Identification and characterization of miRNAs involved in adventitious branches formation of Gracilaria lichenoides in vitro

The main morphological response of Gracilaria lichenoides explants to wounding in vitro was the direct production of adventitious branches (ABs) within a short period rather than callus formation, similar to other seaweeds. However, the underlying mechanism remains unclear because of the lack of genome information. MicroRNAs (miRNAs) play a role in plant growth and development by targeting mRNAs for translational repression or cleavage. Here, we investigated small RNA-mediated regulation of ABs formation by examining the post-transcriptional profiles of different treatment samples of G. lichenoides using the Illumina sequencing platform. The results showed that miR156g-3p, miR2597, miR3447-3p, miR169j-3p and other miRNAs families play significant roles in ABs formation in G. lichenoides through their predicted targets, including phospholipase D (PLD), auxin response factor (ARF), protein phosphatase 2C (PP2C), CTR1 and adenylate isopentenyltransferase (IPT). In addition, we identified 30 putative unique Gracilariales miRNAs in two small RNA libraries that may be involved in ABs induction. Profiling of miRNAs and their target genes of G. lichenoides provide new insight on miRNAs networks involved in ABs formation in seaweed.