Latest reads: publications Jan/Feb 2021


With the winter weather outside, it's the perfect time to catch up on some scientific publications! Find and read below publications (and their abstract) from scientific journals by consortium members.

Coumarin Communication Along the Microbiome–Root–Shoot Axis

Stassen, M.J.J., Hsu, S.-H., Pieterse, C.M.J., Stringlis, I.A.
Trends in Plant Science Volume 26, Issue 2, February 2021, Pages 169-183

Plants shape their rhizosphere microbiome by secreting root exudates into the soil environment. Recently, root-exuded coumarins were identified as novel players in plant–microbiome communication. Beneficial members of the root-associated microbiome stimulate coumarin biosynthesis in roots and their excretion into the rhizosphere. The iron-mobilizing activity of coumarins facilitates iron uptake from the soil environment, while their selective antimicrobial activity shapes the root microbiome, resulting in promotion of plant growth and health. Evidence is accumulating that, in analogy to strigolactones and flavonoids, coumarins may act in microbiome-to-root-to-shoot signaling events. Here, we review this multifaceted role of coumarins in bidirectional chemical communication along the microbiome–root–shoot axis.


Bidirectional plant-mediated interactions between rhizobacteria and shoot-feeding herbivorous insects: a community ecology perspective

Friman, J., Pineda, A., van Loon, J.J.A., Dicke, M.
Ecological Entomology Volume 46, Issue 1, February 2021, Pages 1-10

Plants interact with various organisms, aboveground as well as belowground. Such interactions result in changes in plant traits with consequences for members of the plant-associated community at different trophic levels. Research thus far focussed on interactions of plants with individual species. However, studying such interactions in a community context is needed to gain a better understanding. Members of the aboveground insect community induce defences that systemically influence plant interactions with herbivorous as well as carnivorous insects. Plant roots are associated with a community of plant-growth promoting rhizobacteria (PGPR). This PGPR community modulates insect-induced defences of plants. Thus, PGPR and insects interact indirectly via plant-mediated interactions. Such plant-mediated interactions between belowground PGPR and aboveground insects have usually been addressed unidirectionally from belowground to aboveground. Here, we take a bidirectional approach to these cross-compartment plant-mediated interactions. Recent studies show that upon aboveground attack by insect herbivores, plants may recruit rhizobacteria that enhance plant defence against the attackers. This rearranging of the PGPR community in the rhizosphere has consequences for members of the aboveground insect community. This review focusses on the bidirectional nature of plant-mediated interactions between the PGPR and insect communities associated with plants, including (a) effects of beneficial rhizobacteria via modification of plant defence traits on insects and (b) effects of plant defence against insects on the PGPR community in the rhizosphere. We discuss how such knowledge can be used in the development of sustainable crop-protection strategies.

Temporal tracking of quantum-dot apatite across in vitro mycorrhizal networks shows how host demand can influence fungal nutrient transfer strategies.

Van't Padje A., Oyarte Galvez L., Klein M., Hink M.A., Postma M., Shimizu T., Kiers E.T.
The ISME Journal, 28 Sep 2020, 15(2):435-449

Arbuscular mycorrhizal fungi function as conduits for underground nutrient transport. While the fungal partner is dependent on the plant host for its carbon (C) needs, the amount of nutrients that the fungus allocates to hosts can vary with context. Because fungal allocation patterns to hosts can change over time, they have historically been difficult to quantify accurately. We developed a technique to tag rock phosphorus (P) apatite with fluorescent quantum-dot (QD) nanoparticles of three different colors, allowing us to study nutrient transfer in an in vitro fungal network formed between two host roots of different ages and different P demands over a 3-week period. Using confocal microscopy and raster image correlation spectroscopy, we could distinguish between P transfer from the hyphae to the roots and P retention in the hyphae. By tracking QD-apatite from its point of origin, we found that the P demands of the younger root influenced both: (1) how the fungus distributed nutrients among different root hosts and (2) the storage patterns in the fungus itself. Our work highlights that fungal trade strategies are highly dynamic over time to local conditions, and stresses the need for precise measurements of symbiotic nutrient transfer across both space and time.


Soil-borne legacies of disease in arabidopsis thaliana

Vismans, G., Spooren, J., Pieterse, C.M.J., Bakker, P.A.H.M., Berendsen, R.L.
Methods in Molecular Biology Volume 2232, 2021, Pages 209-218

The rhizosphere microbiome of plants is essential for plant growth and health. Recent studies have shown that upon infection of leaves with a foliar pathogen, the composition of the root microbiome is altered and enriched with bacteria that in turn can systemically protect the plant against the foliar pathogen. This protective effect is extended to successive populations of plants that are grown on soil that was first conditioned by pathogen-infected plants, a phenomenon that was coined “the soil-borne legacy.” Here we provide a detailed protocol for soil-borne legacy experiments with the model plant Arabidopsis thaliana after infection with the obligate biotrophic pathogen Hyaloperonospora arabidopsidis. This protocol can easily be extended to infection with other pathogens or even infestation with herbivorous insects and can function as a blueprint for soil-borne legacy experiments with crop species.

Volatiles from soil-borne fungi affect directional growth of roots

Moisan, K., Raaijmakers, J.M., Dicke, M., Lucas-Barbosa, D., Cordovez, V.
Plant Cell and Environment Volume 44, Issue 1, January 2021, Pages 339-345

Volatiles play major roles in mediating ecological interactions between soil (micro)organisms and plants. It is well-established that microbial volatiles can increase root biomass and lateral root formation. To date, however, it is unknown whether microbial volatiles can affect directional root growth. Here, we present a novel method to study belowground volatile-mediated interactions. As proof-of-concept, we designed a root Y-tube olfactometer, and tested the effects of volatiles from four different soil-borne fungi on directional growth of Brassica rapa roots in soil. Subsequently, we compared the fungal volatile organic compounds (VOCs) previously profiled with Gas Chromatography–Mass Spectrometry (GC–MS). Using our newly designed setup, we show that directional root growth in soil is differentially affected by fungal volatiles. Roots grew more frequently toward volatiles from the root pathogen Rhizoctonia solani, whereas volatiles from the other three saprophytic fungi did not impact directional root growth. GC–MS profiling showed that six VOCs were exclusively emitted by R. solani. These findings verify that this novel method is suitable to unravel the intriguing chemical cross-talk between roots and soil-borne fungi and its impact on root growth.