The Cultured Microbiome of Pollinated Maize Silks Shifts after Infection with Fusarium graminearum and Varies by Distance from the Site of Pathogen Inoculation

Thompson, Michelle E. H.; Shrestha, Anuja; Rinne, Jeffrey; Limay-Rios, Victor; Reid, Lana; Raizada, Manish N.

doi:10.3390/pathogens12111322

Cited by 2 publications

(1 citation statement)

References 164 publications

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“…Isolate R22 was also observed densely colonizing Fg hyphae, including near transition points where Fg was dying (turning from green to red). Isolate R22 contained genes for phenazine biosynthesis, acetoin biosynthesis, and colicin V biosynthesis (Thompson, 2023).…”

Section: Discussionmentioning

confidence: 99%

Protocols to enable fluorescence microscopy of microbial interactions on living maize silks (style tissue) that balance the requirements for containment, biological relevance, viability, and experimental accessibility

Thompson,

Raizada

2023

Preprint

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There is interest in studying microbes that colonize maize silks (style tissue, critical for reproduction) including the fungal pathogenFusarium graminearum(Fg) and its interactions with the microbiome and biocontrol agents.In plantaimaging of these interactions on living silks using confocal fluorescence microscopy would provide key insights. However, newly discovered microbes have unknown effects of on human health, and there are regulatory requirements to prevent the release of fluorescently-tagged microbes into the environment.Therefore, the microbe infection, colonization, and interaction stages on silks prior to microscopy must be contained. At the same time, silk viability must be maintained and experiments conducted that are biologically relevant (e.g. silks should remain attached to the cob), yet the silk tissue must be accessible to the researcher (i.e. not within husk leaves) and allow for multiple replicates. Here we present methods that meet these five contrasting criteria. We tested these methods usingFgand four silk-derived bacterial endophytes. The endophytes were previously known to have anti-Fgactivityin vitro, butin plantaobservations were lacking. In Method 1, a portion of the tip of a cob was dissected, and silks remained attached to the cob in a Petri dish. The cob was placed on a water agar disc to maintain hydration. DsRed-tagged bacteria and GFP-taggedFgwere inoculated onto the silks and incubated, allowing the two microbes to grow towards one another before staining with propidium iodide for confocal microscopy. A variation of the protocol was presented in Method 2, where detached silk segments were placed directly on water agar where they were inoculated with bacteria andFgto promote dense colonization, and to allow for many replicates and interventions such as silk wounding. The bacterial endophytes were successfully observed colonizingFghyphae, silk trichomes, and entering silks via cut ends and wounds. These protocols can be used to study other silk-associated microbes including several globally important fungal pathogens that enter maize grain through silks.

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Section: Discussionmentioning

confidence: 99%

Protocols to enable fluorescence microscopy of microbial interactions on living maize silks (style tissue) that balance the requirements for containment, biological relevance, viability, and experimental accessibility

Thompson,

Raizada

2023

Preprint

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The Microbiome of Fertilization-Stage Maize Silks (Style) Encodes Genes and Expresses Traits That Potentially Promote Survival in Pollen/Style Niches and Host Reproduction

Thompson,

Raizada

2024

Microorganisms

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Within flowers, the style channel receives pollen and transmits male gametes inside elongating pollen tubes to ovules. The styles of maize/corn are called silks. Fertilization-stage silks possess complex microbiomes, which may partially derive from pollen. These microbiomes lack functional analysis. We hypothesize that fertilization-stage silk microbiomes promote host fertilization to ensure their own vertical transmission. We further hypothesize that these microbes encode traits to survive stresses within the silk (water/nitrogen limitation) and pollen (dehydration/aluminum) habitats. Here, bacteria cultured from fertilization-stage silks of 14 North American maize genotypes underwent genome mining and functional testing, which revealed osmoprotection, nitrogen-fixation, and aluminum-tolerance traits. Bacteria contained auxin biosynthesis genes, and testing confirmed indole compound secretion, which is relevant, since pollen delivers auxin to silks to stimulate egg cell maturation. Some isolates encoded biosynthetic/transport compounds known to regulate pollen tube guidance/growth. The isolates encoded ACC deaminase, which degrades the precursor for ethylene that otherwise accelerates silk senescence. The findings suggest that members of the microbiome of fertilization-stage silks encode adaptations to survive the stress conditions of silk/pollen and have the potential to express signaling compounds known to impact reproduction. Overall, whereas these microbial traits have traditionally been assumed to primarily promote vegetative plant growth, this study proposes they may also play selfish roles during host reproduction.

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The Cultured Microbiome of Pollinated Maize Silks Shifts after Infection with Fusarium graminearum and Varies by Distance from the Site of Pathogen Inoculation

Cited by 2 publications

References 164 publications

Protocols to enable fluorescence microscopy of microbial interactions on living maize silks (style tissue) that balance the requirements for containment, biological relevance, viability, and experimental accessibility

Protocols to enable fluorescence microscopy of microbial interactions on living maize silks (style tissue) that balance the requirements for containment, biological relevance, viability, and experimental accessibility

The Microbiome of Fertilization-Stage Maize Silks (Style) Encodes Genes and Expresses Traits That Potentially Promote Survival in Pollen/Style Niches and Host Reproduction

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