Wounding stimulates ALLENE OXIDE SYNTHASE gene and increases the level of jasmonic acid in Ipomoea nil cotyledons

Emilia Wilmowicz,Agata Kućko,Katarzyna Panek,Barbara Zabrocka-Nowakowska,Kamil Frankowski,Jan Kopcewicz

doi:10.5586/asbp.3491

Abstract

Allene oxide synthase (AOS) encodes the first enzyme in the lipoxygenase pathway, which is responsible for jasmonic acid (JA) formation. In this study we report the molecular cloning and characterization of InAOS from Ipomoea nil. The full-length gene is composed of 1662 bp and encodes for 519 amino acids. The predicted InAOS contains PLN02648 motif, which is evolutionarily conserved and characteristic for functional enzymatic proteins. We have shown that wounding led to a strong stimulation of the examined gene activity in cotyledons and an increase in JA level, which suggest that this compound may be a modulator of stress responses in I. nil.

Highlights

The biosynthesis of jasmonates (JAs) is initiated by lipoxygenase (LOX) or α-dioxygenase (DOX), which catalyze the formation of hydroperoxides 13(S)-hydroperoxy-octadecatrienoic acid (13-HPOT) and 11(S)-hydroperoxy-hexadecatrienoic acid (11-HPHT), respectively [1]
Maintenance of a jasmonic acid (JA) level appropriate for the control of various processes is possible by multilevel regulation of their biosynthesis, in which a key role is played by, inter alia, LOX, allene oxide synthases (AOS), 0 10 20 30 40 50 60
The InAOS gene encodes for a protein similar to that of allene oxide synthases identified in other plant species [4,5,10]

Summary

Introduction

The biosynthesis of jasmonates (JAs) is initiated by lipoxygenase (LOX) or α-dioxygenase (DOX), which catalyze the formation of hydroperoxides 13(S)-hydroperoxy-octadecatrienoic acid (13-HPOT) and 11(S)-hydroperoxy-hexadecatrienoic acid (11-HPHT), respectively [1]. The committed step of JA biosynthesis is catalyzed by allene oxide synthases (AOS), an atypical family of cytochrome P450, designated CYP74 They use preoxygenated fatty acid hydroperoxide substrates both as oxygen donor and as a source for reducing equivalents. Dehydration of 13-HPOT by AOS results in the formation of unstable short-lived allene oxide intermediates 12,13(S)epoxy-octadecatrienoic acid [12,13(S)-EOT] and 10,11(S)-epoxy-octadecatrienoic acid [10,11(S)-EHT], which are converted by allene oxide cyclase (AOC) to the cyclopentanone ring-containing 12-oxophytodienoic acid (OPDA) or dinor-OPDA (dnOPDA), respectively. Both OPDA and dinor-OPDA undergo three cycles of β-oxidation in the peroxisomes, to generate JA [1,2]. The AOS mRNA level depends on both internal and external factors such as phytohormones, pest attack and wounding

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Conclusion