MOLECULAR MECHANISMS OF HYDROTROPISM IN SEEDLING ROOTS OF ARABIDOPSIS THALIANA (BRASSICACEAE)
MOLECULAR MECHANISMS OF HYDROTROPISM IN SEEDLING ROOTS OF ARABIDOPSIS THALIANA (BRASSICACEAE)
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DOI：
10.3732/ajb.1200419
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发表时间：
2013-01-01
影响因子：
3
通讯作者：
Takahashi, Hideyuki
中科院分区：
文献类型：
--
作者：
Moriwaki, Teppei;Miyazawa, Yutaka;Takahashi, Hideyuki
根对水分梯度表现出正的亲水性，这被认为有助于植物获得水分。本文综述了拟南芥幼苗根部亲水性的生理和分子遗传学研究进展。我们发现Mizu-KUSSEI1(MIZ1)和MIZ2是根的亲水性必需基因，前者编码一种未知功能的蛋白质，后者编码一种参与囊泡运输的ARF-Global(GNOM)蛋白。由于这两个突变体在亲水性方面都有缺陷，但在向重力性方面没有缺陷，这些突变可能会影响亲水性独有的分子机制。MIZ1在侧根帽和根本身的皮层中表达。它定位于细胞质中的一种可溶性蛋白，与根细胞的内质网膜的细胞质表面有关。光和ABA独立地调节MIZ1的表达，从而影响最终的亲水性反应。此外，过表达MIZ1还会增强侧根的亲水性，抑制侧根的形成。这种表型可能与根中生长素含量的变化有关。具体地说，在MIZ1过表达的突变体中，根中的生长素水平降低，而在MIZ1突变体中增加。与大多数gnom突变体不同，miz2表现出正常的形态、生长和向重力性，具有正常的PIN蛋白定位。MIZ1可能通过调节拟南芥根中生长素的内源水平，在拟南芥的亲水反应中发挥重要作用。此外，GNOM/MIZ2在亲水性中的作用与向重力性中的作用不同。
Roots show positive hydrotropism in response to moisture gradients, which is believed to contribute to plant water acquisition. This article reviews the recent advances of the physiological and molecular genetic studies on hydrotropism in seedling roots of Arabidopsis thaliana. We identified MIZU-KUSSEI1 (MIZ1) and MIZ2, essential genes for hydrotropism in roots; the former encodes a protein of unknown function, and the latter encodes an ARF-GEF (GNOM) protein involved in vesicle trafficking. Because both mutants are defective in hydrotropism but not in gravitropism, these mutations might affect a molecular mechanism unique to hydrotropism. MIZ1 is expressed in the lateral root cap and cortex of the root proper. It is localized as a soluble protein in the cytoplasm and in association with the cytoplasmic face of endoplasmic reticulum (ER) membranes in root cells. Light and ABA independently regulate MIZ1 expression, which influences the ultimate hydrotropic response. In addition, MIZ1 overexpression results in an enhancement of hydrotropism and an inhibition of lateral root formation. This phenotype is likely related to the alteration of auxin content in roots. Specifically, the auxin level in the roots decreases in the MIZ1 overexpressor and increases in the miz1 mutant. Unlike most gnom mutants, miz2 displays normal morphology, growth, and gravitropism, with normal localization of PIN proteins. It is probable that MIZ1 plays a crucial role in hydrotropic response by regulating the endogenous level of auxin in Arabidopsis roots. Furthermore, the role of GNOM/MIZ2 in hydrotropism is distinct from that of gravitropism.