A gene essential for hydrotropism in roots
A gene essential for hydrotropism in roots
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DOI：
10.1073/pnas.0609929104
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发表时间：
2007-03-13
影响因子：
11.1
通讯作者：
Takahashi, Hideyuki
中科院分区：
文献类型：
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作者：
Kobayashi, Akie;Takahashi, Akiko;Takahashi, Hideyuki
根表现出对水分梯度的亲水性，这被认为是控制其生长方向、获得水分和在陆地环境中站稳脚跟的重要因素。然而，亲水性的分子机制仍不清楚。在这里，我们报道了拟南芥突变体mizu-kussei1(Miz1)的根，它们的向水性受损，表现出正常的向重力性和伸长生长。Miz1植株的根部向光性减弱，对波浪形的生长反应有所改善。Miz1与野生型植株在形态特征和根系结构上没有明显差异。这些结果表明，诱导亲水性的途径不依赖于用于其他亲水性反应的途径。这种表型是由MIZ1中的一个隐性突变引起的，该突变编码一种含有在水稻和苔藓等陆生植物中高度保守的结构域的蛋白质。在已知的生物基因组中，如绿藻、红藻、蓝藻或动物中没有发现MiZ结构域。我们推测，MIZ1已经进化为在适应陆地生命方面发挥重要作用，因为亲水作用可能有助于高等植物避免干旱。此外，pMIZ1：：GUS融合基因在根冠小柱细胞中强烈表达，但在伸长区不表达，表明MIZ1在亲水反应的早期阶段发挥作用。
Roots display hydrotropism in response to moisture gradients, which is thought to be important for controlling their growth orientation, obtaining water, and establishing their stand in the terrestrial environment. However, the molecular mechanism underlying hydrotropism remains unknown. Here, we report that roots of the Arabidopsis mutant mizu-kussei1 (miz1), which are impaired in hydrotropism, show normal gravitropism and elongation growth. The roots of miz1 plants showed reduced phototropism and a modified wavy growth response. There were no distinct differences in morphological features and root structure between miz1 and wild-type plants. These results suggest that the pathway inducing hydrotropism is independent of the pathways used in other tropic responses. The phenotype results from a single recessive mutation in MIZ1, which encodes a protein containing a domain (the MIZ domain) that is highly conserved among terrestrial plants such as rice and moss. The MIZ domain was not found in known genomes of organisms such as green algae, red algae, cyanobacteria, or animals. We hypothesize that MIZ1 has evolved to play an important role in adaptation to terrestrial life because hydrotropism could contribute to drought avoidance in higher plants. In addition, a pMIZ1::GUS fusion gene was expressed strongly in columella cells of the root cap but not in the elongation zone, suggesting that MIZ1 functions in the early phase of the hydrotropic response.