Detection of phosphate transporter genes from arbuscular mycorrhizal fungi in mature tree roots under experimental soil pH manipulation

The majority of terrestrial plant roots are colonized by arbuscular mycorrhizal (AM) fungi that, in exchange for carbon, provide plants with enhanced nutrient uptake — most notably inorganic phosphate (Pi). To mediate the uptake of Pi from the soil, AM fungi possess high affinity inorganic phosphate transporters (PTs). Under laboratory conditions, Pi concentrations have been shown to regulate AM fungal-specific PT gene expression. The relationship between PT expression and Pi in the field remains unexplored. Here we quantify AM fungal-specific PTs from maple tree roots in situ. In an effort to limit edaphic parameters, root samples were collected from manipulated forested plots that had elevated soil Pi availability, either through direct Pi application or elevating pH to lower exchangeable aluminum. The aim of the study was to examine AM fungal-specific PT gene expression both prior to and following soil Pi amendment; however, a direct correlation between soil Pi concentration and PT gene expression was not observed. PT transcripts were detected to a greater extent under elevated pH and, while our results are confounded by an overall low detection of PT genes (23 % of all samples collected), our findings raise interesting questions regarding the role of soil pH on PT function. Our study is a first step in understanding how edaphic properties influence PT expression and plant P acquisition in mature tree roots.