title: A novel Arabidopsis gene TONSOKU is required for proper cell arrangement in root and shoot apical meristems.
abstract: Root apical meristem (RAM) and shoot apical meristem (SAM) are vital for the correct development of the plant. The direction, frequency, and timing of cell division must be tightly controlled in meristems. Here, we isolated new Arabidopsis mutants with shorter roots and fasciated stems. In the tonsoku (tsk) mutant, disorganized RAM and SAM formation resulted from the frequent loss of proper alignment of the cell division plane. Irregular cell division also occurred in the tsk embryo, and the size of cells in meristems and embryo in tsk mutant was larger than in the wild type. In the enlarged SAM of the tsk mutant, multiple centers of cells expressing WUSCHEL (WUS) were observed. In addition, expression of SCARECROW (SCR) in the quiescent center (QC) disappeared in the disorganized RAM of tsk mutant. These results suggest that disorganized cell arrangements in the tsk mutants result in disturbed positional information required for the determination of cell identity. The TSK gene was found to encode a protein with 1311 amino acids that possesses two types of protein-protein interaction motif, leucine-glycine-asparagine (LGN) repeats and leucine-rich repeats (LRRs). LGN repeats are present in animal proteins involved in asymmetric cell division, suggesting the possible involvement of TSK in cytokinesis. On the other hand, the localization of the TSK-GFP (green fluorescent protein) fusion protein in nuclei of tobacco BY-2 cells and phenotypic similarity of tsk mutants to other fasciated mutants suggest that the tsk mutation may cause disorganized cell arrangements through defects in genome maintenance.
authors.affiliation: Laboratory of Biochemistry, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa, Nagoya 464-8601, Japan. i992009d@mbox.nagoya-u.ac.jp
authors.forename: Takamasa
authors.initials: T
authors.lastname: Suzuki
authors.forename: Soichi
authors.initials: S
authors.lastname: Inagaki
authors.forename: Sakiko
authors.initials: S
authors.lastname: Nakajima
authors.forename: Takafumi
authors.initials: T
authors.lastname: Akashi
authors.forename: Masa-Aki
authors.initials: MA
authors.lastname: Ohto
authors.forename: Masatomo
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Motoaki
authors.initials: M
authors.lastname: Seki
authors.forename: Kazuo
authors.initials: K
authors.lastname: Shinozaki
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Kato
authors.forename: Satoshi
authors.initials: S
authors.lastname: Tabata
authors.forename: Kenzo
authors.initials: K
authors.lastname: Nakamura
authors.forename: Atsushi
authors.initials: A
authors.lastname: Morikami
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics; D001483:Base Sequence; D002455:Cell Division; D017931:DNA Primers; D018506:Gene Expression Regulation, Plant / Q000235:genetics*; D017403:In Situ Hybridization; D018519:Meristem / Q000166:cytology*; D008969:Molecular Sequence Data; D018517:Plant Roots / Q000166:cytology*; D011505:Protein-Tyrosine Kinases / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D029681:Arabidopsis Proteins; D017931:DNA Primers; D011505:Protein-Tyrosine Kinases; C080813:emt protein-tyrosine kinase