Mycoheterotrophic germination of Pyrola asarifolia dust seeds reveals convergences with germination in orchids.
Dust seeds that germinate by obtaining nutrients from symbiotic fungi have evolved independently in orchids and 11 other plant lineages. The fungi involved in this 'mycoheterotrophic' germination have been identified in some orchids and non-photosynthetic Ericaceae, and proved identical to mycorrhizal fungi of adult plants. We investigated a third lineage, the Pyroleae, chlorophyllous Ericaceae species whose partial mycoheterotrophy at adulthood has recently attracted much attention. We observed experimental Pyrola asarifolia germination at four Japanese sites and investigated the germination pattern and symbiotic fungi, which we compared to mycorrhizal fungi of adult plants. Adult P. asarifolia, like other Pyroleae, associated with diverse fungal species that were a subset of those mycorrhizal on surrounding trees. Conversely, seedlings specifically associated with a lineage of Sebacinales clade B (endophytic Basidiomycetes) revealed an intriguing evolutionary convergence with orchids, some of which also germinate with Sebacinales clade B. Congruently, seedlings clustered spatially together, but not with adults. This unexpected transition in specificity and ecology of partners could support the developmental transition from full to partial mycoheterotrophy, but probably challenges survival and distribution during development. We discuss the physiological and ecological traits that predisposed to the repeated recruitment of Sebacinales clade B for dust seed germination.
Agro-environmental Science, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido 080-8555, Japan.
Yasushi
Y
Hashimoto
Agro-environmental Science, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido 080-8555, Japan.
Satoru
S
Fukukawa
Agro-environmental Science, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido 080-8555, Japan.
Ayako
A
Kunishi
Division of Genomics Research, Life Science Research Center, Gifu University, Yanagido 1-1, Gifu 501-1193, Japan.
Haruhisa
H
Suga
Centre d'Ecologie Fonctionnelle et Evolutive (CNRS, UMR 5175), 1919 Route de Mende, 34293 Montpellier Cedex 5, France.
Franck
F
Richard
Centre d'Ecologie Fonctionnelle et Evolutive (CNRS, UMR 5175), 1919 Route de Mende, 34293 Montpellier Cedex 5, France.
Mathieu
M
Sauve
Centre d'Ecologie Fonctionnelle et Evolutive (CNRS, UMR 5175), 1919 Route de Mende, 34293 Montpellier Cedex 5, France.
Marc-André
MA
Selosse
D001487:Basidiomycota / Q000145:classification / Q000235:genetics / Q000502:physiology; D005075:Biological Evolution; D003198:Computer Simulation; D017753:Ecosystem; D018525:Germination; D052836:Heterotrophic Processes; D007564:Japan; D038821:Mycorrhizae / Q000145:classification / Q000235:genetics / Q000502:physiology; D029595:Orchidaceae / Q000382:microbiology* / Q000502:physiology; D010802:Phylogeny; D031828:Pyrola / Q000382:microbiology / Q000502:physiology*; D036226:Seedlings / Q000502:physiology; D012639:Seeds / Q000382:microbiology / Q000502:physiology*; D013559:Symbiosis