Molecular dialogue between arbuscular mycorrhizal fungi and the nonhost plant Arabidopsis thaliana switches from initial detection to antagonism

Abstract

Summary Approximately 29% of all vascular plant species are unable to establish an arbuscular mycorrhizal (AM) symbiosis. Despite this, AM fungi (Rhizophagus spp.) are enriched in the root microbiome of the nonhost Arabidopsis thaliana, and Arabidopsis roots become colonized when AM networks nurtured by host plants are available. Here, we investigated the nonhost–AM fungus interaction by analyzing transcriptional changes in Rhizophagus, Arabidopsis and the host plant Medicago truncatula while growing in the same mycorrhizal network. In early interaction stages, Rhizophagus activated the Arabidopsis strigolactone biosynthesis genes CCD7 and CCD8, suggesting that detection of AM fungi is not completely impaired. However, in colonized Arabidopsis roots, fungal nutrient transporter genes GintPT, GintAMT2, GintMST2 and GintMST4, essential for AM symbiosis, were not activated. RNA‐seq transcriptome analysis pointed to activation of costly defenses in colonized Arabidopsis roots. Moreover, Rhizophagus colonization caused a 50% reduction in shoot biomass, but also led to enhanced systemic immunity against Botrytis cinerea. This suggests that early signaling between AM fungi and Arabidopsis is not completely impaired and that incompatibility appears at later interaction stages. Moreover, Rhizophagus‐mediated defenses coincide with reduced Arabidopsis growth, but also with systemic disease resistance, highlighting the multifunctional role of AM fungi in host and nonhost interactions.

Endophytic fungus Falciphora oryzae promotes lateral root growth by producing indole derivatives after sensing plant signals

“…After recognizing plant signals, AM fungi secrete signalling molecules, such as chitooligosaccharides and lipochitooligosaccharides (Genre et al, 2013;Maillet et al, 2011). Interestingly, AM fungi induce the expression of the strigolactone biosynthesis genes CCD7 and CCD8 in nonhost Arabidopsis roots (Fernandez et al, 2019). Whether a signalling exchange occurs during endophyteplant interactions is still unknown (Brader, Compant, Mitter, Trognitz, & Sessitsch, 2014;Kusari, Hertweck, & Spiteller, 2012;Mhlongo, Piater, Madala, Labuschagne, & Dubery, 2018).…”

Ectomycorrhizal fungi induce systemic resistance against insects on a nonmycorrhizal plant in a CERK1‐dependent manner

“…To address our hypothesis, we tested whether Laccaria bicolor , an ECM fungus that colonizes a wide range of tree host species (Mueller, 1992), could trigger ISR on Arabidopsis thaliana , a nonmycorrhizal plant (Brundrett & Tedersoo, 2018). Some early responses associated with AM and ECM symbioses are retained in Arabidopsis (Ditengou et al ., 2015; Fernández et al ., 2019), and ISR against Botrytis , a fungal pathogen, was observed when Arabidopsis was grown in the presence of AM‐colonized Medicago (Fernández et al ., 2019). Arabidopsis lacks the CSP and is not naturally colonized by mycorrhizal fungi, and so allows for direct testing of whether ISR by mycorrhizal fungi is dependent on the CSP and colonization.…”

Interaction between arbuscular mycorrhizal fungi and Bacillus spp. in soil enhancing growth of crop plants

“…Strigolactone) which when perceived by the mycorrhizal fungi results in extensive hyphal branching leading to increase probability of root-fungal contact. Similarly, mycorrhizal fungi secrete certain signal molecules known as “myc factors” which can activate morphological and physiological changes in plants through induction of “sym pathway” [26, 30]. It has been deduced that seven proteins viz.…”