Transient Nod factor-dependent gene expression in the nodulation-competent zone of soybean (Glycine max [L.] Merr.) roots
Article first published online: 2 AUG 2012
© 2012 The Authors. Plant Biotechnology Journal © 2012 Society for Experimental Biology, Association of Applied Biologists and Blackwell Publishing Ltd
Plant Biotechnology Journal
Volume 10, Issue 8, pages 995–1010, October 2012
How to Cite
Hayashi, S., Reid, D. E., Lorenc, M. T., Stiller, J., Edwards, D., Gresshoff, P. M. and Ferguson, B. J. (2012), Transient Nod factor-dependent gene expression in the nodulation-competent zone of soybean (Glycine max [L.] Merr.) roots. Plant Biotechnology Journal, 10: 995–1010. doi: 10.1111/j.1467-7652.2012.00729.x
- Issue published online: 2 SEP 2012
- Article first published online: 2 AUG 2012
- Received 24 April 2012; revised 26 June 2012; accepted 28 June 2012.
- plant development;
All lateral organ development in plants, such as nodulation in legumes, requires the temporal and spatial regulation of genes and gene networks. A total mRNA profiling approach using RNA-seq to target the specific soybean (Glycine max) root tissues responding to compatible rhizobia [i.e. the Zone Of Nodulation (ZON)] revealed a large number of novel, often transient, mRNA changes occurring during the early stages of nodulation. Focusing on the ZON enabled us to discard the majority of root tissues and their developmentally diverse gene transcripts, thereby highlighting the lowly and transiently expressed nodulation-specific genes. It also enabled us to concentrate on a precise moment in early nodule development at each sampling time. We focused on discovering genes regulated specifically by the Bradyrhizobium-produced Nod factor signal, by inoculating roots with either a competent wild-type or incompetent mutant (nodC−) strain of Bradyrhizobium japonicum. Collectively, 2915 genes were identified as being differentially expressed, including many known soybean nodulation genes. A number of unknown nodulation gene candidates and soybean orthologues of nodulation genes previously reported in other legume species were also identified. The differential expression of several candidates was confirmed and further characterized via inoculation time-course studies and qRT-PCR. The expression of many genes, including an endo-1,4-β-glucanase, a cytochrome P450 and a TIR-LRR-NBS receptor kinase, was transient, peaking quickly during the initiation of nodule ontogeny. Additional genes were found to be down-regulated. Significantly, a set of differentially regulated genes acting in the gibberellic acid (GA) biosynthesis pathway was discovered, suggesting a novel role of GAs in nodulation.