Molecular identification and analysis of arsenite stress-responsive miRNAs in rice.

Arsenic is highly toxic to living organisms including humans and plants. To investigate the responsive functions of miRNAs under arsenite stress, an indica rice, Minghui 86, has been deeply sequenced, and a total of 67 arsenite-responsive miRNAs were identified in rice seedling roots, of which 5 were further validated experimentally. The potential targets of those differential miRNAs include some transcription factors, protein kinases, and DNA- or metal ion-binding proteins that are associated with cellular and metabolic processes, pigmentation, and stress responses. The regulatory roles of four miRNAs on their targets in response to arsenite were further confirmed by real time RT-PCR. Interestingly, osa-miR6256 was originally characterized as a putative exonic miRNA, supporting the notion that miRNAs may also originate from some exons in plants. The first identification of arsenite-responsive miRNAs at the whole genome-wide level will broaden the current understanding of the molecular mechanisms of arsenite responses in rice.