Abstract
PurposeArbuscular mycorrhizal fungi (AMF) play important roles in agriculture because of their ability to improve plant resilience against abiotic and biotic stresses. AMF as a technology to promote a more sustainable agriculture holds great potential, yet many factors affect the efficiency of this plant-microbe symbiosis leading to inconsistency in performance. The beneficial symbiosis between plants and AM fungi, also-known-as the mycorrhiza is promoted by strigolactones (SLs), carotenoid derivatives active as phytohormones and rhizosphere signals. Natural SLs are effective at extremely low concentrations, however their bioavailability in soil is scarce because their biosynthesis and exudation are plant-regulated, their degradation is fast and their mobility in soil is limited.MethodsThrough a broad synthetic chemistry approach, we explored how structurally diverse SL derivatives could improve hyphal branching of Gigaspora spp AMF under laboratory conditions and thus possibly boost mycorrhization into soil.ResultsWe tested twenty-six different derivatives and we could highlight structural enhancements to promote hyphal branching of in vitro germinated AMF spores at equal, and in some cases higher levels compared to natural SLs. A subset of these derivatives was tested for bioavailability, but no clear correlation was found with their activity on hyphal branching.ConclusionThis study suggests that we could use a targeted, chemical-design approach to synthetize new SL derivatives to enable enhanced promotion of mycorrhization and potentially enhanced bioavailability compared to natural SLs. Due to the roles of AMF in crop production systems, these results highlight new innovative approaches to promote sustainable agriculture.
Highlights
Strigolactones (SLs) are carotenoid derivatives synthetized in terrestrial plants and green algae (Lopez-Obando et al 2015; Waters et al 2017)
This study suggests that we could use a targeted, chemical-design approach to synthetize new SL derivatives to enable enhanced promotion of mycorrhization and potentially enhanced bioavailability compared to natural SLs
The results obtained with G. margarita followed a similar trend to G. rosea: SL4, SL15 and SL5 showed a strong and significant hyphal branching promotion effect compared to acetone other compounds
Summary
Strigolactones (SLs) are carotenoid derivatives synthetized in terrestrial plants and green algae (Lopez-Obando et al 2015; Waters et al 2017). They were recently characterized as phytohormones playing key roles in plant development (Sun et al 2016; Bennett et al 2016), plant architecture (Brewer et al 2016; Song et al 2017) and biotic and abiotic stress resistance (Torres-Vera et al 2014; Marzec 2016; Saeed et al 2017). It is not known yet how SL signaling works in fungi, as no D14 or MAX2 sequence homologues were isolated in the up-to-date, sole sequenced mycorrhizal fungus Rhizophagus irregularis (Besserer et al 2008; Bonfante and Genre 2015; Chen et al 2018a)
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