Changes in carbon allocation and expression of carbon transporter genes in Betula pendula Roth. colonized by the ectomycorrhizal fungus Paxillus involutus (Batsch) Fr.

Abstract

Comparative analyses of aspects of the carbon (C) physiology and the expression of C transporter genes in birch (Betula pendula Roth.) colonized by the ectomycorrhizal fungus Paxillus involutus (Batsch) Fr. were performed using mycorrhizal (M) and non‐mycorrhizal (NM) plants of similar foliar nutrient status. After six months of growth, the biomass of M plants was significantly lower than that of NM plants. Diurnal C budgets of both sets of plants revealed that M plants exhibited higher rates of photosynthesis and root respiration expressed per unit dry weight. However, the diurnal net C gain of M and NM plants remained similar. Ectomycorrhizal roots contained higher soluble carbohydrate pools and increased activity of cell wall invertase, suggesting that additional C was allocated to these roots and their ectomycorrhizal fungi consistent with an increased sink demand for C due to the presence of the mycobiont. In M roots, the expression of two hexose and one sucrose transporter genes of birch were reduced to less than one‐third of the expression level observed in NM roots. Analysis using a probe against the birch ribosomal internal transcribed spacer region revealed that M roots contained 22% less plant RNA than NM roots. As the expression of birch hexose and sucrose transporter genes was reduced to a much greater extent, this suggests that these specific genes were down‐regulated in response to alterations in C metabolism within M roots.

Fair Trade in the Underworld: the Ectomycorrhizal Symbiosis

“…Betula/Paxillus, Eucalyptus/Pisolithus, Pinus/Laccaria, Tilia/Tuber; Voiblet et al 2001;Podila et al 2002;Polidori et al 2002;Peter et al 2003;Johansson et al 2004;Menotta et al 2004;Duplessis et al 2005;Le Quéré et al 2005) provided new insights to existing models of ectomycorrhiza development and identified hundreds of ECM-regulated genes. As expected from previous studies Tagu et al 1996;Nehls et al 1998aNehls et al , b, 2001aNiini et al 1996;Kim et al 1998;Tarkka et al 1998;Wright et al 2000;Sundaram et al 2001;Charvet-Candela et al 2002), many cellular functions were found to be involved in symbiosis development, including genes involved in cell growth, differentiation and signaling, synthesis of cell wall and extracellular matrices, and primary metabolism ( Fig. 12.2).…”

Expression Analysis of Aquaporins from Desert Truffle Mycorrhizal Symbiosis Reveals a Fine-Tuned Regulation Under Drought

“…It has been hypothesized that the presence of a fungal sink may stimulate the rate of C assimilation (Tinker et al 1994). However, evidence in support of this hypothesis remains limited due to conflicting results (Nehls et al 2010;Wright et al 2000). The A values decreased less in H. almeriense M-DS than NM-DS plants ( Table 2).…”

The impact of ectomycorrhiza formation on monosaccharide transporter gene expression in poplar roots

“…In the case of ectomycorrhizas, regulation of gene expression could be related to an increased sink strength Wright et al, 2000), developmental processes or to compounds that act as a signal during symbiosis-related differentiation, for example phytohormones (Nehls et al, 1998a) or sugars (Nehls et al, 2001b;Nehls, 2004).…”