AM Fungi: Biology and Ecology

AM Fungi: Biology and Ecology

• AM fungi are soil-borne microbes that form a symbiotic relationship with most vascular plants, exchanging nutrients for mutual benefit.
• They have existed for over 450 million years, suggesting a crucial role in plant colonization of land.
• AM fungi are aseptate and coenocytic with multinucleate spores containing storage lipids and a thick chitin wall.
• Their obligate symbiotic nature makes them unculturable and limits their study.
• AM fungi belong to the Glomeromycota phylum and exhibit polymorphic DNA sequences within their mycelia and spores, complicating species identification.
• Despite this, molecular analyses are revealing more information about their speciation.
• AM fungi demonstrate low host specificity, allowing a single plant to be colonized by numerous fungal species.
• While host preference exists, the lack of strict specificity contributes to the diversity and stability of agroecosystems.

AM Symbiosis: Biology and Functioning

• AM fungi colonize plant roots through spores, mycorrhizal root fragments, and extraradical hyphae.
• They form a mycelial network that extends into the surrounding soil.
• Upon encountering a host root, AM fungi engage in a signaling exchange with the plant, leading to changes in fungal development and plant gene expression.
• The AM symbiosis involves a complex interplay of molecular dialogue and plant regulatory genes.
• A characteristic fungal structure called an appressorium (or hyphopodium) forms on the root surface, marking the beginning of intracellular accommodation of the fungal symbiont.
• AM fungi play a significant role in nutrient uptake, particularly phosphorus, enhancing plant growth and productivity.
• They also contribute to soil structure and microbial communities.