Functional characterisation of gibberellic acid in soybean (Glycine max) nodulation

XT Chu1, S Hayashi1, HN Su1,2, MB Zhang1, AH Hastwell1, D Tarkowaka3, PM Gresshoff1 and BJ Ferguson1

  1. Centre for Integrative Legume Research, School of Agriculture and Food Sciences, University of Queensland, St. Lucia, Brisbane, QLD, 4072, Australia
  2. National Navel Orange Engineering Research Center, Gannan Normal University, Ganzhou, Jiangxi 341000, China
  3. Department of Metabolomics, Centre of the Region Hann for Biotechnological and Agricultural Research, Faculty of Science, Palacky University in Olomouc, Slechtitelu 27, 783 71 Olomouc, Czech Republic

Legumes represent some of the most globally important food, feed and biofuel crops. Soybean (Glycine max) is the most economically significant legume species and is the third largest crop grown worldwide, following rice and wheat. Like most legume species, soybean is characterised by its ability to form root nodules in response to compatible nitrogen-fixing rhizobia bacteria (Bradyrhizobium japonicum). Nodule formation requires complex molecular mechanisms involving an array of signals, including the phytohormone gibberellic acid (gibberellin; GA). Nodule development is also tightly regulated by the host plant through additional signalling mechanisms. GAs appear to be required at different stages of nodulation, with their concentration highly regulated to achieve successful nodulation. Indeed, a window of GA appears to be required temporally and spatially, with too much or too little being inhibitory to nodule development. High throughput RNA-seq identified a set of differentially expressed GA oxidase genes in soybean. GmGA20ox a, GmGA3ox 1a, and GmGA2ox were all up-regulated in soybean roots inoculated with compatible rhizobia, indicating a requirement for these genes in nodulation; however, their precise roles in nodulation remain unclear. Our research aims to enhance the knowledge of GAs, and the individual GA oxidase genes, in soybean nodulation. Findings from our work will be presented.