The fungus does not transfer carbon to or between roots in an arbuscular mycorrhizal symbiosis

Abstract

Summary• Carbon transfer from fungus to plant in the arbuscular mycorrhizal (AM) symbiosis has been reported, but its significance and even its existence have been called into question and the issue remains controversial. We investigated carbon movement from fungus to plant and from one mycorrhizal root system to another via a common AM fungal network in monoxenic cultures to avoid limitations of some previous studies.• 13 C and 14 C labeled substrates were supplied to functioning in vitro AM mycorrhizas between Ri T-DNA transformed carrot ( Daucus carota ) roots and Glomus intraradices to follow carbon movement into and between host and fungal metabolite pools.• Fungal triacylglycerol and trehalose were labeled when permeant substrates were supplied to the extraradical mycelium (ERM), but host-specific compounds in the roots did not become labeled. When labeled glucose was provided to a donor root system, label moved to recipient roots via a common AM fungal network but remained in fungal compounds.• We conclude that carbon flow in the AM symbiosis is normally unidirectional from plant to fungus and that while carbon is translocated by the fungus from one metabolically active root system to another, it remains within the intraradical mycelium (IRM).

Soybean Metabolites Regulated in Root Hairs in Response to the Symbiotic BacteriumBradyrhizobium japonicum

“…Trehalose also accumulated in ectomycorrhized and endomycorrhized roots, particularly during drought stress (Schellenbaum et al, 1999;Pfeffer et al, 2004;Lopez et al, 2007). Genetic engineering of tobacco, potato, and tomato (Solanum lycopersicum) transformed with trehalose biosynthetic genes conferred higher resistance to drought, low and high temperature, salt, and oxidative stresses (Yeo et al, 2000;Almeida et al, 2005;Cortina and Culianez-Macia, 2005).…”

Physiological Significance of Network Organization in Fungi

“…Mathematical models of interconnected networks show that the exchange of energy resources provides an adaptive advantage to these organisms (49). Fungal interconnected networks form a contiguous lumen, which may facilitate information flow through biophysical principles, such as growth-induced mass flows and hydraulic coupling (30,31), or through cytoplasmic streaming, leading to significant advection (26,50,73).…”

Diversität der Ektomykorrhizen in verschieden artenreichen Laubbaumbeständen im Nationalpark Hainich (Thüringen)

“…Es konnte nachgewiesen werden, dass Kohlenstoffverbindungen und Nährstoffe zwischen den Pflanzen ausgetauscht wurden (Finlay und Read 1986aund 1986b, Graves et al 1997, Simard et al 1997, Simard et al 2002. Heute wird die Bedeutung der Vernetzung der Pflanzen über das Myzel (common mycelia network CMN) diskutiert und in Frage gestellt (Simard und Durall 2004, Taylor 2006, Peter 2006, Hodge 2006, Johnson et al 2005, Selosse et al 2006, da es auch Studien gibt, die den Transport von Kohlenstoffverbindungen innerhalb des Myzels, aber nicht in die verbundene Pflanze zeigen (Robinson und Fitter 1999, Wu et al 2001, Pfeffer et al 2004. Auch die Bedeutung des CMN für die Entwicklung der Naturverjüngung wird heute diskutiert.…”

“…Die ökologische Bedeutung der Vernetzung der Pflanzen durch das Pilzmyzel wird heute allerdings stark diskutiert (Simard und Durall 2004, Johnson et al 2005, Taylor 2006, Peter 2006, Hodge 2006, Selosse et al 2006, da einige Studien den Stofftransport zwischen verschiedenen Pflanzen nachweisen konnten (Finlay und Read 1986aund 1986b, Graves et al 1997, Simard et al 1997, Simard et al 2002 und andere Studien den Transport von Kohlenstoffverbindungen innerhalb des Myzels, aber nicht in die verbundene Pflanze zeigten (Robinson und Fitter 1999, Wu et al 2001, Pfeffer et al 2004. Auch die Bedeutung des Myzels für die Entwicklung der Naturverjüngung wird heute diskutiert.…”