Unique ethylene-regulated touch responses of Arabidopsis thaliana roots to physical hardness
Unique ethylene-regulated touch responses of Arabidopsis thaliana roots to physical hardness
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DOI：
10.1007/s10265-008-0178-4
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发表时间：
2008-09-01
影响因子：
2.8
通讯作者：
Tanaka, Shigeo
中科院分区：
文献类型：
--
作者：
Yamamoto, Chigusa;Sakata, Yoichi;Tanaka, Shigeo
尽管植物根部的触摸反应是一种重要的适应性行为，但其分子机制仍不清楚。我们开发了一种生物测定法，用于测量拟南芥幼苗根部弯曲对物理硬度的反应。我们的测试需要两层固体培养基。初生根穿过上层0.3%植胶向下生长，或者穿透下层，或者沿着不同浓度（0.2-0.5%，对应硬度1.57-6.79 gw mm(-2)）上下层之间的界面弯曲。我们发现，随着下层硬度的增加，根部弯曲的百分比增加，乙烯产量减少，这表明根部弯曲响应与乙烯产量之间存在反比关系。对乙烯生物合成调节剂和突变体的研究还表明，根部对中等硬度的弯曲和非弯曲反应分别取决于乙烯生物合成的减少和增加。此外，根尖软化程度和根细胞生长差异（决定根弯曲反应的两个可能因素）分别因乙烯量的减少和增加而增强和减弱——在弯曲根和非弯曲根中也是如此。我们的研究结果表明，乙烯可能通过根尖软化（或硬化）和差异根细胞生长的结合来调节根部触摸反应。
Although touch responses of plant roots are an important adaptive behavior, the molecular mechanism remains unclear. We have developed a bioassay for measuring root-bending responses to physical hardness in Arabidopsis thaliana seedlings. Our test requires a two-layer solid medium. Primary roots growing downward through an upper layer of 0.3% phytagel either penetrate the lower layer or bend along an interface between the upper and lower layers with different concentrations (0.2-0.5%, corresponding to 1.57-6.79 gw mm(-2) in hardness). In proportion to increasing hardness of the lower layer, we found that the percentage of bending roots increased and ethylene production decreased, suggesting an inverse relationship between the root-bending response and ethylene production. Studies with ethylene biosynthesis modulators and mutants also suggested that bending and non-bending responses of roots to medium hardness depend, respectively, on decreased and increased ethylene biosynthesis. In addition, the degrees of root-tip softening and differential root-cell growth, both possible factors determining root-bending response, were enhanced and attenuated by decreased and increased amounts of ethylene, respectively-also in bending roots and non-bending roots. Our findings indicate that ethylene regulates root touch responses, probably through a combination of root-tip softening (or hardening) and differential root-cell growth.