Comparative Transcriptome Analysis Reveals an Efficient Mechanism of α-Linolenic Acid in Tree Peony Seeds.

Qingyu Zhang,Md Rahman,Jiayuan Hu,Yanlong Zhang,Lihang Xie,Daoyang Sun,Aruna Kilaru,Lixia He,Lixin Niu,Rui Yu

doi:10.3390/ijms20010065

Abstract

Tree peony (Paeonia section Moutan DC.) species are woody oil crops with high unsaturated fatty acid content, including α-linolenic acid (ALA/18:3; >40% of the total fatty acid). Comparative transcriptome analyses were carried out to uncover the underlying mechanisms responsible for high and low ALA content in the developing seeds of P. rockii and P. lutea, respectively. Expression analysis of acyl lipid metabolism genes revealed upregulation of select genes involved in plastidial fatty acid synthesis, acyl editing, desaturation, and triacylglycerol assembly in seeds of P. rockii relative to P. lutea. Also, in association with ALA content in seeds, transcript levels for fatty acid desaturases (SAD, FAD2, and FAD3), which encode enzymes necessary for polyunsaturated fatty acid synthesis, were higher in P. rockii compared to P. lutea. Furthermore, the overexpression of PrFAD2 and PrFAD3 in Arabidopsis increased linoleic and ALA content, respectively, and modulated the final ratio 18:2/18:3 in the seed oil. In conclusion, we identified the key steps and validated the necessary desaturases that contribute to efficient ALA synthesis in a woody oil crop. Together, these results will aid to increase essential fatty acid content in seeds of tree peonies and other crops of agronomic interest.

Highlights

Tree peony belongs to the section Moutan DC, genus Paeonia, and family Paeoniaceae and is endemic to China
The comparison of seed transcriptomes of both species during development was limited to identifying crucial steps and the characterization of key enzymes, including desaturases involved in ALA synthesis
The final TAG content and composition is majorly influenced by the end product of plastidial fatty acid (FA) biosynthesis, the acyl editing through PC-derived pathway and their assembly in the endoplasmic reticulum (ER)

Summary

Introduction

Tree peony belongs to the section Moutan DC, genus Paeonia, and family Paeoniaceae and is endemic to China. Tree peony has attracted wide research interests due to the high amount of polyunsaturated fatty acids (PUFAs, >90%) in its seeds [1]. ALA is an essential omega-3 fatty acid (FA) for human health and nutrition, as it cannot be synthesized by humans and can only be obtained from diet [3]. Identifying and engineering plants to generate high levels of omega-3 FAs is a pertinent approach to meet the increasing dietary needs of humans [6]. To this extent, we aimed to elucidate the mechanisms by which tree peony species accumulate ALA in its seeds and develop tree peony species as an alternative source for the production of omega-3 FAs

Objectives

Methods

Results

Conclusion