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Symbioses: (including mycorrhizae, N-fixing, endophytes)

Symbioses: (including mycorrhizae, N-fixing, endophytes) . Questions. Discussions: Tatiana: posting paper and questions for this week Maria M: will be picking a paper to post for next week Paper due in 1 week Any questions?. Symbioses. Who are they and what do they do?

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Symbioses: (including mycorrhizae, N-fixing, endophytes)

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  1. Symbioses: (including mycorrhizae, N-fixing, endophytes)

  2. Questions • Discussions: • Tatiana: posting paper and questions for this week • Maria M: will be picking a paper to post for next week • Paper due in 1 week • Any questions?

  3. Symbioses • Who are they and what do they do? • Mycorrhizal fungi (http://mycorrhizas.info), Endophytes, and Nitrogen-fixing bacteria

  4. Ferns Gymnosperms Angiosperms

  5. Fungi

  6. Mycorrhizae • Define: Root-fungi association that is not pathogenic • A fungus that invades the root (cortex) • Roots typically have few to no root hairs, but fungus has better uptake • Mycelia are small in diameter • Excretes organic acids • Two main types: EM and VAM

  7. Distribution • Most plants have mycorrhizal associations • VAM is more common and ancestral ~80% of species • First records from 400 mya with early bryophytes • Fossils show association since plants first colonized land • EM found in ~10% of species in specific clades (e.g., Pinaceae, Fagales, Malvales, Cyperaceae, Caryophyllales)

  8. Distribution • Most plants have mycorrhizal associations (with other types evolving during Cretaceous) • Ericaceae (complex with VAM ancestral) • Orchid (single lineage) • Myco-heterotrophic plants with Exploitative: primitive, eudicots (e.g., Ericaceae) and monocots (e.g., Orchidaceae) • Nonmycorrhizal found in disturbed habitats with extreme conditions

  9. Mycorrhizae • Fungus: • Accesses water and minerals from the soil and decaying material and provides them in a form the plants can use (especially P) • Protects plants against pathogenic fungi • Plant: • Provides sugars, amino acids, and other organic materials • Dependent on coordinated growth of root and hyphae

  10. EM: Cortical and Epidermal • Ectomycorrhizal (EM): Basidiomycota, Ascomycota, Zygomycota; Gymnosperm & Angiosperm • Covers the root tip with a dense hyphal mantel • Hartig net: Hyphae invades intercellular spaces • Roots are short, branched and look swollen • Root hairs growth is suppressed

  11. EM: Monotropoid • Basidiomycota; Myco-heterotrophic ericoid plants

  12. EM: Arubtoid • Basidiomycota; Ericaceae

  13. VAM: A number of types • Endomycorrhizal/Vesicular arbuscular mycorrhizal (VAM): Glomeromycota; Most plants • The mantle is less obvious • Fungal hyphae invade intracellular spaces. They have arubscules (exchange) and vesicles (storage)

  14. Orchid • Basidiomycota; Orchidaceae (root, stem, exploitative - myco-heterotrophic)

  15. Ericoid • Ascomycota; Ericaceae

  16. But… • Fungi can be cheaters (pathogenic, parasitic, or saprophytic)

  17. Myco-heterotrophic • And so can plants • Orchidaceae (germination!) • Ericaceae

  18. Tripartite: A fungus, an underground orchid (Rhizanthella gardneri), and a Melaleuca (Melaleuca uncinata)

  19. Endophytes • Distribution: • Most plants • Especially studied in Poaceae • Found in shoots, roots and rhizomes • Fungi: differ in type of host, where they colonize, how they are transmitted, and fitness benefits to plant • Clavicipitaceous (class 1); grasses • Nonclavicipitaceous (class 1, 2, and 3); vascular and non vascular plants

  20. Endophytes • Poorly understood, • Protect plants against pathogens, growth enhancers, and tolerance of drought, pH, salinity, and temperature • Transmitted vertically (parent to offspring) via fungal hyphae or horizontally (among unrelated individuals) via spores • Live completely within host (spores produced on host senescence) • Important endophytic chemical?

  21. Nitrogen-fixing bacteria • Where is bulk of N? • Distribution: • Plants: Found in 4 orders in the subclade of the rosids I (Fabales, Rosales, Cucurbitales, Fagales) • Bacteria: Frankia and Rhizobium are often involved • Also ferns, cycads, and Gunnera with cyanobacteria associates

  22. Nitrogen-fixing bacteria • Plant roots form nodules where bacteria are located • N2 + 6 H -> 2 NH3 (anaerobic)

  23. Evolution of mixotrophy Selosse Tedersoo

  24. Question • Can undestory green plants obtain some of their carbon from overstory green plants via fungal networks? • Orchids: Shown already that mixotrophy can evolve near mycoheterotrophic taxa • Ericaceae: Can this model be used to predict mixotrophy taxa?

  25. Evolution of mixotrophy

  26. Ferns Gymnosperms Angiosperms

  27. Evolution of mixotrophy

  28. Question • Can undestory green plant obtain some of their carbon from overstory green plants via fungal networks? • Orchids: Shown already that mixotrophy can evolve from mycoheterotrophic taxa • Ericaceae: Can this model be used to predict mixotrophy evolution? • Used δ13C to show that Pyroleae have C signatures suggesting some C acquisition from fungi • Suggest 2 adaptations: vernal photosynthesis & fungal C exploitation

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