12-Oxo-Phytodienoic Acid Accumulation during Seed Development Represses Seed Germination inArabidopsis

Anuja Dave,Fabián E Vaistij,Vasilios M.E Andriotis,M Luisa Hernández,Zhesi He,Tony R Larson,Ian A Graham

doi:10.1105/tpc.110.081489

Abstract

Arabidopsis thaliana COMATOSE (CTS) encodes an ABC transporter involved in peroxisomal import of substrates for β-oxidation. Various cts alleles and mutants disrupted in steps of peroxisomal β-oxidation have previously been reported to exhibit a severe block on seed germination. Oxylipin analysis on cts, acyl CoA oxidase1 acyl CoA oxidase2 (acx1 acx2), and keto acyl thiolase2 dry seeds revealed that they contain elevated levels of 12-oxo-phytodienoic acid (OPDA), jasmonic acid (JA), and JA-Ile. Oxylipin and transcriptomic analysis showed that accumulation of these oxylipins occurs during late seed maturation in cts. Analysis of double mutants generated by crossing cts with mutants in the JA biosynthesis pathway indicate that OPDA, rather than JA or JA-Ile, contributes to the block on germination in cts seeds. We found that OPDA was more effective at inhibiting wild-type germination than was JA and that this effect was independent of CORONATINE INSENSITIVE1 but was synergistic with abscisic acid (ABA). Consistent with this, OPDA treatment increased ABA INSENSITIVE5 protein abundance in a manner that parallels the inhibitory effect of OPDA and OPDA+ABA on seed germination. These results demonstrate that OPDA acts along with ABA to regulate seed germination in Arabidopsis.

Highlights

Peroxisomal b-oxidation has multiple roles in plant cells, including catabolism of straight-chain fatty acids derived from storage and membrane lipids, catabolism of branched-chain amino acids, and synthesis of indole-3-acetic acid and jasmonic acid (JA)
Peroxisomal enzymes that catalyze the core set of b-oxidation reactions are acyl-CoA oxidase (ACX), multifunctional protein (MFP), and L-3-ketoacyl-CoA thiolase (KAT). cts, acx1 acx2, and kat2 mutant seeds are defective in seedling establishment as they are unable to catabolize fatty acids derived from storage oil and require exogenous sucrose as an alternate carbon source to fuel growth until the mutant seedlings become photoautotrophic (Hayashi et al, 1998, 2002; Germain et al, 2001; Zolman et al, 2001; Footitt et al, 2002; Adham et al, 2005; Pinfield-Wells et al, 2005)
We tested the effect of exogenous oxo-phytodienoic acid (OPDA) on germination of coi1-16 seeds and found that they respond to OPDA treatment with reduction of germination at 10 and 50 mM concentrations (Figure 8A)

Summary

Introduction

Peroxisomal b-oxidation has multiple roles in plant cells, including catabolism of straight-chain fatty acids derived from storage and membrane lipids, catabolism of branched-chain amino acids, and synthesis of indole-3-acetic acid and jasmonic acid (JA) (reviewed in Baker et al, 2006; Graham, 2008). Cts, acx acx, and kat mutant seeds are defective in seedling establishment as they are unable to catabolize fatty acids derived from storage oil and require exogenous sucrose as an alternate carbon source to fuel growth until the mutant seedlings become photoautotrophic (Hayashi et al, 1998, 2002; Germain et al, 2001; Zolman et al, 2001; Footitt et al, 2002; Adham et al, 2005; Pinfield-Wells et al, 2005) These same mutants are severely compromised in germination potential, and this phenotype cannot be rescued by exogenous sucrose (Russell et al, 2000; Footitt et al, 2002, 2006; PinfieldWells et al, 2005). Nicking of the seed coat or removal of the endosperm or testa does overcome the germination block imposed on the embryo in these mutants, which demonstrates that the embryos

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