Rice terpene synthase 20 (OsTPS20) plays an important role in producing terpene volatiles in response to abiotic stresses

Abstract

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, α-terpinene, β-ocimene, γ-terpinene, and α-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 γ-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.

Physiological and molecular analysis of OsTPS30 by gamma irradiation

“…1A). These observations were consistent with previously reported RT-PCR results (Lee et al 2015). Moreover, the OsNAC10 expression was increased with increasing intensity of gamma-rays ( Fig.…”

“…Several aspects regarding the genetic basis of plant-responses to ionizing radiation remain unknown. Lee et al (2015) reported that the expression levels of five OsTPS genes (i.e., OsTPS19, OsTPS20, OsTPS25, OsTPS26, and OsTPS30) are induced by gamma irradiation. However, OsTPS30 was not functionally characterized.…”

“…(Sun et al 2017). Additionally, a previous study revealed that the gamma irradiation of rice seedlings upregulated the expression of OsTPS19, OsTPS20, OsTPS25, OsTPS26, and OsTPS30, although the effect on OsTPS30 was inconclusive (Lee et al 2015). In this study, we analyzed molecular and physiological function of OsTPS30 by gamma irradiation.…”

“…The most studied TPS gene family has been that of Arabidopsis thaliana (Sun et al 1994;Yamaguchi et al 1998;Bohlmann et al 2000;Chen et al 2003;Fäldt et al 2003;Chen et al 2004;Tholl et al 2005;Herde et al 2008), with only a few TPSs having been isolated in cultivated plants, including rice (Oryza sativa), tomato (Solanum lycopersicum), grape (Vitis vinifera), poplar (Populus trichocarpa), and sorghum (Sorghum bicolor) (Falara et al 2011;Irmisch et al 2014;Lee et al 2015;Yoshitomi et al 2016;Zhang et al 2016). However, a detailed analysis of the presence and role of terpenes in these plants has not been published.…”

“…OsTPS19 acts as an (S)-lemonine synthetase in rice and defends against Magnaporthe oryzae by inhibiting spore germination (Chen et al 2018). OsTPS20 plays a major role in producing terpene volatiles during abiotic stress (Lee et al 2015). OsTPS46 plays an important role in rice defense against Rhopalosiphum padi.…”