miRNA-Mediated Posttranscriptional Regulation of Gene Expression in ABR17-Transgenic Arabidopsis thaliana Under Salt Stress

MicroRNAs (miRNAs) are a class of small endogenous RNAs conserved in eukaryotic organisms including plants. They suppress gene expression posttranscriptionally in many different biological processes. Previously, we reported salinity-induced changes in gene expression in transgenic Arabidopsis thaliana plants that constitutively expressed a pea abscisic acid-responsive (ABR17) gene. In the current study, we used microarrays to investigate the role of miRNA-mediated posttranscriptional gene regulation in these same transgenic plants in the presence and absence of salinity stress. We identified nine miRNAs that were significantly modulated due to ABR17 gene expression and seven miRNAs that were modulated in response to salt stress. The target genes regulated by these miRNAs were identified using sRNA target Base (starBase) degradome analysis and through 5'-RNA ligase-mediated rapid amplification of cDNA ends (RLM-RACE). Our findings revealed miRNA-mRNA interactions comprising regulatory networks of auxin response factor (ARF), argonaute 1 (AGO1), dicer-like proteins 1 (DCL1), SQUAMOSA promoter binding (SPB), NAC, APETALA 2 (AP2), nuclear factor Y (NFY), RNA-binding proteins, A. thaliana vacuolar phyrophosphate 1 (AVP1), and pentatricopeptide repeat (PPR) in ABR17-transgenic A. thaliana, which control physiological, biochemical, and stress signaling cascades due to the imposition of salt stress. Our results are discussed within the context of the effect of the transgene, ABR17, and the roles of miRNA expression may play in mediating plant responses to salinity.