Transmitting silks of maize have a complex and dynamic microbiome

Abstract

In corn/maize, silks emerging from cobs capture pollen, and transmit resident sperm nuclei to eggs. There are > 20 million silks per U.S. maize acre. Fungal pathogens invade developing grain using silk channels, including Fusarium graminearum (Fg, temperate environments) and devastating carcinogen-producers (Africa/tropics). Fg contaminates cereal grains with mycotoxins, in particular Deoxynivalenol (DON), known for adverse health effects on humans and livestock. Fitness selection should promote defensive/healthy silks. Here, we report that maize silks, known as styles in other plants, possess complex and dynamic microbiomes at the critical pollen-fungal transmission interval (henceforth: transmitting style microbiome, TSM). Diverse maize genotypes were field-grown in two trial years. MiSeq 16S rRNA gene sequencing of 328 open-pollinated silk samples (healthy/Fg-infected) revealed that the TSM contains > 5000 taxa spanning the prokaryotic tree of life (47 phyla/1300 genera), including nitrogen-fixers. The TSM of silk tip tissue displayed seasonal responsiveness, but possessed a reproducible core of 7–11 MiSeq-amplicon sequence variants (ASVs) dominated by a single Pantoea MiSeq-taxon (15–26% of sequence-counts). Fg-infection collapsed TSM diversity and disturbed predicted metabolic functionality, but doubled overall microbiome size/counts, primarily by elevating 7–25 MiSeq-ASVs, suggestive of a selective microbiome response against infection. This study establishes the maize silk as a model for fundamental/applied research of plant reproductive microbiomes.

Patterns of Microbiome Composition Vary Across Spatial Scales in a Specialist Insect

“…Certain components of corn have a predictable and heritable microbiome ( Walters et al, 2018 ). In our case, WCR adults are likely closely associated with the microorganisms colonizing their diet, sharing taxa found both in corn silk and leaves ( Wagner et al, 2020 ; Khalaf et al, 2021 ). The most common family found in our samples, Enterobacteriaceae, is generally found in other insects feeding on corn plants as well ( Jones et al, 2019 ), suggesting a close association with corn.…”

Maisnarben – eine (un)bekannte traditionelle Arzneidroge

“…Andererseits wurde kürzlich berichtet, dass auch Mais im Bereich seiner weiblichen Blütenstände, v. a. auf den Narben über ein eigenes Mikrobiom verfügt, dass diese Organe vor dem Befall mit Fusarium spp. schützt 23 . Nicht zuletzt Sekundärprodukte dieser Mikrobiota wie z.…”

Microorganisms from corn stigma with biocontrol potential of Fusarium verticillioides

“…In addition, the microbiolized seeds reduced the fungal development in stored grains and stalk rot severity in the greenhouse by approximately 73% (strain ISD04). Khalaf et al (2021), applying MiSeq 16S rRNA gene sequencing of 328 open-pollinated silk samples (healthy/ fungi-infected), reported that maize silks possess complex and dynamic microbiomes with more than 5,000 taxa spanning the prokaryotic tree of life (47 phyla/1,300 genera).…”

“…Therefore, the silk emerging at the tips of corn cobs is critically important, not only for seed establishment but also because it is the gateway of entrance of carcinogenic mycotoxin-producing fungal pathogens that devastate millions of maize farmers (Johnson et al, 2007;Thompson and Raizada, 2018). Thus, the maize stigma has been described as the most efficient form of plant contamination by fungal pathogens invading the developing grain using the silk channels and causing disruption of the seeds and severe ear rot (Warfield and Davis, 1996;Khalaf et al, 2021).…”

“…In addition, many microorganisms and natural compounds derived from plants have fungistatic or fungicidal effects and can be used to manage plant diseases (Dias et al, 2020;Ahmadu et al, 2021;Matrose et al, 2021). However, despite the importance of maize silks to both reproduction and global grain disease, there are few studies in the literature about the effect of maize silk extracts and their microbiome for controlling plant diseases (Khalaf et al, 2021). Alam (2011), evaluating the antioxidant and antibacterial activities of ethanolic extract of Egyptian Maydis stigma against human pathogenic bacterial species, found an antibacterial activity of ethanolic extract of both upper and lower parts of maize silk.…”