ORIGINAL ARTICLE Identification of aluminum-responsive microRNAs in Medicago truncatula by genome-wide high-throughput sequencing

Abstract MicroRNAs (miRNAs) play important roles in response of plants to biotic and abiotic stresses. Aluminum (Al) toxicity is a major factor limiting plant growth in acidic soils. However, there has been limited report on the involvement of miRNAs in response of plants to toxic Al3?. To identify Al3?-responsive miRNAs at whole-genome level, high-throughput sequencing technology was used to sequence libraries constructed from root apices of the model legume plant Medicago truncatula treated with and without Al3?. High-throughput sequencing of the control and two Al3?-treated libraries led to generation of 17.1, 14.1 and 17.4 M primary reads, respectively. We identified 326 known miRNAs and 21 new miRNAs. Among the miRNAs, expression of 23 miRNAs was responsive to Al3?, and the majority of Al3?-responsive mRNAs was down-regulated. We further classified the Al3?-responsive miRNAs into three groups based on their expression patterns: rapid-responsive, late-responsive and sustained-responsive miRNAs. The majority of Al3?-responsive miRNAs belonged to the ‘rapid-responsive