Influence of zygomycete‐derivedD'orenone onIAAsignalling inTricholoma‐spruce ectomycorrhiza

Abstract

Despite the rising interest in microbial communication, only few studies relate to mycorrhization and the pool of potential morphogenic substances produced by the surrounding soil community. Here, we investigated the effect exerted by the C18 - ketone β-apo-13-carotenone, D'orenone, on the ectomycorrhizal basidiomycete Tricholoma vaccinum and its symbiosis with the economically important host tree, spruce (Picea abies). D'orenone is an early intermediate in the biosynthesis of morphogens in sexual development of mucoromycetes, the trisporoids. In the ectomycorrhizal fungus T. vaccinum, D'orenone increased the production and/or release of the phytohormone indole-3-acetic acid (IAA) which had been proposed to be involved in the mutual symbiosis. The induced expression of the fungal aldehyde dehydrogenase, Ald5 is associated with IAA synthesis and excretion. In the host tree, D'orenone modulated root architecture by increasing lateral root length and hypertrophy of root cortex cells, likely via changed IAA concentrations and flux. Thus, we report for the first time on carotenoid metabolites from soil fungi affecting both ectomycorrhizal partners. The data imply a complex network of functions for secondary metabolites which act in an inter-kingdom signalling in soil.

Enzymatic study on AtCCD4 and AtCCD7 and their potential to form acyclic regulatory metabolites

“…D'orenone has been shown to exert a regulatory function upon external application, affecting root hair growth in Arabidopsis (Schlicht et al , 2008). Moreover, this compound triggers indole-3-acetic acid (IAA) synthesis in the ectomycorrhizal basidiomycete Tricholoma vaccinum and promotes lateral root growth in the host tree spruce (Wagner et al , 2016). Taken together, our data do not support the hypothesis that AtCCD4 mediates the formation of signaling molecules from linear intermediates of the carotenoid biosynthesis pathway.…”

The Ectomycorrhizospheric Habitat of Norway Spruce and Tricholoma vaccinum: Promotion of Plant Growth and Fitness by a Rich Microorganismic Community

“…The microcosms were inoculated with T. vaccinum GK6514 and/or plus and minus mating types of the ubiquitous soil fungus Mucor mucedo (SF:JMRC:000620 or SF:JMRC:000621, JMRC, Jena, Germany). Strains of Mucor were chosen, because they may affect phytohormone signaling of fungi and trees and modulate their morphology (Wagner et al, 2016). Using a sterile stamp 7 mm diameter inocula of T. vaccinum were transferred from MMNb cultivation plates and for M. mucedo the same procedure was performed from SUP cultivation plates.…”

Editorial: Mycorrhizosphere Communication: Mycorrhizal Fungi and Endophytic Fungus-Plant Interactions

“…This complex relationship is reflected in the concept of the mycorrhizosphere, where plant roots and hyphae of the mycorrhizal partner encounter other soil microorganisms. These additional interactions in the vicinity of the root need to be considered in studies of cross-talk (Vannini et al, 2016; Wagner et al, 2016).…”

“…Moreover, ectomycorrhization can be reversed by associated fungi that produce IAA-inhibiting compounds (Hause and Saarschmidt, 2009). With soil zygomycetes, a tripartite interaction occurs in which the zygomycete-derived metabolite, D-orenone, induces a transporter that allows for increased excretion of IAA by the mycorrhizal fungus, T. vaccinum (Wagner et al, 2016). Soil bacteria are also capable of auxin biosynthesis, mostly upon tryptophan induction via root exudates.…”