Differentially expressed microRNAs during solid endosperm development in coconut (Cocos nucifera L.)

MicroRNAs (miRNAs) are a class of 20–24 nt, endogenously expressed, non-coding RNAs that play important regulatory roles in plants and animals. To identify miRNAs potentially involved in tissue development and compound anabolism, we studied miRNA expression profiles in endosperm of coconut at different developmental stages. Based on the annotation in miRBase (release 10.1), we measured a total of 179 miRNAs in immature (95 expressed miRNAs) and mature tissues (176 expressed miRNAs) using microarrays, respectively. The comparative analyses on miRNA expression profiles between these two groups of tissues showed that 23 miRNAs were up-regulated and nine miRNAs were down-regulated in matured endosperm. We further confirmed the increased expression of four miRNAs and decreased expression of a miRNA in immature endosperm using real-time PCR. Moreover, we computationally predicted the target genes of 32 miRNAs with differential expression (p < 0.01), and identified the lowest-score targets of six miRNAs. Finally, we discussed the potential functional relevance of several differentially expressed miRNAs.