Evidence that L-glutamate can act as an exogenous signal to modulate root growth and branching in Arabidopsis thaliana
Evidence that L-glutamate can act as an exogenous signal to modulate root growth and branching in Arabidopsis thaliana
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DOI：
10.1093/pcp/pcj075
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发表时间：
2006-08-01
影响因子：
4.9
通讯作者：
Forde, Brian G.
中科院分区：
文献类型：
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作者：
Walch-Liu, Pia;Liu, Lai-Hua;Forde, Brian G.
众所周知，许多植物物种的根系利用NO3-形式的无机氮作为线索，在营养丰富的土壤斑块中启动局部根系增殖。我们在这里报道，在微摩尔浓度和基因型依赖的方式下，外源l -谷氨酸也能够引起拟南芥根系发育的复杂变化。l -谷氨酸在主根尖端被特异感知并抑制根尖分生组织的有丝分裂活性，但不干扰侧根的形成或生长。侧根在萌发后一段时间才获得对l -谷氨酸的敏感性，这表明它们对l -谷氨酸的反应能力受到发育调节。不同生态型拟南芥对l -谷氨酸的敏感性存在显著的自然差异，其中以C24最为敏感。生长素转运突变体aux1-7对l -谷氨酸的敏感性降低，表明l -谷氨酸与生长素信号传导之间可能存在相互作用。令人惊讶的是，AXR1位点的两个功能缺失突变体（AXR1 -3和AXR1 -12）对l -谷氨酸过敏。利用哺乳动物嗜离子性谷氨酸受体的激动剂和拮抗剂的药理学方法，无法提供它们的植物同源物在感知外源谷氨酸方面的作用的证据。我们讨论了l -谷氨酸感知的机制以及观察到的l -谷氨酸引起的根构型变化可能的生态意义。
The roots of many plant species are known to use inorganic nitrogen, in the form of NO3-, as a cue to initiate localized root proliferation within nutrient-rich patches of soil. We report here that, at micromolar concentrations and in a genotype-dependent manner, exogenous L-glutamate is also able to elicit complex changes in Arabidopsis root development. L-Glutamate is perceived specifically at the primary root tip and inhibits mitotic activity in the root apical meristem, but does not interfere with lateral root initiation or outgrowth. Only some time after emergence do lateral roots acquire L-glutamate sensitivity, indicating that their ability to respond to L-glutamate is developmentally regulated. Comparisons between different Arabidopsis ecotypes revealed a remarkable degree of natural variation in L-glutamate sensitivity, with C24 being the most sensitive. The aux1-7 auxin transport mutant had reduced L-glutamate sensitivity, suggesting a possible interaction between L-glutamate and auxin signaling. Surprisingly, two loss-of-function mutants at the AXR1 locus (axr1-3 and axr1-12) were hypersensitive to L-glutamate. A pharmacological approach, using agonists and antagonists of mammalian ionotropic glutamate receptors, was unable to provide evidence of a role for their plant homologs in sensing exogenous glutamate. We discuss the mechanism of L-glutamate sensing and the possible ecological significance of the observed L-glutamate-elicited changes in root architecture.