Integument-Specific Transcriptional Regulation in the Mid-Stage of Flax Seed Development Influences the Release of Mucilage and the Seed Oil Content.

Fabien Miart,Hervé Demailly,François Mesnard,Laurent Gutierrez,Loïc Dupont,Karine Pageau,Michelle Lequart,Nelly Dubrulle,Gaëlle Mongelard,Roland Molinié,Romain Roulard,Françoise Fournet,Jean-Xavier Fontaine,Brigitte Thomasset,Arezki Boudaoud,Sophie Bouton,Christopher Wattier,Olivier Van Wuytswinkel

doi:10.3390/cells10102677

Abstract

Flax (Linum usitatissimum L.) seed oil, which accumulates in the embryo, and mucilage, which is synthesized in the seed coat, are of great economic importance for food, pharmaceutical as well as chemical industries. Theories on the link between oil and mucilage production in seeds consist in the spatio-temporal competition of both compounds for photosynthates during the very early stages of seed development. In this study, we demonstrate a positive relationship between seed oil production and seed coat mucilage extrusion in the agronomic model, flax. Three recombinant inbred lines were selected for low, medium and high mucilage and seed oil contents. Metabolite and transcript profiling (1H NMR and DNA oligo-microarrays) was performed on the seeds during seed development. These analyses showed main changes in the seed coat transcriptome during the mid-phase of seed development (25 Days Post-Anthesis), once the mucilage biosynthesis and modification processes are thought to be finished. These transcriptome changes comprised genes that are putatively involved in mucilage chemical modification and oil synthesis, as well as gibberellic acid (GA) metabolism. The results of this integrative biology approach suggest that transcriptional regulations of seed oil and fatty acid (FA) metabolism could occur in the seed coat during the mid-stage of seed development, once the seed coat carbon supplies have been used for mucilage biosynthesis and mechanochemical properties of the mucilage secretory cells.

Highlights

Seeds development involves complex regulatory networks from the genomic to the phenomic scales which affect seed growth, quality and germination process [1,2,3,4]
We propose that during the mid-stage of seed development, oil, mucilage and gibberellic acid (GA) metabolism-related genes would be regulated by the coordinated use of carbon and by the mechanical forces induced by the expansion of the embryo on the seed coat and endosperm
We have shown the existence of differences in transcriptional regulations between recombinant inbred lines (RIL) occurring between 10 to 25 days post-anthesis (DPA) seed coat/endosperm (SCE), mainly in 25 DPA SCE, which affect a set of putative flax orthologs of genes involved in mucilage, seed oil and GA metabolism

Summary

Introduction

Seeds development involves complex regulatory networks from the genomic to the phenomic scales which affect seed growth, quality and germination process [1,2,3,4]. Oilseed species accumulate oils in their embryo as a major storage compound, and mucilage in the most external epidermal cell layer [4,5,6]. Mucilage of flax contains RG I (rhamnogalacturonans type I) with an important fraction of highly branched AXs (Arabinoxylans, [17,18,19]). These two main polysaccharidic fractions are deposited in the Mucilage Secretory Cells (MSCs) as successive layers. Flax seed is the main source of lignans in the form of complexed macromolecule in plants, among which secoisolariciresinoldiglucoside (SDG) is the most abundant [22]. The major fatty acid found in the flax seed oil is linolenic acid (ω-3, LIN, C18:3, 50–62%) and palmitic acid (PAL, C16:0, 4–6%), steric acid (STE, C18:0, 2–4.4%), oleic acid (OLE, C18:1, 10–24.2%), linoleic acid (ω-6, LIO, C18:2, 12–18%)

Objectives

Methods

Results

Conclusion