The phytohormones jasmonate, gibberellin, salicylate, and ethylene regulate an interconnected reprogramming network integrating root development with plant responses against microbes. The establishment of mutualistic ectomycorrhizal symbiosis requires the suppression of plant defense responses against fungi as well as the modification of root architecture and cortical cell wall properties. Here, we investigated the contribution of phytohormones and their crosstalk to the ontogenesis of ectomycorrhizae (ECM) between grey poplar (Populus tremula x alba) roots and the fungus Laccaria bicolor. To obtain the hormonal blueprint of developing ECM, we quantified the concentrations of jasmonates, gibberellins, and salicylate via liquid chromatography-tandem mass spectrometry. Subsequently, we assessed root architecture, mycorrhizal morphology, and gene expression levels (RNA sequencing) in phytohormone-treated poplar lateral roots in the presence or absence of L. bicolor. Salicylic acid accumulated in mid-stage ECM. Exogenous phytohormone treatment affected the fungal colonization rate and/or frequency of Hartig net formation. Colonized lateral roots displayed diminished responsiveness to jasmonate but regulated some genes, implicated in defense and cell wall remodelling, that were specifically differentially expressed after jasmonate treatment. Responses to salicylate, gibberellin, and ethylene were enhanced in ECM. The dynamics of phytohormone accumulation and response suggest that jasmonate, gibberellin, salicylate, and ethylene signalling play multifaceted roles in poplar L. bicolor ectomycorrhizal development.

中文翻译：

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外生菌根真菌会改变对寄主根中茉莉酸，水杨酸酯，赤霉素和乙烯的敏感性。

茉莉酮，赤霉素，水杨酸酯和乙烯的植物激素调节相互连接的重编程网络，该网络将根发育与植物对微生物的反应整合在一起。建立互生的外生菌根共生关系需要抑制植物对真菌的防御反应，以及改变根部结构和皮层细胞壁特性。在这里，我们调查了植物激素及其串扰对灰白杨（Populus tremula x alba）根与真菌双色紫胶菌根外生菌根（ECM）本体发育的影响。为了获得发展中的ECM的激素蓝图，我们通过液相色谱-串联质谱法定量了茉莉酸酯，赤霉素和水杨酸酯的浓度。随后，我们评估了根的结构，菌根形态，存在或不存在双色乳杆菌的植物激素处理的杨侧根中的表达和基因表达水平（RNA测序）。水杨酸在ECM中期积累。外源植物激素处理影响了真菌定殖率和/或Hartig网的形成频率。殖民化的侧根显示出对茉莉酸的响应能力减弱，但是调节了一些基因，这些基因与防御和细胞壁重塑有关，在茉莉酸处理后这些基因特异性表达。在ECM中，对水杨酸盐，赤霉素和乙烯的反应增强。植物激素积累和响应的动力学表明，茉莉酸酯，赤霉素，水杨酸酯和乙烯信号在杨树双色外生菌根发育中起着多方面的作用。