Both Allene Oxide Synthases Genes Are Involved in the Biosynthesis of Herbivore-Induced Jasmonic Acid and Herbivore Resistance in Rice.

Jiamei Zeng,Tongfang Zhang,Ran Li,Yonggen Lou,Jiayi Huangfu

doi:10.3390/plants10030442

Jiamei Zeng, Tongfang Zhang + Show 3 more

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https://doi.org/10.3390/plants10030442

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Abstract

Allene oxide synthase (AOS) is the second enzyme in the biosynthesis of the plant defensive hormone jasmonic acid (JA). In rice, there are two AOSs, OsAOS1 and OsAOS2. However, the role of these two AOS genes in herbivore-induced defenses in rice remains unidentified. We cloned the two rice AOS genes and observed that the transcript level of both OsAOS1 and OsAOS2 was enhanced by mechanical wounding, the infestation of the striped stem borer (SSB) (Chilo suppressalis) or brown planthopper (BPH) (Niaparvata lugens), and treatment with JA; however, OsAOS1 responded more rapidly to SSB infestation and JA treatment than did OsAOS2. The antisense expression of OsAOS1 (as-aos1) or OsAOS2 (as-aos2) decreased levels of SSB- or BPH-induced JA, which, in turn, reduced the production of SSB-induced trypsin protease inhibitor (TrypPI) and volatiles as well as the resistance of rice to SSB. In contrast, BPH preferred to feed and oviposit on wild-type (WT) plants over as-aos1 and as-aos2 plants. Moreover, the survival of BPH nymphs on as-aos1 or as-aos2 lines was significantly lower than on WT plants. The increased resistance of as-aos1 or as-aos2 plants to BPH correlated with higher levels of BPH-induced H2O2 and SA. These results indicate that OsAOS1 and OsAOS2 are both involved in herbivore-induced JA biosynthesis and play a vital role in determining the resistance of rice to chewing and phloem-feeding herbivores.

Highlights

When infested by herbivorous insects, plants recognize herbivore-associated molecular patterns and initiate defense-related signaling pathways; these activated pathways, induce the expression of defensive genes and the biosynthesis of defensive compounds, which, in turn, enhance the resistance of plants to herbivorous insects [1,2]
The 13-HPOT is oxidized by an allene oxide synthase (AOS) to form an unstable epoxide, which is cyclized to the 12-oxo phytodienoic acid (12-OPDA) by an allene oxide cyclase (AOC)
Genes increased with different patterns (Figure 1a–f): generally, OsAOS1 responded to these treatments more strongly than did OsAOS2; striped stem borer (SSB) infestation and jasmonic acid (JA) treatment induced the expression of OsAOS2 slowly (≥4 h after treatment) but induced OsAOS1 quickly

Summary

Introduction

When infested by herbivorous insects, plants recognize herbivore-associated molecular patterns and initiate defense-related signaling pathways; these activated pathways, induce the expression of defensive genes and the biosynthesis of defensive compounds, which, in turn, enhance the resistance of plants to herbivorous insects [1,2]. In these signaling pathways, the jasmonates-mediated pathway plays a central role [3,4,5]. It is clear that the enzyme AOS is a regulatory point in the biosynthesis of jasmonates [8,9], which play vital roles in plant development and responses to abiotic and biotic stresses [10]

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