Unravelling a stearidonic acid-rich triacylglycerol biosynthetic pathway in the developing seeds of Buglossoides arvensis: A transcriptomic landscape

R V Sreedhar,L Prasanna Anjaneya Reddy,P Prasad,Malathi Srinivasan,Ram Rajasekharan

doi:10.1038/s41598-017-09882-y

Abstract

Buglossoides arvensis is an emerging oilseed crop that is rich in stearidonic acid (SDA) and has several potential applications in human health and nutrition. The molecular basis of SDA biosynthesis in this plant remains unknown due to lack of genomic information. To unravel key genes involved in SDA-rich triacylglycerol (TAG) biosynthesis, we performed transcriptome sequencing of pooled mRNA from five different developmental stages of B. arvensis seeds using Illumina NextSeq platform. De novo transcriptome assembly generated 102,888 clustered transcripts from 39.83 million high-quality reads. Of these, 62.1% and 55.54% of transcripts were functionally annotated using Uniprot-Viridiplantae and KOG databases, respectively. A total of 10,021 SSR-containing sequences were identified using the MISA tool. Deep mining of transcriptome assembly using in silico tools led to the identification of genes involved in fatty acid and TAG biosynthesis. Expression profiling of 17 key transcripts involved in fatty acid desaturation and TAG biosynthesis showed expression patterns specific to the development stage that positively correlated with polyunsaturated fatty acid accumulation in the developing seeds. This first comprehensive transcriptome analysis provides the basis for future research on understanding molecular mechanisms of SDA-rich TAG accumulation in B. arvensis and aids in biotechnological production of SDA in other oilseed crops.

Highlights

Long-chain ω-3 polyunsaturated fatty acids (LC ω-3 PUFA) are potent biological regulators with therapeutic and preventive properties for chronic diseases
The TAG content increased gradually and reached its maximum level at 30 days after flowering (DAF), which suggested that TAG biosynthesis usually occurs at a high rate after 6 DAF and progresses until 30 DAF
We identified a total of 176 transcripts mapped to lipid metabolism, of which Transcription Factors (TFs) belonging to NAC, MYB-related, C3H, bHLH, ARF, MYB and G2 like families were more predominant (Supplementary Fig. S2)

Summary

Introduction

Long-chain ω-3 polyunsaturated fatty acids (LC ω-3 PUFA) are potent biological regulators with therapeutic and preventive properties for chronic diseases. In addition to SDA, seed oil contains 42–48% ALA and 4.5–8% γ-linolenic acid (GLA)[4]. Its usage and market potential in genetically modified organism (GMO) free countries is still questionable Given all these factors, improving the B. arvensis crop with a high seed yield, oil content and quality will be a promising strategy for meeting the increasing ω-3 PUFA demand. Plant species that accumulate non-traditional fatty acids are wild and are not agronomically adapted. B. arvensis cultivars with a high seed yield and SDA content are developed and commercially cultivated in the UK4. We are currently in the process of developing high yielding lines with improved oil and SDA content through classical and modern molecular plant breeding techniques. Molecular mechanisms underlying non-traditional fatty acid (SDA and GLA) biosynthesis and accumulation in B. arvensis seed triacylglycerols are still unknown. Our group explored the TAG biosynthesis pathway in the developing seeds of ALA-rich Salvia hispanica (Chia) using a similar approach[17]

Methods

Results

Conclusion