Pri-miR172c encodes regulatory small peptides during soybean (Glycine max) nodule development

HN Su1,2, DX Li1, AH Hastwell1, MB Zhang1, XT Chu1, X Li3, PM Gresshoff1 and BJ Ferguson1

  1. Centre for Integrative Legume Research, School of Agricultural and Food Sciences, The University of Queensland, St. Lucia, Brisbane, QLD 4072, Australia
  2. National Navel Orange Engineering Research Center, Gannan Normal University, Ganzhou, Jiangxi 341000, China
  3. State Key Laboratory of Agricultural Microbiology, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China

MicroRNAs (miRNAs) are short regulatory RNAs that regulate many biological processes through cleavage of target mRNA, thereby suppressing translation. They are processed from primary transcripts called primary miRNAs (pri-miRNAs). The miR172c is an important non-coding RNA, which functions in nodulation regulation. It was demonstrated to promote nodule formation by transcriptionally repressing its target Nodule Number Control1 (NNC1), the protein product, which acts as a transcriptional repressor of the early nodulin gene ENOD40. Overexpressing miR172c significantly upregulates the expression level of ENOD40, ultimately giving rise to a phenotypic change of increased nodule number. These regulatory interactions have been confirmed at the post-translational level. Most interestingly, a number of recent studies revealed that some pri-miRNAs also encode small functional peptides, termed miRNA peptides (miPEPs). Whether pri-miR172c has a similar regulatory coding function remains unknown. Through bioinformatic analysis, we identified ten small open reading frames from pri-miR172c and found that their encoded amino acid sequences share a certain level of conservation with other legume species. Meanwhile, we are investigating their promoter regions for essential cis-regulatory elements that are critical for pri-miR172c translation. We selected six of these ORFs for further tissue-specific promoter activity analyses, with preliminary results showing that some exhibit nodule primordium-specific expression patterns. Preliminary results regarding the prediction validation and the implicated functions of miPEPs will be presented.