Isolation and characterization of a rice WUSCHEL-type homeobox gene that is specifically expressed in the central cells of a quiescent center in the root apical meristem.
The Arabidopsis WUSCHEL (WUS) protein, which plays an important role in the specification of the stem cells in the shoot apical meristem (SAM), contains an 'atypical' homeodomain (HD) with extra residues in its loop and turn regions. We speculated that a WUS-type atypical HD protein might also be involved in the specification and maintenance of the root apical meristem (RAM) stem cells of rice. To investigate this possibility, we isolated and characterized a rice WUS-type homeobox gene designated quiescent-center-specific homeobox (QHB) gene. Using transformants carrying the QHB promoter-GUS and in situ hybridization, we found that QHB was specifically expressed in the central cells of a quiescent center (QC) of the root. During embryogenesis and crown root formation, QHB expression was observed prior to the morphological differentiation of the root. However, we detected different QHB expression patterns in the process of the RAM development, specifically between radicle and crown root formation, suggesting that the cell-fate determination of the QC may be controlled by different mechanisms. We also produced transformants that overexpress QHB or Arabidopsis WUS. These transformants did not form crown roots, but developed multiple shoots from ectopic SAMs with malformed leaves. On the basis of these observations, we propose that the WUS-type homeobox gene is involved in the specification and maintenance of the stem cells (QC cells) in the RAM, by a mechanism similar to that for WUS in the SAM.
Kamiya
Noriko
N
Nagoya University, BioScience Center, Chikusa, Nagoya 464-8601, Japan.
Nagasaki
Hiroshi
H
Morikami
Atsushi
A
Sato
Yutaka
Y
Matsuoka
Makoto
M
D000595:Amino Acid Sequence; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics; D001483:Base Sequence; D018744:DNA, Plant; D015870:Gene Expression; D005801:Genes, Homeobox; D017343:Genes, Plant; D018398:Homeodomain Proteins / Q000737:chemistry / Q000235:genetics; D018519:Meristem; D008969:Molecular Sequence Data; D012275:Oryza / Q000196:embryology / Q000235:genetics* / Q000254:growth & development; D010940:Plant Proteins / Q000235:genetics; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism*; D030821:Plants, Genetically Modified
D029681:Arabidopsis Proteins; D018744:DNA, Plant; D018398:Homeodomain Proteins; D010940:Plant Proteins; C116421:WUSCHEL protein, Arabidopsis