Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio B3, Ciudad Universitaria. CP 58030 Morelia, Michoacán, México.
Plant Cell Physiol. 2011 Mar;52(3):490-508. doi: 10.1093/pcp/pcr006. Epub 2011 Jan 19.
Serotonin (5-hydroxytryptamine) is a well-known neurotransmitter in mammals and is widely distributed in plants. This compound is synthesized from tryptophan and shares structural similarity with IAA. To date, little is known about the morphological, physiological and molecular responses of plants to serotonin. In this study, we characterized the effects of serotonin on growth and development in Arabidopsis thaliana seedlings. Gas chromatography-mass spectrometry (GC-MS) analysis showed that plants are able to take up serotonin from the growth medium, which coincided with greatly stimulated lateral root development at concentrations from 10 to 160 μM. In contrast, higher doses of serotonin repressed lateral root growth, primary root growth and root hair development, but stimulated adventitious root formation. To investigate the role of serotonin in modulating auxin responses, we performed experiments using transgenic Arabidopsis lines expressing the auxin-responsive marker constructs DR5:uidA, BA3:uidA and HS::AXR3NT-GUS, as well as a variety of Arabidopsis mutants defective at the AUX1, AXR1, AXR2 and AXR4 auxin-related loci. We found that serotonin strongly inhibited both DR5:uidA and BA3:uidA gene expression in primary and adventitious roots and in lateral root primordia. This compound also abolished the effects of IAA or naphthaleneacetic acid on auxin-regulated developmental and genetic responses, indicating an anti-auxin activity in the plant. Mutant analysis further showed that lateral root induction elicited by serotonin was independent of the AUX1 and AXR4 loci but required AXR1 and AXR2. Our results show that serotonin regulates root development probably by acting as a natural auxin inhibitor.
血清素（5-羟色胺）是哺乳动物中一种众所周知的神经递质，广泛分布于植物中。这种化合物是由色氨酸合成的，与 IAA 具有结构相似性。迄今为止，人们对植物对血清素的形态、生理和分子反应知之甚少。在这项研究中，我们描述了血清素对拟南芥幼苗生长和发育的影响。气相色谱-质谱联用（GC-MS）分析表明，植物能够从生长介质中摄取血清素，这与 10 至 160 μM 浓度下极显著的侧根发育相吻合。相比之下，较高剂量的血清素抑制侧根生长、主根生长和根毛发育，但刺激不定根形成。为了研究血清素在调节生长素反应中的作用，我们使用表达生长素响应标记物构建体 DR5:uidA、BA3:uidA 和 HS::AXR3NT-GUS 的转基因拟南芥系以及各种在 AUX1、AXR1、AXR2 和 AXR4 生长素相关位点有缺陷的拟南芥突变体进行了实验。我们发现，血清素强烈抑制了主根和侧根及侧根原基中 DR5:uidA 和 BA3:uidA 基因的表达。这种化合物还消除了 IAA 或萘乙酸对生长素调节的发育和遗传反应的影响，表明其在植物中具有抗生长素活性。突变体分析进一步表明，血清素诱导的侧根诱导不依赖于 AUX1 和 AXR4 基因座，但需要 AXR1 和 AXR2。我们的研究结果表明，血清素可能通过作为一种天然生长素抑制剂来调节根的发育。
