Abstract
Seed development has a critical role during the spermatophyte life cycle. In Brassica napus, a major oil crop, fatty acids are synthesized and stored in specific tissues during embryogenesis, and understanding the molecular mechanism underlying fatty acid biosynthesis during seed development is an important research goal. In this study, we constructed three small RNA libraries from early seeds at 14, 21, and 28 days after flowering (DAF) and used high-throughput sequencing to examine microRNA (miRNA) expression. A total of 85 known miRNAs from 30 families and 1160 novel miRNAs were identified, of which 24, including 5 known and 19 novel miRNAs, were found to be involved in fatty acid biosynthesis.bna-miR156b, bna-miR156c, bna-miR156g, novel_mir_1706, novel_mir_1407, novel_mir_173, and novel_mir_104 were significantly down-regulated at 21 DAF and 28 DAF, whereas bna-miR159, novel_mir_1081, novel_mir_19 and novel_mir_555 were significantly up-regulated. In addition, we found that some miRNAs regulate functional genes that are directly involved in fatty acid biosynthesis and that other miRNAs regulate the process of fatty acid biosynthesis by acting on a large number of transcription factors. The miRNAs and their corresponding predicted targets were partially validated by quantitative RT-PCR. Our data suggest that diverse and complex miRNAs are involved in the seed development process and that miRNAs play important roles in fatty acid biosynthesis during seed development.
Highlights
MicroRNAs are non-coding RNAs of ∼22 nucleotides in length that largely negatively regulate the translation of protein-coding gene(s) by binding to perfect complementarity sites in the 3′ untranslated regions (UTRs) of messenger RNAs, thereby targeting transcripts for cleavage or blocking their translation (Tarver et al, 2013). miRNAs are reported to be involved in a broad range of metabolic and physiological processes in plants, such as growth (Jones-Rhoades et al, 2006), development (Rubio-Somoza and Weigel, 2011) and responses to various stresses (Khraiwesh et al, 2012)
To examine the molecular mechanism of fatty acid biosynthesis during seed development, we investigated target genes related to the fatty acid biosynthesis pathway of differentially expressed miRNAs
It should be noted that there are some deficiencies in our study, as we focused mainly on activities between 14 and 28 days after flowering (DAF), the key period for lipid accumulation because lipid accumulation usually starts approximately 3 weeks after flowering and peaks microRNAs in Developing B. napus Seeds
Summary
MicroRNAs (miRNAs) are non-coding RNAs of ∼22 nucleotides in length that largely negatively regulate the translation of protein-coding gene(s) by binding to perfect complementarity sites in the 3′ untranslated regions (UTRs) of messenger RNAs (mRNAs), thereby targeting transcripts for cleavage or blocking their translation (Tarver et al, 2013). miRNAs are reported to be involved in a broad range of metabolic and physiological processes in plants, such as growth (Jones-Rhoades et al, 2006), development (Rubio-Somoza and Weigel, 2011) and responses to various stresses (Khraiwesh et al, 2012). MiRNAs are reported to be involved in a broad range of metabolic and physiological processes in plants, such as growth (Jones-Rhoades et al, 2006), development (Rubio-Somoza and Weigel, 2011) and responses to various stresses (Khraiwesh et al, 2012). There gulatory role of miRNAs is exemplified by their critical regulatory behavior at key steps in a variety of pathways, such as root (Wang et al, 2005), shoot (Golz, 2006), leaf (Kidner and Martienssen, 2004), and flower (Teotia and Tang, 2015) development and microRNAs in Developing B. napus Seeds cell fate (Carraro et al, 2006), and it is likely that their gene regulation function is as critical in maturing seeds as in other tissues(Martin et al, 2006). Understanding the alterations that occur in seeds at different developmental stages and establishing a regulatory network of miRNAs involved in seed development, especially with regard to fatty acid biosynthesis in oil crops, are essential for identifying the mechanism by which miRNAs regulate seed development
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