Plants are sessile in nature and must respond to various environmental cues to regulate their growth orientation. Root hydrotropism, a response to moisture gradients, has been considered to play an important role in drought avoidance. Nonetheless, the processes underlying hydrotropism in roots have remained obscure until recently because of the interfering effect of gravitropism. To shed light on root hydrotropism, we isolated and analyzed two Arabidopsis mutants, mizu-kussei (miz) 1 and 2, that have abnormal hydrotropic responses but normal responses to gravity. MIZ1 encodes a protein of unknown function with a conserved domain at its C-terminus. MIZ2 encodes a guanine-nucleotide exchange factor for ADP-ribosylation factor-type G proteins, which has been identified as GNOM. These findings suggest that roots possess molecular mechanisms essential for hydrotropism but independent of gravitropism. One of such mechanisms involves vesicle transport unique to hydrotropism in roots. Here we summarize recent progress on the molecular mechanism of root hydrotropism and the roles of MIZ1 and MIZ2.
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机译:植物本质上是无柄的,必须对各种环境线索做出反应以调节其生长方向。根系向水性是对水分梯度的响应,被认为在避免干旱方面起着重要作用。尽管如此,由于重力作用的干扰作用,直到最近,根系中趋水性的潜在过程仍然模糊不清。为了阐明根系的亲水性,我们分离并分析了两种拟南芥突变体,mizu-kussei(miz)1和2,它们具有异常的亲水反应,但对重力的反应正常。MIZ1 编码一种功能未知的蛋白质,其 C 末端具有保守结构域。MIZ2 编码 ADP-核糖基化因子 G 型蛋白的鸟嘌呤核苷酸交换因子,该因子已被鉴定为 GNOM。这些发现表明,根系具有对亲水性至关重要的分子机制,但与重力性无关。其中一种机制涉及根系中亲水性特有的囊泡运输。本文综述了近年来根系亲水性的分子机制以及MIZ1和MIZ2的作用研究进展。
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