Journal
PROTOPLASMA
Volume 252, Issue 4, Pages 997-1007Publisher
SPRINGER WIEN
DOI: 10.1007/s00709-014-0735-8
Keywords
Gamma-ray; Hydrogen peroxide; (S)-limonene synthase; Oxidative stress; Terpene volatile; UV-B radiation
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Funding
- Nuclear R & D Program of the Ministry of Science, ICT and Future Planning (MSIP), Republic of Korea
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This study examined the volatile terpenes produced by rice seedlings in response to oxidative stress induced by various abiotic factors. Solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) analyses revealed that when exposed to UV-B radiation, rice seedlings emitted a bouquet of monoterpene mixtures in a time-dependent manner. The mixtures comprised limonene, sabinene, myrcene, alpha-terpinene, beta-ocimene, gamma-terpinene, and alpha-terpinolene. Among them, (S)-limonene was the most abundant volatile, discriminated by chiral SPME-GC-MS. The volatile profiles collected from rice plants treated with both gamma-irradiation and H2O2 were identical to those observed in the UV-B irradiated plants, thus indicating that the volatile mixtures were specifically produced in response to oxidative stress, particularly in the presence of H2O2. Using a reverse genetics approach, we isolated full-length rice terpene synthase 20 (OsTPS20, 599 amino acids, 69.39 kDa), which was further characterized as an (S)-limonene synthase by removing the N-terminal signal peptide (63 amino acids) of the protein. The recombinant OsTPS20 protein catalyzed the conversion of geranyl diphosphate to (S)-limonene and other minor monoterpenes, essentially covering all of the volatile compounds detected from the plant. Moreover, qRT-PCR revealed that the transcript levels of OsTPS20 were significantly induced in response to oxidative stress, thereby suggesting that OsTPS20 plays a major role in producing terpene volatiles during abiotic stress. Detailed biochemical analyses and the unusual domain characteristics of OsTPS20 are also discussed in this report.
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