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Advisor(s)
Abstract(s)
In temperate forests, the roots of various tree species are colonized by ectomycorrhizal
fungi, which have a key role in the nitrogen nutrition of their hosts. However, not much is known
about the molecular mechanisms related to nitrogen metabolism in ectomycorrhizal plants. This
study aimed to evaluate the nitrogen metabolic response of oak plants when inoculated with the
ectomycorrhizal fungus Pisolithus tinctorius. The expression of candidate genes encoding proteins
involved in nitrogen uptake and assimilation was investigated in ectomycorrhizal roots. We found
that three oak ammonium transporters were over-expressed in root tissues after inoculation, while
the expression of amino acid transporters was not modified, suggesting that inorganic nitrogen
is the main form of nitrogen transferred by the symbiotic fungus into the roots of the host plant.
Analysis by heterologous complementation of a yeast mutant defective in ammonium uptake and
GFP subcellular protein localization clearly confirmed that two of these genes encode functional am-
monium transporters. Structural similarities between the proteins encoded by these ectomycorrhizal
upregulated ammonium transporters, and a well-characterized ammonium transporter from E. coli,
suggest a similar transport mechanism, involving deprotonation of NH4+, followed by diffusion of
uncharged NH3 into the cytosol. This view is supported by the lack of induction of NH4+ detoxifying
mechanisms, such as the GS/GOGAT pathway, in the oak mycorrhizal roots
Description
Keywords
mycorrhiza nitrogen ammonium transporter ectomycorrhizal fungi oak (cork oak)
Pedagogical Context
Citation
Sebastiana, M.; Serrazina, S.; Monteiro, F.; Wipf, D.; Fromentin, J.; Teixeira, R.; Malhó, R.; Courty, P.-E. Nitrogen Acquisition and Transport in the Ectomycorrhizal Symbiosis—Insights from the Interaction between an Oak Tree and Pisolithus tinctorius. Plants 2023, 12, 10
Publisher
MDPI