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
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
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DOI：
10.1046/j.1365-313x.2003.01816.x
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发表时间：
2003-08-01
期刊：
影响因子：
7.2
通讯作者：
Matsuoka, M
中科院分区：
文献类型：
--
作者：
Kamiya, N;Nagasaki, H;Matsuoka, M
拟南芥WUSCHEL（WUS）蛋白在茎顶端分生组织（SAM）干细胞的特化过程中起着重要作用，它含有一个在其环和转角区域具有额外残基的“非典型”同源结构域（HD）。我们推测，WUS型非典型HD蛋白也可能参与水稻根尖分生组织（RAM）干细胞的特化和维持。为了研究这种可能性，我们分离并鉴定了水稻WUS型同源盒基因，命名为静止中心特异性同源盒（QHB）基因。利用携带QHB启动子-GUS的转化子和原位杂交，我们发现QHB特异表达于根的静止中心（QC）的中央细胞。在胚胎发生和冠状根形成过程中，观察到QHB表达之前的形态分化的根。然而，我们检测到不同的QHB表达模式的RAM发展的过程中，特别是胚根和冠根形成之间，这表明QC的细胞命运的决定可能是由不同的机制控制。我们还产生过表达QHB或拟南芥WUS的转化体。这些转化体没有形成冠状根，但从具有畸形叶的异位SAM发育出多个芽。基于这些观察结果，我们提出WUS型同源框基因参与RAM中干细胞（QC细胞）的特化和维持，其机制类似于SAM中的WUS。
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.