Evidence for miRNAs involved in the high-altitude responses of sainfoin (Onobrychis viciifolia) grown in the Qinghai-Tibetan plateau

Abstract

The identification of miRNAs and their functionality has mainly focused on the responses to single stresses or their combination under controlled conditions; however, the investigation of miRNAs under natural conditions is still limited. In the present study, miRNA-sequencing technology was used to identify differentially expressed miRNAs in the herbaceous plant, sainfoin (Onobrychis viciifolia), growing under the natural conditions present at low and high altitudes in the Qinghai-Tibetan plateau (QTP). In total, 298 known miRNAs and 190 novel putative miRNAs were identified, with miR319, miR166 and miR159 being the most highly represented miRNA families. In addition, results also revealed that 96 miRNAs, including 68 up-regulated and 28 down-regulated miRNAs, were differently expressed in sainfoin plants growing at a high-altitude, relative to those at a low altitude. Known miRNAs, such as miR156, miR160, miR397 and miR408, were among the up-regulated miRNAs, as well as novel-m0071 and novel-m0014. It is suggested that these miRNAs may play a crucial role in the adaption of sainfoin to the extreme natural environmental conditions present in the QTP. Additionally, a correlation analysis indicated that miR164 and miR5741 families had the largest number of target genes. As a result, they may play a primary role in the adaptation of sainfoin to adverse environmental conditions. The results obtained by stem-loop RT-qPCR analysis were consistent with the data obtained by high-throughput sequencing, confirming the accuracy of the miRNA sequencing. This is the first study to report on the identification of miRNAs in sainfoin under natural conditions, as well as differentially expressed miRNAs in sainfoin plants growing under natural contrasting environments, which will help elucidate the miRNA-mediated molecular mechanisms associated with the ability of sainfoin to adapt to the high-altitude environmental conditions in the QTP.