Transcriptome analysis of developing castor bean seeds and identification of ricinoleic acid biosynthesis genes

Abstract

Background Ricinoleic acid is a kind of unsaturated fatty acid in castor oil with wide application value. It is sourced from R. communis seed oil, where it is present in large amounts. However, there is little transcriptomic information on genes related to ricinoleic acid biosynthesis in castor bean.Results In order to better understand the regulation mechanism of ricinoleic acid biosynthesis, immature seeds at three developmental stages (15, 30, and 45 days after pollination) were collected. The results indicated that the accumulation of castor oil and ricinoleic acid increased gradually during seed development, and reached the maximum value at the late stages of seed development (45 days after pollination). Furthermore, RNA sequencing was conducted to analyze the transcriptome of the developing seeds at three developing stages. Totals of 9,875 differentially expressed genes were identified among the three time points. Based on the annotation information, 49 DEGs related to lipid biosynthesis were screened among all DEGs. Through cluster analysis of the 49 DEGs, ten genes with increasing FPKM values from seed development stages S1 to S3 were selected as candidate key enzymes, since they showed similar patterns of increase with castor oil accumulation and ricinoleic acid biosynthesis during seed development. The transcriptomic data of the 10 candidate key enzyme genes was further validated by qRT-PCR. Ultimately, a putative model of key genes correlated with ricinoleic acid accumulation was built.Conclusion Our study identified a series of key genes and revealed the proposed molecular mechanism of ricinoleic acid accumulation in castor seeds through the transcriptional analysis. It broadens our knowledge of ricinoleic acid biosynthesis and castor oil accumulation and also provides a theoretical foundation for the genetic engineering key genes that can improve the ricinoleic acid production in castor bean as well as other plants.