Transcriptome and miRNAome analyses uncover the regulatory role of miR6155 in trichome development of tobacco

Glandular trichomes, which act as the first barrier against damage induced by insects and disease, can produce specialized metabolites that play important roles during plant development. However, the role played by microRNAs (miRNAs), which regulate many plant physiological processes, during trichome development is not unraveled in detail. In this study, we performed RNA sequencing (RNA-Seq) and small RNA sequencing assessments of tobacco trichome, leaf minus trichome (leaf-trichome), and leaf tissue to improve our understanding of the miRNA mechanisms regulating trichome development. Totally, we identified 270 differentially expressed miRNAs (DEMs) and 10,430 differentially expressed genes (DEGs) between trichome and leaf-trichome tissues. DEM targets were mainly associated with plant hormone signal transduction, plant–pathogen interactions, and the biosynthesis of secondary metabolites. Of these, 1233 miRNA–mRNA pairs were identified with reverse expression patterns. Next, we used dual-luciferase reporter (LUC) assays to reveal that several potential targets were significantly inhibited by corresponding miRNAs, including the transcription factors (TF) NAC021, AP2, MYB36, WRKY6 and TIFY10B. Further analysis showed that miR6155-WRKY6 might perform vital roles in trichome development, and that overexpression of miR6155 resulted in decreased trichome density. Taken together, these findings demonstrate that miRNAs may be involved in trichome development in tobacco, and they may advance our understanding of the regulation of trichome development mediated by miRNA and can help to improve genetic engineering of trichome regulation in plants.