Jasmonic acid is involved in the signaling pathway for fungal endophyte-induced volatile oil accumulation of Atractylodes lancea plantlets.

Chuan-Chao Dai,Cheng-Gang Ren

doi:10.1186/1471-2229-12-128

Abstract

BackgroundJasmonic acid (JA) is a well-characterized signaling molecule in plant defense responses. However, its relationships with other signal molecules in secondary metabolite production induced by endophytic fungus are largely unknown. Atractylodes lancea (Asteraceae) is a traditional Chinese medicinal plant that produces antimicrobial volatiles oils. We incubated plantlets of A. lancea with the fungus Gilmaniella sp. AL12. to research how JA interacted with other signal molecules in volatile oil production.ResultsFungal inoculation increased JA generation and volatile oil accumulation. To investigate whether JA is required for volatile oil production, plantlets were treated with JA inhibitors ibuprofen (IBU) and nordihydroguaiaretic acid. The inhibitors suppressed both JA and volatile oil production, but fungal inoculation could still induce volatile oils. Plantlets were further treated with the nitric oxide (NO)-specific scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide potassium salt (cPTIO), the H2O2 inhibitors diphenylene iodonium (DPI) and catalase (CAT), and the salicylic acid (SA) biosynthesis inhibitors paclobutrazol and 2-aminoindan-2-phosphonic acid. With fungal inoculation, IBU did not inhibit NO production, and JA generation was significantly suppressed by cPTIO, showing that JA may act as a downstream signal of the NO pathway. Exogenous H2O2 could reverse the inhibitory effects of cPTIO on JA generation, indicating that NO mediates JA induction by the fungus through H2O2-dependent pathways. With fungal inoculation, the H2O2 scavenger DPI/CAT could inhibit JA generation, but IBU could not inhibit H2O2 production, implying that H2O2 directly mediated JA generation. Finally, JA generation was enhanced when SA production was suppressed, and vice versa.ConclusionsJasmonic acid acts as a downstream signaling molecule in NO- and H2O2-mediated volatile oil accumulation induced by endophytic fungus and has a complementary interaction with the SA signaling pathway.

Highlights

Jasmonic acid (JA) is a well-characterized signaling molecule in plant defense responses
We report that JA acts as a downstream signal of nitric oxide (NO)- and hydrogen peroxide (H2O2)mediated volatile oil accumulation in A. lancea plantlets induced by endophytic fungus Gilmaniella sp
To investigate whether JA was involved in the fungus-induced volatile oil accumulation, IBU and nordihydroguaiaretic acid (NDGA) were applied; as shown in Figure 1B, both inhibitors suppressed the fungus-induced JA generation, and the fungus-triggered volatile oil production

Summary

Introduction

Jasmonic acid (JA) is a well-characterized signaling molecule in plant defense responses. Its relationships with other signal molecules in secondary metabolite production induced by endophytic fungus are largely unknown. Atractylodes lancea (Asteraceae) is a traditional Chinese medicinal plant that produces antimicrobial volatiles oils. To research how JA interacted with other signal molecules in volatile oil production. Volatile oils from A. lancea show antimicrobial activities as well These oils comprise active secondary metabolites, including the characteristic components atractylone, βeudesmol, hinesol, and atractylodin [3]. Secondary metabolites, such as terpenes, flavonoids, and alkaloids, are believed to be involved in plant responses to many biotic. How endophytic fungus-host interactions affect the accumulation of plant secondary metabolites is an intriguing issue

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