Transcriptome sequencing discovers genes related to fatty acid biosynthesis in the seeds of Eucommia ulmoides

Abstract

Eucommia ulmoides is a focus of considerable attention because it is used to produce gutta-percha latex and raw materials for traditional Chinese medicine. The species has also been widely planted for vegetable oil production due to the high content of alpha-linolenic acid (ALA) in the seeds. However, little was known about fatty acid biosynthesis in the seeds. Here, we present transcriptome analyses that identified genes related to the fatty acid biosynthesis pathways in the seeds collected 70 and 160 days after flowering (DAF) from two varieties: ‘Huazhong No. 6’ (ALA content of 38.7 %) and ‘Huazhong No. 10’ (ALA content of 67.6 %). De novo assembly generated 96,469 unigenes with an average length of 690 bp. Among them, 11,260 unigenes identified by functional annotation against the Kyoto Encyclopedia of Genes and Genomes database were mapped to 117 metabolic pathways. 65 unigenes involved in fatty acid biosynthesis include 5 coding for 3-oxoacyl-ACP reductase, 2 coding for β-hydroxyacyl-ACP dehydratase, 10 coding for β-ketoacyl-ACP synthase II, and 2 coding for enoyl-ACP reductase I. Expression of the nine differentially expressed unigenes coding for major enzymes in fatty acid biosynthesis was validated by real-time fluorescent quantitative PCR (qPCR) using RNA from six seed stages (70, 88, 106, 124, 142, and 160 DAF) in ‘Huazhong No. 10’. The qPCR analysis showed that expression of these 9 unigenes all changed significantly at 88 DAF. This study provides a large-scale transcriptome annotation of E. ulmoides, which is fundamental information for further characterizing gene functionals involved in the process of seed development.