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

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.

‘Cry‐for‐help’ in contaminated soil: a dialogue among plants and soil microbiome to survive in hostile conditions

“…A co‐adaptative strategy is established between recruited microorganisms and plants exposed to a particular stress, as observed for drought (Williams and de Vries, 2020 ), metal toxicity (Timm et al ., 2018 ), plant predation (Adaikpoh et al ., 2020 ) and nutrient limited growth conditions (Ham et al ., 2018 ) to support plant growth under these specific abiotic stressors (Liu et al ., 2020 ). The coumarin scopoletin breaks this paradigm, showing that a molecule exudated under iron starvation is also involved in counteracting pathogen proliferation and favouring the recruitment of beneficial microbes (Stringlis et al ., 2019 ).…”

Functional genomics study of Pseudomonas putida to determine traits associated with avoidance of a myxobacterial predator

“…The EtOAc extracts were dried in vacuo to produce crude extracts for LC–MS/MS analysis. The crude extracts from each condition were generated in triplicate and analyzed as previously described 92 . LC–MS/MS generated data was converted to.mzML files using MS-Convert, and the GNPS platform 58 was utilized as a dereplication tool to look for the library hits within publicly available natural products libraries.…”

Chromosomal organization of biosynthetic gene clusters suggests plasticity of myxobacterial specialized metabolism including descriptions for nine novel species:Archangium lansiniumsp. nov.,Myxococcus landrumussp. nov.,Nannocystis bainbridgeasp. nov.,Nannocystis poenicansasp. nov.,Nannocystis radixulmasp. nov.,Polyangium mundeleiniumsp. nov.,Pyxidicoccus parkwaysissp. nov.,Sorangium ateriumsp. nov.,Stigmatella ashevillenasp. nov

“…Isolation and genomic comparison of 20 isolated myxobacteria. Rhizospheric soil samples collected from shrubs and trees were screened for bacterial swarms using standard prey-baiting and filter paper degradation methods (18)(19)(20) to isolate environmental myxobacteria (Supplemental Figure 1) (21). Morphology screening of visible swarms facilitated isolation of myxobacteria from multiple genera with a specific focus on lesser-studied myxobacteria.…”