title: Seasonal and environmental changes of mycorrhizal associations and heterotrophy levels in mixotrophic Pyrola japonica (Ericaceae) growing under different light environments.
abstract: OBJECTIVE
  Mixotrophy is a strategy whereby plants acquire carbon both through photosynthesis and heterotrophic exploitation of mycorrhizal fungi. In Euro-American Pyroleae species studied hitherto, heterotrophy levels vary according to species, sites of study, and possibly light conditions. We investigated mycorrhizal association and mixotrophy in the Asiatic forest species Pyrola japonica, and their plasticity under different light conditions.
  
  
  METHODS
  Pyrola japonica was sampled bimonthly in sunny and shaded conditions from a deciduous broadleaf forest. We microscopically assessed the rate of fungal colonization and sequenced the ITS to identify the mycorrhizal fungi. We measured (13)C and (15)N isotopic abundances in P. japonica as compared with neighboring autotrophic and mycoheterotrophic plants, to evaluate P. japonica's heterotrophy level.
  
  
  RESULTS
  Pyrola japonica formed arbutoid mycorrhizas devoid of fungal mantles, with intracellular hyphal coils and a Hartig net. It tended to be more colonized by mycorrhizal fungi in spring and summer. Most associated fungi belonged to ectomycorrhizal taxa, and 84% of identified fungi were Russula spp. Rate of mycorrhizal colonization and Russula frequency tended to be higher in shaded conditions. Both δ(13)C and δ(15)N values of P. japonica were significantly higher in autotrophic plants, showing that about half of the carbon on average was received from mycorrhizal fungi. Both isotopic values negatively correlated with light availability, suggesting higher heterotrophy levels in shaded conditions.
  
  
  CONCLUSIONS
  The mixotrophic P. japonica undergoes changes in mycorrhizal symbionts and carbon nutrition according to light availability. Our results suggest that during Pyroleae evolution, a tendency to increased heterotrophy emerged in the Pyrola/Orthilia clade.
authors: Laboratory of Forest Pathology and Mycology, Graduate School of Bioresources, Mie University, Japan. m-yosuke@bio.mie-u.ac.jp
authors: Yosuke
authors: Y
authors: Matsuda
authors: Shoko
authors: S
authors: Shimizu
authors: Manami
authors: M
authors: Mori
authors: Shin-Ichiro
authors: S
authors: Ito
authors: Marc-André
authors: MA
authors: Selosse
mesh_terms: D052818:Autotrophic Processes; D002247:Carbon Isotopes / Q000032:analysis; D003624:Darkness; D029791:Ericaceae / Q000235:genetics / Q000378:metabolism / Q000382:microbiology*; D052836:Heterotrophic Processes; D038821:Mycorrhizae / Q000166:cytology / Q000235:genetics / Q000302:isolation & purification*; D012621:Seasons; D013559:Symbiosis
chemical_list: D002247:Carbon Isotopes