Frettinger Patrick, Derory Jérémy, Herrmann Sylvie, Plomion Christophe, Lapeyrie Frédéric, Oelmüller Ralf, Martin Francis, Buscot François
Department of Terrestrial Ecology, University of Leipzig, Institute of Biology I, Johannisallee 21-23, 04103, Leipzig, Germany.
Planta. 2007 Jan;225(2):331-40. doi: 10.1007/s00425-006-0355-4. Epub 2006 Oct 3.
The formation of the ectomycorrhiza implies an alteration in gene expression of both the plant and fungal partners, a process which starts before the formation of any symbiotic interface. However, little is known on the regulation pattern occurring in different parts of the root system. Our experimental system consisting of a micropropagated oak with a hierarchical root system was shown to exhibit symbiosis functional traits prior to any mycorrhizal tissue differentiation after the inoculation with the basidiomycete Piloderma croceum. Using a cDNA array, the plant gene regulation was analyzed in the pre-mycorrhizal phase. Seventy-five transcripts showed differential expression in pre-mycorrhizal lateral and principal roots, and both root types exhibited different sets of responsive genes. For transcripts selected according to a statistical analysis, the alteration in gene expression was confirmed by RT-PCR and quantitative real-time PCR. Genes regulated in pre-mycorrhizal lateral roots displayed an almost identical expression in mycorrhizas. In contrast, genes regulated in pre-mycorrhizal principal roots were often regulated differently in ectomycorrhizas. Down-regulation affected most of the regulated genes involved in metabolism, whereas most of the regulated genes related to cell rescue functions, water regulation and defence response were up-regulated. Regulation of such genes could explain the increase of global resistance observed in mycorrhizal plants.
外生菌根的形成意味着植物和真菌共生伙伴的基因表达均发生改变，这一过程在任何共生界面形成之前就已开始。然而，对于根系不同部位所发生的调控模式却知之甚少。我们的实验系统由具有分层根系的微繁殖橡树组成，结果表明，在用担子菌黄绿皮伞接种后，在任何菌根组织分化之前，该系统就已表现出共生功能特性。利用cDNA阵列，对菌根形成前阶段的植物基因调控进行了分析。75个转录本在菌根形成前的侧根和主根中表现出差异表达，且两种根类型表现出不同的响应基因集。对于根据统计分析选择的转录本，通过RT-PCR和定量实时PCR证实了基因表达的改变。在菌根形成前的侧根中受调控的基因在菌根中表现出几乎相同的表达。相反，在菌根形成前的主根中受调控的基因在外生菌根中的调控方式往往不同。下调影响了大多数参与代谢的受调控基因，而大多数与细胞拯救功能、水分调节和防御反应相关的受调控基因则被上调。这些基因的调控可以解释在菌根植物中观察到的整体抗性增加现象。
