Introducing a new model for nitrogen fixation in cereal crops

Nitrogen-fixing microbial associations with cereals have been of intense interest for more than a century (Roesch et al., Plant Soil ۲۰۰۸;۳۰۲:۹۱–۱۰۴; Triplett, Plant Soil ۱۹۹۶;۱۸۶:۲۹–۳۸; Mus et al., Appl. Environ. Microbiol. ۲۰۱۶;۸۲:۳۶۹۸–۳۷۱۰; Beatty and Good, Science ۲۰۱۱;۳۳۳:۴۱۶–۴۱۷). A recent report demonstrated that an indigenous Sierra Mixe maize landrace, characterized by an extensive development of aerial roots that secrete large amounts of mucilage, can acquire ۲۸–۸۲% of its nitrogen from atmospheric dinitrogen (Van Deynze et al., PLoS Biol. ۲۰۱۸;۱۶: e۲۰۰۶۳۵۲). Although the Sierra Mixe maize landrace is unique in the large quantity of mucilage produced, other cereal crops secrete mucilage from underground and aerial roots and we hypothesize that this may represent a general mechanism for cereals to support associations with microbial diazotrophs. We propose a model for the association of nitrogen-fixing microbes with maize mucilage and identify the four main functionalities for such a productive diazotrophic association.