The influence of maize genotype on the rhizosphere eukaryotic community

The microbiota colonizing the rhizosphere contributes to plant growth, productivity, carbon sequestration and phytoremediation. Several studies address plant-associated bacteria; however, few studies analyze the effect of plant genotype on the eukaryotic community. Here, we analyzed the eukaryotic composition of maize rhizosphere from three different plant landraces and one inbred line grown in the same soil (common garden approach). This experimental design, coupled with 18S rDNA gene amplicon sequencing, allowed us to test the influence of maize and its genotype on the rhizosphere's eukaryotic community. We found that plant growth modified the eukaryotic community in soil, as diversity comparisons between maize rhizosphere and unplanted soil revealed significantly different eukaryotic composition. Various genera of nematodes and fungi, predominantly bacterial feeding nematodes and mycorrhizal fungi among other taxa, were increased in the rhizosphere samples. We also observed that maize genotype differentially shaped the relative abundance of the following fungal families in the rhizosphere: Acaulosporaceae, Aspergillaceae, Chaetomiaceae, Claroideoglomeraceae, Corticiaceae, Mortierellaceae, Trichocomaceae and Trichomeriaceae. Thus, plant genotype has a selective influence on establishing fungal communities in the rhizosphere. This study emphasizes the importance of an integrated consideration of plant genetics for future agricultural applications of microbes to crops.

Maternal Immunization Confers Protection to the Offspring against an Attaching and Effacing Pathogen through Delivery of IgG in Breast Milk

Owing to immature immune systems and impaired colonization resistance mediated by the microbiota, infants are more susceptible to enteric infections. Maternal antibodies can provide immunity, with maternal vaccination offering a protective strategy. We find that oral infection of adult females with the enteric pathogen Citrobacter rodentium protects dams and offspring against oral challenge. Parenteral immunization of dams with heat-inactivated C. rodentium reduces pathogen loads and mortality in offspring but not mothers. IgG, but not IgA or IgM, transferred through breast milk to the intestinal lumen of suckling offspring, coats the pathogen and reduces intestinal colonization. Protective IgG largely recognizes virulence factors encoded within the locus of enterocyte effacement (LEE) pathogenicity island, including the adhesin Intimin and T3SS filament EspA, which are major antigens conferring protection. Thus, pathogen-specific IgG in breast milk induced during maternal infection or immunization protects neonates against infection with an attaching and effacing pathogen.