Biological nitrogen fixation in maize: optimizing nitrogenase expression in a root-associated diazotroph. (8th April 2020)

• Record Type: Journal Article
• Authors: Bloch, Sarah E; Clark, Rosemary; Gottlieb, Shayin S; Wood, L Kent; Shah, Neal; Mak, San-Ming; Lorigan, James G; Johnson, Jenny; Davis-Richardson, Austin G; Williams, Lorena; McKellar, Megan; Soriano, Dominic; Petersen, Max; Horton, Alana; Smith, Olivia; Wu, Leslie; Tung, Emily; Broglie, Richard; Tamsir, Alvin; Temme, Karsten
• Editors: Takahashi, Hideki
• Is Part Of: Journal of experimental botany. Volume 71:Number 15(2020)
• Page Start: 4591
• Page End: 4603
• Publication Date: 2020-04-08
• Subjects: Ammonium production -- biological nitrogen fixation -- corn rhizosphere -- diazotroph -- Kosakonia sacchari -- nitrogenase expression -- regulatory nodes; Botany -- Periodicals; Botany, Experimental -- Periodicals; Plant physiology -- Periodicals; 580
• DOI: 10.1093/jxb/eraa176
• Languages: English
• ISSNs: 0022-0957

Abstract

Abstract : Reprogramming the genetic regulation of nitrogen fixation and assimilation in a root-associated diazotroph to produce novel strains can restore ammonium production in the presence of exogenous nitrogen inputs. Abstract: Plants depend upon beneficial interactions between roots and root-associated microorganisms for growth promotion, disease suppression, and nutrient availability. This includes the ability of free-living diazotrophic bacteria to supply nitrogen, an ecological role that has been long underappreciated in modern agriculture for efficient crop production systems. Long-term ecological studies in legume–rhizobia interactions have shown that elevated nitrogen inputs can lead to the evolution of less cooperative nitrogen-fixing mutualists. Here we describe how reprogramming the genetic regulation of nitrogen fixation and assimilation in a novel root-associated diazotroph can restore ammonium production in the presence of exogenous nitrogen inputs. We isolated a strain of the plant-associated proteobacterium Kosakonia sacchari from corn roots, characterized its nitrogen regulatory network, and targeted key nodes for gene editing to optimize nitrogen fixation in corn. While the wild-type strain exhibits repression of nitrogen fixation in conditions replete with bioavailable nitrogen, such as fertilized greenhouse and field experiments, remodeled strains show elevated levels in the rhizosphere of corn in the greenhouse and field even in the presence of exogenous nitrogen. Such strains could be used in commercial applications to supply fixed nitrogen to cereal crops.