The HALTED ROOT gene encoding the 26S proteasome subunit RPT2a is essential for the maintenance of Arabidopsis meristems
The HALTED ROOT gene encoding the 26S proteasome subunit RPT2a is essential for the maintenance of Arabidopsis meristems
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DOI：
10.1242/dev.01096
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发表时间：
2004-05
期刊：
影响因子：
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通讯作者：
Minako Ueda;K. Matsui;S. Ishiguro;R. Sano;T. Wada;I. Paponov;K. Palme;K. Okada
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文献类型：
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作者：
Minako Ueda;K. Matsui;S. Ishiguro;R. Sano;T. Wada;I. Paponov;K. Palme;K. Okada
在高等植物中，胚后发育依赖于根和茎顶端分生组织（RAM和SAM）的活性。RAM中的静止中心（QC）和SAM中的组织中心（OC）被认为是维持分生组织活动所必需的。为了了解维持胚后分生组织的机制，我们分离了拟南芥突变体，停止根（hlr）。在该突变体中，根和茎中胚后分生组织的细胞组织被破坏，并且它们的分生组织活性降低或变得异常。我们发现，突变RAM发芽后失去了QC身份，这是指定在胚胎发生过程中，而分化组织的身份保持。在胚后SAM中，一个典型的OC标记基因WUSCHEL的表达模式在突变体中受到干扰。这些观察结果表明，β-SMA基因是维持RAM和SAM的细胞组织和正常性质所必需的。RPT 2a是26 S蛋白酶体的一个亚基，在不同的细胞过程中降解关键蛋白。我们发现，在RAM和SAM中，包括在QC和OC，分别表达的cDNA 3基因，并在突变体中的蛋白酶体的活性降低。我们建议，蛋白酶体依赖的程序化蛋白水解是必需的，以保持分生组织的完整性，无论是在地上部和根。
In higher plants, post-embryonic development is dependent on the activity of the root and shoot apical meristem (RAM and SAM). The quiescent center (QC) in the RAM and the organizing center (OC) in the SAM are known to be essential for the maintenance of meristematic activity. To understand the mechanism that maintains post-embryonic meristems, we isolated an Arabidopsis mutant, halted root (hlr). In this mutant, the cellular organization was disrupted in post-embryonic meristems both in the root and in the shoot, and their meristematic activity was reduced or became abnormal. We showed that the mutant RAM lost its QC identity after germination, which was specified during embryogenesis, whereas the identity of differentiated tissues was maintained. In the post-embryonic SAM, the expression pattern of a typical OC marker gene, WUSCHEL, was disturbed in the mutant. These observations indicate that the HLR gene is essential to maintain the cellular organization and normal nature of the RAM and SAM. The HLR gene encodes RPT2a, which is a subunit of the 26S proteasome that degrades key proteins in diverse cellular processes. We showed that the HLR gene was expressed both in the RAM and in the SAM, including in the QC and the OC, respectively, and that the activity of proteasomes were reduced in the mutant. We propose that proteasome-dependent programmed proteolysis is required to maintain the meristem integrity both in the shoot and in the root.