title: Class III homeodomain leucine-zipper proteins regulate xylem cell differentiation.
abstract: Although it has been suggested that class III homeodomain leucine-zipper proteins (HD-Zip III) are involved in vascular development, details of the function of individual HD-Zip III proteins in vascular differentiation have not been resolved. To understand the function of each HD-Zip III protein in vascular differentiation precisely, we analyzed the in vitro transcriptional activity and in vivo function of Zinnia HD-Zip III genes, ZeHB-10, ZeHB-11 and ZeHB-12, which show xylem-related expression. Transgenic Arabidopsis plants harboring cauliflower mosaic virus 35S-driven ZeHB-10 and ZeHB-12 with a mutation in the START domain (mtZeHB-10, mtZeHB-12) showed a higher production of tracheary elements (TEs) and xylem precursor cells, respectively. A systematic analysis with Genechip arrays revealed that overexpression of mtZeHB-12 rapidly induced various genes, including brassinosteroid-signaling pathway-related genes and genes for transcription factors that are expressed specifically in vascular tissues in situ. Furthermore, mtZeHB-12 overexpression did not induce TE-specific genes, including genes related to programmed cell death and lignin polymerization, but did induce lignin monomer synthesis-related genes, which are expressed in xylem parenchyma cells. These results suggest that ZeHB-12 is involved in the differentiation of xylem parenchyma cells, but not of TEs.
authors.affiliation: Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Japan. koito@stanford.edu
authors.forename: Kyoko
authors.initials: K
authors.lastname: Ohashi-Ito
authors.forename: Minoru
authors.initials: M
authors.lastname: Kubo
authors.forename: Taku
authors.initials: T
authors.lastname: Demura
authors.forename: Hiroo
authors.initials: H
authors.lastname: Fukuda
mesh_terms: D019659:Asteraceae / Q000166:cytology* / Q000235:genetics; D001483:Base Sequence; D002454:Cell Differentiation; D017931:DNA Primers; D017343:Genes, Plant; D018398:Homeodomain Proteins / Q000235:genetics / Q000502:physiology*; D016350:Leucine Zippers; D016297:Mutagenesis, Site-Directed; D020411:Oligonucleotide Array Sequence Analysis; D030821:Plants, Genetically Modified / Q000166:cytology / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: D017931:DNA Primers; D018398:Homeodomain Proteins