Differential Expression Of MicroRNA In Embryos Of Dry And Imbibed Maize Seeds

MicroRNAs, a new class of endogenous small and non-protein-coding RNA, playessential regulatory roles in plant growth, development and in response to biotic and abioticstresses. Seed germination plays a pivotal role during the life cycle of plants. As dry seedsimbibe water, energy metabolism and cellular repair are reprogrammed and miRNA-mediatedgene expression is involved in the reprogramming events. This research was aimed tounderstand the role of miRNA during seed imbibition process.Maize is one of the most important crops worldwide as well as a model plant forbiological research. However, the known miRNAs of maize is relatively low, especiallymiRNAs regulating seed germination. In this study, small RNA libraries constructed from dryand imbibed maize seed embryos were sequenced using the Illumina platform. The mainresults were as follows:1. Twenty-four conserved miRNA families were identified in both libraries. Sixteen ofthem showed significant expression differences between dry and imbibed seeds. TwelvemiRNA families, miR156, miR159, miR164, miR166, miR167, miR168, miR169, miR172,miR319, miR393, miR394and miR397, were significantly down-regulated; while fourfamilies, miR398, miR408, miR528and miR529, were significantly up-regulated in imbibedseeds compared to that in dry seeds.2. Putative novel maize miRNAs and their target genes were predicted. GO analysistarget genes was performed for novel miRNAs that were identified more than50times in thenormalized libraries. The result showed that carbohydrate metabolic genes were specificallyenriched in dry seeds, while the imbibed seeds were associated with a broad range offunctional categories including genes in amino acid biosynthesis, isomerase activity, ligaseactivity and others.3. The sequencing results were partially validated by quantitative RT-PCR for both conserved and novel miRNAs and predicted target genes.Our data suggested that diverse and complex miRNAs are involved in seed imbibitionprocess. miRNAs involved in plant hormone regulation may play important roles duringseed imbibition process.