| Autor: |
Haskett TL; Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom., Paramasivan P; Sainsbury Laboratory, University of Cambridge, Cambridge CB2 1LR, United Kingdom., Mendes MD; Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom., Green P; Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom., Geddes BA; Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom.; Department of Microbiological Sciences, North Dakota State University, Fargo, ND 58105., Knights HE; Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom., Jorrin B; Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom., Ryu MH; Synthetic Biology Center, Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139., Brett P; Biochemistry and Metabolism, The John Innes Centre, Norwich NR4 7UH, United Kingdom., Voigt CA; Synthetic Biology Center, Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139., Oldroyd GED; Sainsbury Laboratory, University of Cambridge, Cambridge CB2 1LR, United Kingdom., Poole PS; Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom. |
| Abstrakt: |
Engineering N2-fixing symbioses between cereals and diazotrophic bacteria represents a promising strategy to sustainably deliver biologically fixed nitrogen (N) in agriculture. We previously developed novel transkingdom signaling between plants and bacteria, through plant production of the bacterial signal rhizopine, allowing control of bacterial gene expression in association with the plant. Here, we have developed both a homozygous rhizopine producing (RhiP) barley line and a hybrid rhizopine uptake system that conveys upon our model bacterium Azorhizobium caulinodans ORS571 (Ac) 103-fold improved sensitivity for rhizopine perception. Using this improved genetic circuitry, we established tight rhizopine-dependent transcriptional control of the nitrogenase master regulator nifA and the N metabolism σ-factor rpoN, which drove nitrogenase expression and activity in vitro and in situ by bacteria colonizing RhiP barley roots. Although in situ nitrogenase activity was suboptimally effective relative to the wild-type strain, activation was specific to RhiP barley and was not observed on the roots of wild-type plants. This work represents a key milestone toward the development of a synthetic plant-controlled symbiosis in which the bacteria fix N2 only when in contact with the desired host plant and are prevented from interaction with nontarget plant species. |
