose expression levels were changed significantly during the formation. The functional analysis of these genes was conducted, which included overexpression, RNAi expression, and CRES-T. As a result, we found that overexpression of VASCULAR-RELATED NAC-DOMAIN6 (VND6) and VND7, encoding NAC-domain proteins, can induce transdifferentiation of various cells into metaxylem- and protoxylem-like vessel elements, respectively, in Arabidopsis roots and poplar leaves and that CRES-T of VND6 and VND7 specifically inhibits metaxylem and protoxylem vessel formation in Arabidopsis roots, respectively. Recent results on the functional analysis of other transcription factor-encoding genes will be also discussed.
