Accumulation of eicosapolyenoic acids enhances sensitivity to abscisic acid and mitigates the effects of drought in transgenic Arabidopsis thaliana

Yaxiao Li,Xiaowei Yuan,Shiyang Liu,Baoxiu Qi,Fei Xia,Xinzheng Li

doi:10.1093/jxb/eru031

Abstract

IgASE1, a C18 Δ9-specific polyunsaturated fatty acid elongase from the marine microalga Isochrysis galbana, is able to convert linoleic acid and α-linolenic acid to eicosadienoic acid and eicosatrienoic acid in Arabidopsis. Eicosadienoic acid and eicosatrienoic acid are precursors of arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid, which are synthesized via the Δ8 desaturation biosynthetic pathways. This study shows that the IgASE1-expressing transgenic Arabidopsis exhibited altered morphology (decreased leaf area and biomass) and enhanced drought resistance compared to wild-type plants. The transgenic Arabidopsis were hypersensitive to abscisic acid (ABA) during seed germination, post-germination growth, and seedling development. They had elevated leaf ABA levels under well-watered and dehydrated conditions and their stomata were more sensitive to ABA. Exogenous application of eicosadienoic acid and eicosatrienoic acid can mimic ABA and drought responses in the wild type plants, similar to that found in the transgenic ones. The transcript levels of genes involved in the biosynthesis of ABA (NCED3, ABA1, AAO3) as well as other stress-related genes were upregulated in this transgenic line upon osmotic stress (300mM mannitol). Taken together, these results indicate that these two eicosapolyenoic acids or their derived metabolites can mitigate the effects of drought in transgenic Arabidopsis, at least in part, through the action of ABA.

Highlights

Very-long-chain polyunsaturated fatty acids (VLCPUFAs), such as arachidonic acid (ARA; 20:4 Δ5,8,11,14) and eicosapentaenoic acid (20:5 Δ5,8,11,14,17), are key molecules that participate in various biological processes in the cell
While studies show that the very-long-chain polyunsaturated fatty acid (VLCPUFA), such as ARA and other eicosapolyenoic acids, play important roles during biotic stress in plants (Bostock et al, 2011), hitherto there have been no reports of their effects on abiotic stress in plants
We utilized a transgenic Arabidopsis line expressing a fatty acid elongase gene from I. galbana that was specific for the two C18 Δ9 long-chain unsaturated fatty acids linoleic acid (LA) and ALA (Qi et al, 2002)

Summary

Introduction

Very-long-chain polyunsaturated fatty acids (VLCPUFAs), such as arachidonic acid (ARA; 20:4 Δ5,8,11,14) and eicosapentaenoic acid (20:5 Δ5,8,11,14,17), are key molecules that participate in various biological processes in the cell In animals these VLCPUFAs affect health and nutrition by regulating the expression of genes through changes in the rate of transcription or post-transcriptional modifications (Schroeder et al, 2008; Dimri et al, 2010; Barnes et al, 2012). Transgenic plants have been generated, including Arabidopsis (Qi et al, 2004), linseed (Abbadi et al, 2004), soybean (Kinney et al, 2004), and Brassica juncea (Wu et al, 2005; Cheng et al, 2010; Venegas-Calerón et al, 2010) These VLCPUFAs are not commonly found in higher plants, they are abundant in lipids of pathogens seriously affecting crop yield, including Phytophthora species and related oomycetes (Sun et al, 2013). These eicosapolyenoic acids can function as signalling molecules in various organisms (Rozhnova et al, 2003; Savchenko et al, 2010)

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