Auxin-induced inhibition of lateral root initiation contributes to root system shaping in Arabidopsis thaliana
Auxin-induced inhibition of lateral root initiation contributes to root system shaping in Arabidopsis thaliana
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DOI：
10.1111/j.1365-313x.2010.04365.x
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发表时间：
2010-12-01
期刊：
影响因子：
7.2
通讯作者：
Dubrovsky, Joseph G.
中科院分区：
文献类型：
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作者：
Ivanchenko, Maria G.;Napsucialy-Mendivil, Selene;Dubrovsky, Joseph G.
已知生长素抑制根的伸长并促进侧根的形成。在这里，我们报道了生长素对根侧根形成的复杂影响，在生长素处理后，根的细胞伸长减少。在纳摩尔范围内，吲哚-3-乙酸（IAA）对拟南芥侧根形成的促进作用随着IAA浓度的增加而减弱，在25 nm处IAA具有抑制作用。检测这种意想不到的抑制作用需要评估在处理期间新形成的根部分，与处理前存在的根部分分开。内源IAA水平升高的iam - ox拟南芥品系侧根形成也减少。乙烯信号突变体ein2-5和etr1-3，生长素运输突变体aux1-7和eir1/pin2，以及生长素感知/响应突变体tir1-1均能抵抗IAA对侧根形成的抑制作用，这与乙烯信号、生长素运输和生长素感知/响应的完整要求相一致。中柱鞘细胞长度的减少幅度小于皮层细胞长度的减少幅度，表明随着IAA水平的增加，中柱鞘细胞数量相对于皮层的减少可能会发生。DR5:GUS生长素报告基因的表达也不太有效，AXR3生长素抑制蛋白在这些根部分也不太有效地消除，这表明生长素反应性降低可能伴随着抑制。我们的研究强调了生长素调控的抑制亲本根伸长和侧根起始减少之间的联系。这可能需要调节侧根间距和优化根结构以适应环境要求。
P>The hormone auxin is known to inhibit root elongation and to promote initiation of lateral roots. Here we report complex effects of auxin on lateral root initiation in roots showing reduced cell elongation after auxin treatment. In Arabidopsis thaliana, the promotion of lateral root initiation by indole-3-acetic acid (IAA) was reduced as the IAA concentration was increased in the nanomolar range, and IAA became inhibitory at 25 nm. Detection of this unexpected inhibitory effect required evaluation of root portions that had newly formed during treatment, separately from root portions that existed prior to treatment. Lateral root initiation was also reduced in the iaaM-OX Arabidopsis line, which has an endogenously increased IAA level. The ethylene signaling mutants ein2-5 and etr1-3, the auxin transport mutants aux1-7 and eir1/pin2, and the auxin perception/response mutant tir1-1 were resistant to the inhibitory effect of IAA on lateral root initiation, consistent with a requirement for intact ethylene signaling, auxin transport and auxin perception/response for this effect. The pericycle cell length was less dramatically reduced than cortical cell length, suggesting that a reduction in the pericycle cell number relative to the cortex could occur with the increase of the IAA level. Expression of the DR5:GUS auxin reporter was also less effectively induced, and the AXR3 auxin repressor protein was less effectively eliminated in such root portions, suggesting that decreased auxin responsiveness may accompany the inhibition. Our study highlights a connection between auxin-regulated inhibition of parent root elongation and a decrease in lateral root initiation. This may be required to regulate the spacing of lateral roots and optimize root architecture to environmental demands.