Regulation of coconut somatic embryogenesis: decoding the role of long non-coding RNAs

Long non-coding RNAs (lncRNAs)are transcripts longer than 200 nucleotides that lack significant protein coding potential and have been shown to regulate various biological processes. This study was designed to identify lncRNAs in coconut and their role in the process of somatic embryogenesis in coconut, a crop with high recalcitrance to in vitro culture. RNA-Seq data of coconut embryogenic calli of the West Coast Tall cultivar was exploited for in silico prediction of lncRNA. From a total of 6328 transcripts, which were annotated as uncharacterised or with no homology hits with the existing database, 5110 putative lncRNAs are identified. We also studied the relationship between lncRNAs, microRNAs (miRNAs)and mRNAs and found that some of the lncRNAs act as miRNA precursors, some as potential miRNA targets and some function as endogenous target mimics (eTMs)for miRNAs. Real-time quantitative PCR confirmed that 10 selected lncRNAs showed significant differences in the expression pattern in different stages of coconut somatic embryogenesis. Our results suggest the existence of diverse lncRNAs in coconut embryogenic calli, some of which are differentially expressed. The information generated in this study could be of great value in understanding the molecular mechanisms governing somatic embryogenesis in coconut.