This study investigates the impact of the alteration of the monolignol biosynthesis pathway on the establishment of the in vitro interaction of poplar roots either with a mutualistic ectomycorrhizal fungus or with a pathogenic root-knot nematode. Overall, the five studied transgenic lines downregulated for caffeoyl-CoA O-methyltransferase (CCoAOMT), caffeic acid O-methyltransferase (COMT), cinnamoyl-CoA reductase (CCR), cinnamyl alcohol dehydrogenase (CAD) or both COMT and CAD displayed a lower mycorrhizal colonisation percentage, indicating a lower ability for establishing mutualistic interaction than the wild-type. The susceptibility to root-knot nematode infection was variable in the five lines, and the CAD-deficient line was found to be less susceptible than the wild-type. We discuss these phenotypic differences in the light of the large shifts in the metabolic profile and gene expression pattern occurring between roots of the CAD-deficient line and wild-type. A role of genes related to trehalose metabolism, phytohormones, and cell wall construction in the different mycorrhizal symbiosis efficiency and nematode sensitivity between these two lines is suggested. Overall, these results show that the alteration of plant metabolism caused by the repression of a single gene within phenylpropanoid pathway results in significant alterations, at the root level, in the response towards mutualistic and pathogenic associates. These changes may constrain plant fitness and biomass production, which are of economic importance for perennial industrial crops such as poplar.

中文翻译：

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苯丙烷途径的改变会影响杨树的外生菌根定植能力和对根结线虫的敏感性。

这项研究调查了单木酚醇生物合成途径的改变对建立杨树根与互生外生菌根真菌或致病性根结线虫的体外相互作用的影响。总体而言，研究的五个转基因品系的咖啡酰辅酶A-甲基转移酶（CCoAOMT），咖啡酸邻甲基转移酶（COMT），肉桂酰辅酶A还原酶（CCR），肉桂醇脱氢酶（CAD）或COMT和CAD均下调显示出较低的菌根定植百分比，这表明与野生型相比，建立相互互动的能力较低。在这五个品系中，根结线虫感染的易感性是可变的，并且发现CAD缺陷品系比野生型不易感染。我们根据代谢缺陷和CAD缺乏系与野生型的根之间发生的基因表达模式的大变化来讨论这些表型差异。提出了与海藻糖代谢，植物激素和细胞壁结构有关的基因在这两株系之间不同的菌根共生效率和线虫敏感性中的作用。总体，这些结果表明，由苯基丙烷途径内单个基因的抑制所引起的植物代谢的改变在根水平上导致对互惠和病原体应答的显着改变。这些变化可能会限制植物适应性和生物量生产，这对于多年生工业作物（如杨树）具有重要的经济意义。