Myxobacterial Response to Methyljasmonate Exposure Indicates Contribution to Plant Recruitment of Micropredators.

Barbara I Adaikpoh,Sandeep K Misra,Shukria Akbar,D Cole Stevens,Hanan Albataineh,Joshua S Sharp

doi:10.3389/fmicb.2020.00034

Barbara I Adaikpoh, Sandeep K Misra + Show 4 more

Open Access

https://doi.org/10.3389/fmicb.2020.00034

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Journal: Frontiers in microbiology	Publication Date: Jan 28, 2020
Citations: 10	License type: CC BY 4.0

Affiliation: University of Mississippi

Abstract

Chemical exchanges between plants and microbes within rhizobiomes are critical to the development of community structure. Volatile root exudates such as the phytohormone methyljasmonate (MeJA) contribute to various plant stress responses and have been implicated to play a role in the maintenance of microbial communities. Myxobacteria are competent predators of plant pathogens and are generally considered beneficial to rhizobiomes. While plant recruitment of myxobacteria to stave off pathogens has been suggested, no involved chemical signaling processes are known. Herein we expose predatory myxobacteria to MeJA and employ untargeted mass spectrometry, motility assays, and RNA sequencing to monitor changes in features associated with predation such as specialized metabolism, swarm expansion, and production of lytic enzymes. From a panel of four myxobacteria, we observe the most robust metabolic response from plant-associated Archangium sp. strain Cb G35 with 10 μM MeJA impacting the production of at least 300 metabolites and inducing a ≥ fourfold change in transcription for 56 genes. We also observe that MeJA induces A. sp. motility supporting plant recruitment of a subset of the investigated micropredators. Provided the varying responses to MeJA exposure, our observations indicate that MeJA contributes to the recruitment of select predatory myxobacteria suggesting further efforts are required to explore the microbial impact of plant exudates associated with biotic stress.

Highlights

IntroductionComplex communities of microbes within rhizobiomes significantly benefit plant health (Berendsen et al, 2012; Bulgarelli et al, 2013; Muller et al, 2016; Richter-Heitmann et al, 2016; Sasse et al, 2018; Olanrewaju et al, 2019; Poudel et al, 2019)
Microbes belonging to one such group of bacteria considered beneficial, the Myxococcales, more colloquially referred to as myxobacteria, are micropredators that are ubiquitous in soils and capably predate microbes from genera that include plant pathogens (Dawid, 2000; Lueders et al, 2006; Perez et al, 2014; Zhou et al, 2014; Li et al, 2017; Livingstone et al, 2017; Cui et al, 2018; Petters et al, 2018; Lin et al, 2019)
If the plant phytohormone MeJA is involved in recruitment of myxobacteria to stave off pathogens, a shift in metabolism to produce predation-associated metabolites during exposure experiments might be observable

Summary

Introduction

Complex communities of microbes within rhizobiomes significantly benefit plant health (Berendsen et al, 2012; Bulgarelli et al, 2013; Muller et al, 2016; Richter-Heitmann et al, 2016; Sasse et al, 2018; Olanrewaju et al, 2019; Poudel et al, 2019). Myxobacteria have been observed to activate predatory features when exposed to exogenous, quorum signaling molecules typically produced by prey bacteria; this precedent for community signal perception and response makes myxobacteria excellent candidates for MeJA exposure experiments (Lloyd and Whitworth, 2017). Given their potential as pathogen-suppressing bacteria beneficial to root microbiomes, we sought to investigate how myxobacteria respond when exposed to ecologically equivalent titers of the phytohormone MeJA (Mueller et al, 1993; Blechert et al, 1995; Vijayan et al, 1998)

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Results

Conclusion