Systemic and local regulation of legume nodulation
2008
Gresshoff, P.M. ([email protected]), The University of Queensland, Brisbane (Australia). Australian Research Council Centre of Excellence for Integrative Legume Research | Miyahara, A. | Nontachaiyapoom, S. | Indrasumunar, A. | Lin, Y, -H. | Reid, D. | Kinkema, M. | Biswas, B. | Jiang, Q. | Miyagi, M. | Li, D. | Lin, M.-H. | Carroll, B. | Chan, P.K. | Hirani, T. | Kereszt, A. | Ferguson, B.
Nodule formation in legumes is minimally controlled at two levels: the locally-acting perception of the mitogenic signal from the Rhizobium bacterium and the systemically-acting Autoregulation of Nodulation (AON), which involves closely related CLAVATA1-like LRR receptor kinases (GmNARK/LjHAR1/MtSUNN) expressed in phloem of most legume tissues; yet its biological activity in nodulation is almost exclusively within the leaf. To dissect AON, the soybean NARK promoter was analyzed to reveal tissue expression domains and a putative phloem specifying promoter domain. Increased nodulation, nitrogen gain and ability to nodulate effectively at sub-optimal Bradyrhizobium titres were achieved after overexpression of the GmNFR1a gene. Cloning of GmNFR1 and GmNFR5, complementation of mutants and nodulation efficiency analysis suggest that the AON circuit acts by perception of the NF signaling cascade and subsequently targeting its efficiency.
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