Elongation and gravitropic responses of Arabidopsis roots are regulated by brassinolide and IAA
Elongation and gravitropic responses of Arabidopsis roots are regulated by brassinolide and IAA
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DOI：
10.1111/j.1365-3040.2007.01659.x
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发表时间：
2007-06-01
影响因子：
7.3
通讯作者：
Kim, Seong-Ki
中科院分区：
文献类型：
--
作者：
Kim, Tae-Wuk;Lee, Sun Min;Kim, Seong-Ki
低浓度（10 ~（-10）M）的外源油菜素（BL）能增加拟南芥初生根的向地性曲率和长度，而高浓度的BL能进一步增加初生根的向地性曲率，同时抑制初生根的生长。BRI 1-GFP植物具有高稳态表达水平的油菜素类固醇（BR）受体激酶，使植物的重力和根生长的反应更敏感，而BR不敏感的突变体，bri 1 -301和bak 1，延迟根的生长，并减少其响应向重力刺激。BL对根向地性曲率的刺激作用在生长素转运突变体aux 1 -7和pin 2中也得到增强，相对于野生型植物，生长素浓度的增加减弱了BL诱导的根对重力的敏感性。有趣的是，IAA处理的bri 1 -301和bak 1植物或植物预处理的BL生物合成抑制剂，油菜素，增加了它们对重力的敏感性，而这些处理的BL-超敏感的转基因植物，BRI 1-GFP和35 S-BAK 1，是不太有效的。CYP 79 B2基因，编码IAA生物合成酶的表达，被抑制在BL-超敏感植物类型和BL-不敏感或缺陷植物增强。总之，我们的研究结果表明，BL与IAA在植物向重力反应和根生长的调节负相互作用，其调节部分是通过调节相应激素的生物合成途径来实现的。
Exogenously applied brassinolide (BL) increased both gravitropic curvature and length of primary roots of Arabidopsis at low concentration (10(-10) M), whereas at higher concentration, BL further increased gravitropic curvature while it inhibited primary root growth. BRI1-GFP plants possessing a high steady-state expression level of a brassinosteroid (BR) receptor kinase rendered the plant's responses to gravity and root growth more sensitive, while BR-insensitive mutants, bri1-301 and bak1, delayed root growth and reduced their response to the gravitropic stimulus. The stimulatory effect of BL on the root gravitropic curvature was also enhanced in auxin transport mutants, aux1-7 and pin2, relative to wild-type plants, and increasing concentration of auxin attenuated BL-induced root sensitivity to gravity. Interestingly, IAA treatment to the roots of bri1-301 and bak1 plants or of plants pretreated with a BL biosynthetic inhibitor, brassinazole, increased their sensitivity to gravity, while these treatments for the BL-hypersensitive transgenic plants, BRI1-GFP and 35S-BAK1, were less effective. Expression of a CYP79B2 gene, encoding an IAA biosynthetic enzyme, was suppressed in BL-hypersensitive plant types and enhanced in BL-insensitive or -deficient plants. In conclusion, our results indicate that BL interacts negatively with IAA in the regulation of plant gravitropic response and root growth, and its regulation is achieved partly by modulating biosynthetic pathways of the counterpart hormone.