Engineered plant control of associative nitrogen fixation

Abstract

<jats:title>Significance</jats:title> <jats:p> Inoculation of cereals with diazotrophic (N <jats:sub>2</jats:sub> -fixing) bacteria offers a sustainable alternative to the application of nitrogen fertilizers in agriculture. While natural diazotrophs have evolved multilayered regulatory mechanisms that couple N <jats:sub>2</jats:sub> fixation with assimilation of the product NH <jats:sub>3</jats:sub> and prevent release to plants, genetic modifications can permit excess production and excretion of NH <jats:sub>3</jats:sub> . However, a lack of stringent host-specificity for root colonization by the bacteria would allow growth promotion of target and nontarget plants species alike. Here, we exploit synthetic transkingdom signaling to establish plant host-specific control of the N <jats:sub>2</jats:sub> -fixation catalyst nitrogenase in <jats:italic>Azorhizobium caulinodans</jats:italic> occupying barley roots. This work demonstrates how partner-specific interactions can be established to avoid potential growth promotion of nontarget plants. </jats:p>