Insights into the miRNA-mediated response of maize leaf to arsenate stress

Arsenic (As) contamination of soil and ground water poses serious threats to agricultural food production. MicroRNAs (miRNAs), a class of small non-coding RNAs play essential role in plant responses to environmental stress. In this study, we constructed two small RNA (sRNA) libraries from control and arsenate (50 μM AsV) treated maize leaves to identify AsV stress-responsive miRNAs. Using deep sequencing, we identified 22 (16 conserved and 6 novel) up- and 35 (33 conserved and 2 novel) down-regulated miRNAs from AsV challenged leaves. Gene ontology (GO) analyses reveal that predicted target genes of arsenic responsive miRNAs are associated with diverse biological processes such as plant growth and developmental (miR156s, miR166e-3p, miR166m, miR319b-3p), metabolic processes (miR159b-5p.3, zma_460, zma_468, zma_469), ROS generation (miR167d) and hormone signalling pathways (miR167d, miR159e.2, miR319b-3p). Moreover, we validated the expression patterns of selected miRNAs and their target genes by qRT-PCR. The miR319b-3p mediated down-regulation of GAMYB and low ARF3 transcript level might result in restricted shoot growth under AsV stress. The present work adds new insights into the underlying mechanisms of plant responses to arsenate stress at post-transcriptional level.