Cell and Developmental Biology of Arbuscular Mycorrhiza Symbiosis

Abstract

The default mineral nutrient acquisition strategy of land plants is the symbiosis with arbuscular mycorrhiza (AM) fungi. Research into the cell and developmental biology of AM revealed fascinating insights into the plasticity of plant cell development and of interorganismic communication. It is driven by the prospect of increased exploitation of AM benefits for sustainable agriculture. The plant cell developmental program for intracellular accommodation of AM fungi is activated by a genetically defined signaling pathway involving calcium spiking in the nucleus as second messenger. Calcium spiking is triggered by chitooligosaccharides released by AM fungi that are probably perceived via LysM domain receptor kinases. Fungal infection and calcium spiking are spatiotemporally coordinated, and only cells committed to accommodating the fungus undergo high-frequency spiking. Delivery of mineral nutrients by AM fungi occurs at tree-shaped hyphal structures, the arbuscules, in plant cortical cells. Nutrients are taken up at a plant-derived periarbuscular membrane, which surrounds fungal hyphae and carries a specific transporter composition that is of direct importance for symbiotic efficiency. An elegant study has unveiled a new and unexpected mechanism for specific protein localization to the periarbuscular membrane, which relies on the timing of gene expression to synchronize protein biosynthesis with a redirection of secretion. The control of AM development by phytohormones is currently subject to active investigation and has led to the rediscovery of strigolactones. Nearly all tested phytohormones regulate AM development, and major insights into the mechanisms of this regulation are expected in the near future.

Phosphate Treatment Strongly Inhibits New Arbuscule Development But Not the Maintenance of Arbuscule in Mycorrhizal Rice Roots

“…These data are in accordance with the "birdsfoot" arbuscules described by Gutjahr and Parniske (2013) Feddermann et al, 2010), RAM2 (Wang et al, 2012), VAMP72s (Ivanov et al, 2012), SYP132A (Pan et al, 2016), EXO70I (Zhang et al, 2015), VTI12 (Lota et al, 2013), ERF1 (Devers et al, 2013), RED (Groth et al, 2013;Gutjahr and Parniske, 2013), RAM1/ATA (Rich et al, 2015), RAD1 (Park et al, 2015;Xue et al, 2015), and FatM (Bravo et al, 2016). Hence, P inhibition may be related to the functions of these genes.…”

The plasma membrane proteome of Medicago truncatula roots as modified by arbuscular mycorrhizal symbiosis

“…AM fungi notably assist the plant with the acquisition of mineral nutrients, mainly inorganic phosphate (Pi) and nitrogen (N) that are absorbed from the soil solution by the extra-radical mycelium. In turn, AM fungi are supplied with organic carbon forms essential for them to achieve their full life cycle (Gutjahr and Parniske 2013;Rich et al 2017;Luginbuehl et al 2017). As a result, AM fungi are obligate plant biotrophic microorganisms that have a global impact on plant mineral nutrition and on the carbon cycle.…”

“…The latter is referred to as the perifungal membrane around intracellular hyphae or the periarbuscular membrane around arbuscules (Harrison 2012). These tree-like hyphae are regarded as the main site of Pi and N delivery to the plant where they are traded for sugars generated by host photosynthesis Gutjahr and Parniske 2013). One of the first plant PM extension and remodeling cytological events in AM symbiosis occurs during infection of the root epidermis that involves the formation of an intracellular prepenetration apparatus (PPA) (Genre et al 2005.…”

The Starter Effect of Non-Symbiotic Microbial Bioproducts on Wheat

“…The symbiotic association between plants and fungi occurred over 400 million years ago (Bonfante, 2009), the interaction being as old as the appearance of plants on the earth (Gutjahr and Parniske, 2013) and partners have been selected following a long evolutionary process. Arbuscular mycorrhizas are symbiotic associations defined by arbuscules and vesicles as intracellular structures, formed within the root during the stages of development (Bonfante and Genre, 2010).…”