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? – Mycorrhizal fungi ( Endophytes, and Nitrogen-fixing bacteria

Ferns Gymnosperms Angiosperms

Fungi

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

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)

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

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

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

EM: Monotropoid Basidiomycota; Myco-heterotrophic ericoid plants

EM: Arubtoid Basidiomycota; Ericaceae

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)

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

Ericoid Ascomycota; Ericaceae

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

Myco-heterotrophic And so can plants – Orchidaceae (germination!) – Ericaceae

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

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

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?

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

Nitrogen-fixing bacteria Plant roots form nodules where bacteria are located N H -> 2 NH 3 (anaerobic)

Evolution of mixotrophy Tedersoo Selosse

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?

Evolution of mixotrophy

Ferns Gymnosperms Angiosperms

Evolution of mixotrophy

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 δ 13 C to show that Pyroleae have C signatures suggesting some C acquisition from fungi Suggest 2 adaptations: vernal photosynthesis & fungal C exploitation