Transcriptome analysis of Sacha Inchi (Plukenetia volubilis L.) seeds at two developmental stages

Xiaojuan Wang,Ruling Wang,Aizhong Liu,Ronghua Xu

doi:10.1186/1471-2164-13-716

Abstract

BackgroundSacha Inchi (Plukenetia volubilis L., Euphorbiaceae) is a potential oilseed crop because the seeds of this plant are rich in unsaturated fatty acids (FAs). In particular, the fatty acid composition of its seed oil differs markedly in containing large quantities of α-linolenic acid (18C:3, a kind of ω-3 FAs). However, little is known about the molecular mechanisms responsible for biosynthesis of unsaturated fatty acids in the developing seeds of this species. Transcriptome data are needed to better understand these mechanisms.ResultsIn this study, de novo transcriptome assembly and gene expression analysis were performed using Illumina sequencing technology. A total of 52.6 million 90-bp paired-end reads were generated from two libraries constructed at the initial stage and fast oil accumulation stage of seed development. These reads were assembled into 70,392 unigenes; 22,179 unigenes showed a 2-fold or greater expression difference between the two libraries. Using this data we identified unigenes that may be involved in de novo FA and triacylglycerol biosynthesis. In particular, a number of unigenes encoding desaturase for formation of unsaturated fatty acids with high expression levels in the fast oil accumulation stage compared with the initial stage of seed development were identified.ConclusionsThis study provides the first comprehensive dataset characterizing Sacha Inchi gene expression at the transcriptional level. These data provide the foundation for further studies on molecular mechanisms underlying oil accumulation and PUFA biosynthesis in Sacha Inchi seeds. Our analyses facilitate understanding of the molecular mechanisms responsible for the high unsaturated fatty acids (especially α-linolenic acid) accumulation in Sacha Inchi seeds.

Highlights

Sacha Inchi (Plukenetia volubilis L., Euphorbiaceae) is a potential oilseed crop because the seeds of this plant are rich in unsaturated fatty acids (FAs)
Genes FAD2 and FAD3 were both located and expressed in ER in cells in association with storage lipid accumulation in cells [15]. These results indicated that genes FAD2 and FAD3 might play a major role in the formation of Polyunsaturated fatty acid (PUFA) in Sacha Inchi seeds
Functional categorization of differentially expressed genes reflected a number of important pathways, including the de novo FA biosynthesis, TAG assembly and the formation of PUFAs

Summary

Introduction

Sacha Inchi (Plukenetia volubilis L., Euphorbiaceae) is a potential oilseed crop because the seeds of this plant are rich in unsaturated fatty acids (FAs). Sacha Inchi (Plukenetia volubilis L.), known as Inca Inchi or mountain peanut, belongs to the family Euphorbiaceae It is a perennial oleaginous woody vine indigenous to tropical Peruvian jungles that lie at altitudes between 200 and 1500 m. Because PUFAs such as α-linolenic and linoleic acids cannot be synthesized in mammals, they are essential FAs (i.e., required in the diet) [4,5] These PUFAs exert a hypocholesterolemic effect against coronary heart disease and hypertension when used as food supplements, and are critical for the development of infants during pregnancy and breastfeeding periods [6,7,8]. Understanding the molecular mechanisms underlying seed development and lipid biosynthesis in Sacha Inchi may provide new insights for isolating novel genes and serve the use of genetic engineering to increase the α-linolenic content of traditional vegetable oils

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