Two defined alleles of the LRR receptor kinase GmNARK in supernodulating soybean govern differing autoregulation of mycorrhization |
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Authors: | Claudia Meixner Gyorgy Vegvari Jutta Ludwig-Müller Hubert Gagnon Siegrid Steinkellner Christian Staehelin Peter Gresshoff Horst Vierheilig |
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Institution: | Institut für Pflanzenschutz (DAPP), Universität für Bodenkultur Wien, A-1190 Wien, Austria; Department Fruit Sciences, Faculty of Horticultural Sciences, Corvinus University of Budapest, H-1118 Budapest, Hungary; Institut für Botanik, Technische Universität Dresden, D-01062 Dresden, Germany; Department of Microbiology and Immunology, McGill University, Montreal H3A 2B4, Canada; State Key Laboratory of Biocontrol, School of Life Sciences, SunYat-Sen (Zhongshan) University, Guangzhou 510 275, China; ARC Centre of Excellence for Integrative Legume Research, University of Queensland, Brisbane Qld 4072, Australia |
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Abstract: | Plants regulate the extent of nodulation and root colonization by arbuscular mycorrhizal fungi (AMF), a phenomenon named autoregulation of symbiosis. We tested AMF colonization in split roots of various soybean genotypes Glycine max (L.) Merr. cv. Bragg, Enrei, Harosoy and Williams], where precolonization of one side of the split-root system by the AMF Glomus mosseae resulted in reduced mycorrhization of the other. AMF precolonization failed to control secondary mycorrhization in the supernodulating Bragg nonsense mutant nts1007 (Q106*), indicating that the GmNARK gene (predicted to encode a leucine-rich repeats (LRR) receptor kinase related to CLAVATA1 in Arabidopsis ) is involved in autoregulation of the AMF symbiosis. Here, we tested whether the allelic En6500 nonsense supernodulating mutant ( GmNARK K606*, derived from cv. Enrei) and supernodulating mutants of cv. Williams ( Nod1-3 and Nod2-4 ) with yet-undefined genetic lesions exhibit a similar symbiotic phenotype in mycorrhizal split-root systems. Surprisingly, these supernodulating mutants retained their ability to autoregulate AMF. To examine possible differences between two allelic mutants, we determined levels of IAA, abscisic acid, coumestrol, daidzein and genistein in mycorrhizal and uninoculated control roots. Compared with wild-type plants, both mutants showed reduced IAA accumulation in mycorrhizal roots. Roots of cv. Enrei and En6500 exhibited high levels of isoflavonoids not seen in Bragg or nts1007 . Taken together, these findings showed that supernodulation mutants, despite a common nodulation phenotype, differ in their ability to autoregulate AMF root colonization. This suggests either that the GmNARK gene product of some mutants is still partially functional (Q106* vs. K606*) or that varietal differences reflected in altered physiological responses suppress the loss of function. |
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