UMR INRA/Nancy Université 1136 Interactions Arbres/Micro-organismes, Institut Fédératif de Recherche 110 Genomique, Ecophysiologie, et Ecologie Fonctionnelles, INRA Nancy, F-54280 Champenoux, France.
Plant Physiol. 2009 Dec;151(4):1991-2005. doi: 10.1104/pp.109.147231. Epub 2009 Oct 23.
The early phase of the interaction between tree roots and ectomycorrhizal fungi, prior to symbiosis establishment, is accompanied by a stimulation of lateral root (LR) development. We aimed to identify gene networks that regulate LR development during the early signal exchanges between poplar (Populus tremula x Populus alba) and the ectomycorrhizal fungus Laccaria bicolor with a focus on auxin transport and signaling pathways. Our data demonstrated that increased LR development in poplar and Arabidopsis (Arabidopsis thaliana) interacting with L. bicolor is not dependent on the ability of the plant to form ectomycorrhizae. LR stimulation paralleled an increase in auxin accumulation at root apices. Blocking plant polar auxin transport with 1-naphthylphthalamic acid inhibited LR development and auxin accumulation. An oligoarray-based transcript profile of poplar roots exposed to molecules released by L. bicolor revealed the differential expression of 2,945 genes, including several components of polar auxin transport (PtaPIN and PtaAUX genes), auxin conjugation (PtaGH3 genes), and auxin signaling (PtaIAA genes). Transcripts of PtaPIN9, the homolog of Arabidopsis AtPIN2, and several PtaIAAs accumulated specifically during the early interaction phase. Expression of these rapidly induced genes was repressed by 1-naphthylphthalamic acid. Accordingly, LR stimulation upon contact with L. bicolor in Arabidopsis transgenic plants defective in homologs of these genes was decreased or absent. Furthermore, in Arabidopsis pin2, the root apical auxin increase during contact with the fungus was modified. We propose a model in which fungus-induced auxin accumulation at the root apex stimulates LR formation through a mechanism involving PtaPIN9-dependent auxin redistribution together with PtaIAA-based auxin signaling.
杨树与外生菌根真菌相互作用的早期阶段，即在共生建立之前，伴随着侧根（LR）发育的刺激。我们的目的是鉴定在杨树（Populus tremula x Populus alba）与外生菌根真菌 Laccaria bicolor 早期信号交换过程中调节 LR 发育的基因网络，重点关注生长素运输和信号通路。我们的数据表明，杨树和拟南芥（Arabidopsis thaliana）与 L. bicolor 相互作用时增加的 LR 发育不依赖于植物形成外生菌根的能力。LR 刺激与根尖生长素积累增加平行。用 1-萘基邻苯二甲酰亚胺阻断植物极性生长素运输抑制了 LR 发育和生长素积累。暴露于 L. bicolor 释放的分子的杨树根的寡核苷酸阵列转录谱显示了 2945 个基因的差异表达，包括极性生长素运输的几个成分（PtaPIN 和 PtaAUX 基因）、生长素结合（PtaGH3 基因）和生长素信号（PtaIAA 基因）。杨树 PtaPIN9 的转录本，拟南芥 AtPIN2 的同源物，以及几个 PtaIAAs 在早期相互作用阶段特异性积累。这些快速诱导基因的表达被 1-萘基邻苯二甲酰亚胺抑制。因此，在这些基因同源物缺陷的拟南芥转基因植物中，与 L. bicolor 接触时 LR 刺激减少或不存在。此外，在拟南芥 pin2 中，与真菌接触时根尖生长素的增加被改变。我们提出了一个模型，即真菌诱导的根尖生长素积累通过涉及 PtaPIN9 依赖性生长素再分配以及基于 PtaIAA 的生长素信号的机制刺激 LR 形成。
