Unraveling the microRNA of Caragana korshinskii along a precipitation gradient on the Loess Plateau, China, using high-throughput sequencing.

Drought remains one of the main factors that negatively affect plant growth and development. Caragana korshinskii is widely distributed on the Loess Plateau, China, where it mediates soil and water loss and helps prevent desertification. However, little is known about the stress response mechanisms of C. korshinskii in water-starved environments. MicroRNAs (miRNAs) have been implicated in the regulation of plant responses to several types of biotic and abiotic stress. Here, we describe the miRNAs of wild C. korshinskii from Huangling, Yulin, and Dalad Banner, which occur along a precipitation gradient. Using next-generation sequencing technology, we obtained a total of 13 710 681, 15 048 945, and 15 198 442 reads for each location, respectively; after filtering and BLAST analysis, 490 conserved miRNAs and 96 novel miRNAs were characterized from the sRNAome data, with key functions determined using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses. We also designed stem-loop qRT-PCR to validate the expression patterns of 5 conserved miRNAs (miR390, miR398, miR530, miR2119, and miR5559) that obviously responded to water stress in plants grown both under natural and experimental water stress conditions and found that the expression levels of miR2119 and miR5559 were negatively correlated with their predicted target genes. This study is the first to identify miRNAs from wild C. korshinskii and provides a basis for future studies of miRNA-mediated gene regulation of stress responses in C. korshinskii.