Identification of Genes Differentially Expressed in Extraradical Mycelium and Ectomycorrhizal Roots during Paxillus involutus-Betula pendula Ectomycorrhizal Symbiosis

Abstract

The development of ectomycorrhizal symbiosis leads to drastic changes in gene expression in both partners. However, little is known about the spatial regulation of symbiosis-regulated genes. Using cDNA array profiling, we compared the levels of expression of fungal genes corresponding to approximately 1,200 expressed sequenced tags in the ectomycorrhizal root tips (ECM) and the connected extraradical mycelium (EM) for the Paxillus involutus-Betula pendula ectomycorrhizal association grown on peat in a microcosm system. Sixty-five unique genes were found to be differentially expressed in these two fungal compartments. In ECM, a gene coding for a putative phosphatidylserine decarboxylase (Psd) was up-regulated by 24-fold, while genes coding for urea (Dur3) and spermine (Tpo3) transporters were up-regulated 4.1-and 6.2-fold in EM. Moreover, urea was the major nitrogen compound found in EM by gas chromatography-mass spectrometry analysis. These results suggest that (i) there is a spatial difference in the patterns of fungal gene expression between ECM and EM, (ii) urea and polyamine transporters could facilitate the translocation of nitrogen compounds within the EM network, and (iii) fungal Psd may contribute to membrane remodeling during ectomycorrhiza formation.Soils of temperate forests show both spatial and temporal heterogeneities in nutrient availability, particularly the availability of nitrogen, which is essential for growth processes (50). To access more nutrients, trees have developed a mycorrhizal strategy, in which the expanding mycelium of ectomycorrhizal fungi is able to explore a larger soil volume than the root alone (45). The ectomycorrhizal association is therefore a great advantage for controlling plant nutrient status and growth.The well-characterized structure of Paxillus involutus-Betula pendula ectomycorrhizae (7) is formed by three components: a sheath enclosing the root, an intraradicular network of hyphae, and an outwardly growing system of hyphae, which form essential connections with both the soil and the fruit bodies (50). The ectomycorrhizal mantle provides a structure suitable for nutrient storage and plays a key role in controlling nutrient transfer between the fungus and the plant through its intimate contact with the root surface (35). The extraradical mycelium (EM), which extends from the mantle as single hyphae or linear aggregates of such hyphae, is of additional importance, because these structural attributes form the connection between the mantle and the soil and thus provide pathways for nutrient exchange (41). The positive effect of ectomycorrhizal fungi on plant nutrition could be attributed largely to the activity of EM. The ability of P. involutus to take up and transfer nitrogen compounds to its host, B. pendula Roth, was demonstrated by 15

Gene Transcription in Lactarius quietus - Quercus petraea Ectomycorrhizas from a Forest Soil

“…Among these ESTs, 296 (48%) were similar to known plant or fungal genes, including genes of known function, putative open reading frames, and ESTs (Table 2). This result is in agreement with results obtained for other ECM EST projects: Pisolithus microcarpus-Eucalyptus globulus (47,55), Laccaria bicolorPseudotsuga menziesii (47), and Paxillus involutus-Betula pendula (26,45). Finally, the remaining ESTs showed no significant similarity to any other sequences in the NCBI databases, suggesting that these genes might be expressed only in Q. robur or L. quietus or only in samples from environmental conditions or that these ESTs corresponded to very rare transcripts that have not been found in previous EST projects.…”

“…Gene expression has also been studied separately in the ECM root tip and in the extraradical mycelium in the Paxillus involutusBetula pendula association (45,57). However, the transcriptome of environmental ECM samples has not yet been investigated.…”

A Signaling-Regulated, Short-Chain Dehydrogenase of Stagonospora nodorum Regulates Asexual Development

“…SNOG_11081 encodes a putative concanamycin-induced protein C. CipC was first identified as an accumulated protein in Aspergillus nidulans exposed to the antibiotic concanamycin A (36). Orthologues of CipC were also identified in other fungi; however, their function is unknown (2, 29, 37,43,64). The gene expression profile of CipC in planta showed maximal transcript abundance 1 day postinfection, which suggests that this gene may play a role during early infection.…”

Paxillus involutus Forms an Ectomycorrhizal Symbiosis and Enhances Survival of PtCOMT-modified Betula pendula in vitro

“…During mycorrhiza formation the epidermal cells of lateral roots extend radially, which has been suggested to increase the surface contact between the symbionts (BRUN et al, 1995). The distinct stages in the ECM development between B. pendula and P. involutus are covered by numerous changes in gene expression in both symbionts (JOHAN-SSON et al, 2004;LE QUÉRÉ et al, 2005;MOREL et al, 2005), including the genes related to lignin biosynthesis in B. pendula (LE QUÉRÉ et al, 2005).…”