Identification of miRNAs and Their Target Genes in Taraxacum spp

MicroRNAs are endogenous noncoding RNA that play vital roles in all plant cellular metabolic processes by mediating target gene expression. To date, miRNAs in Taraxacum spp., which is an important industrial plant, have remained largely unknown. In the present study, 970 miRNAs from 399 families were identified in Taraxacum spp by conducting computational approaches. The most frequent miRNAs in Taraxacum spp was miR5021. According to the KEGG results, miR5021, miR838, and miR1533 are related to the terpene biosynthesis pathway, while miR5015b, and miR1436 are involved in the starch and sucrose biosynthesis pathways. Quantitative real-time PCR assay was performed to validate the expression levels of five predicted miRNAs and 3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase (HMGCR) and invertase as the target genes. Results indicated that the highest relative expression of miR1533 and miR1436 occurred in the flower, while the highest transcripts levels of miR5015b were observed in the stem. In addition, the higher relative expression level of the miR5021 and miR838 was consistent with the lower expression level of the HMGCR gene in all tissue, suggesting that miR5021 and miR838 are involved in regulating HMGCR gene expression. Since mevalonate pathway is the main source of isopentenyl pyrophosphate, which is used in the synthesis of rubber, miR5021 and miR838 play an important role in the production of rubber by regulating the expression of HMGCR enzyme. These findings will accelerate future perspective studies on the regulatory mechanisms of miRNAs in Taraxacum koksaghyz.