Systemic regulation of soybean nodulation by acidic growth conditions.
Mechanisms inhibiting legume nodulation by low soil pH, although highly prevalent and economically significant, are poorly understood. We addressed this in soybean (Glycine max) using a combination of physiological and genetic approaches. Split-root and grafting studies using an autoregulation-of-nodulation-deficient mutant line, altered in the autoregulation-of-nodulation receptor kinase GmNARK, determined that a systemic, shoot-controlled, and GmNARK-dependent mechanism was critical for facilitating the inhibitory effect. Acid inhibition was independent of aluminum ion concentration and occurred early in nodule development, between 12 and 96 h post inoculation with Bradyrhizobium japonicum. Biological effects were confirmed by measuring transcript numbers of known early nodulation genes. Transcripts decreased on both sides of split-root systems, where only one side was subjected to low-pH conditions. Our findings enhance the present understanding of the innate mechanisms regulating legume nodulation control under acidic conditions, which could benefit future attempts in agriculture to improve nodule development and biological nitrogen fixation in acid-stressed soils.
Australian Research Council Centre of Excellence for Integrative Legume Research, School of Agricultural and Food Sciences, University of Queensland, St. Lucia, Brisbane, Queensland 4072, Australia.
Meng-Han
MH
Lin
Peter M
PM
Gresshoff
Brett J
BJ
Ferguson
D000143:Acids / Q000494:pharmacology*; D000535:Aluminum / Q000633:toxicity; D000538:Aluminum Silicates / Q000494:pharmacology; D027321:Anion Transport Proteins / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant / Q000235:genetics; D005843:Geography; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D008954:Models, Biological; D000091285:Nitrate Transporters; D055170:Plant Root Nodulation / Q000187:drug effects* / Q000235:genetics; D018520:Plant Shoots / Q000187:drug effects / Q000502:physiology; D053204:Root Nodules, Plant / Q000187:drug effects / Q000235:genetics / Q000254:growth & development*; D012987:Soil / Q000737:chemistry; D013025:Glycine max / Q000187:drug effects / Q000235:genetics / Q000502:physiology*
D000143:Acids; D000538:Aluminum Silicates; D027321:Anion Transport Proteins; D000091285:Nitrate Transporters; D012987:Soil; C003760:vermiculite; D000535:Aluminum