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Plant Biotechnol J. 2018 Oct;16(10):1778-1787. doi: 10.1111/pbi.12914. Epub 2018 Apr 6.

The rice terpene synthase gene OsTPS19 functions as an (S)-limonene synthase in planta, and its overexpression leads to enhanced resistance to the blast fungus Magnaporthe oryzae.

Author information

1
Key Laboratory of Plant Pathology, Department of Plant Pathology, China Agricultural University, Beijing, China.
2
Department of Plant Sciences, University of Tennessee, Knoxville, TN, USA.
3
Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX, USA.
4
Max Planck Institute for Chemical Ecology, Jena, Germany.
5
State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China.
6
Tea Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou, China.
7
Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN, USA.

Abstract

Rice blast disease, caused by the fungus Magnaporthe oryzae, is the most devastating disease of rice. In our ongoing characterization of the defence mechanisms of rice plants against M. oryzae, a terpene synthase gene OsTPS19 was identified as a candidate defence gene. Here, we report the functional characterization of OsTPS19, which is up-regulated by M. oryzae infection. Overexpression of OsTPS19 in rice plants enhanced resistance against M. oryzae, while OsTPS19 RNAi lines were more susceptible to the pathogen. Metabolic analysis revealed that the production of a monoterpene (S)-limonene was increased and decreased in OsTPS19 overexpression and RNAi lines, respectively, suggesting that OsTPS19 functions as a limonene synthase in planta. This notion was further supported by in vitro enzyme assays with recombinant OsTPS19, in which OsTPS19 had both sesquiterpene activity and monoterpene synthase activity, with limonene as a major product. Furthermore, in a subcellular localization experiment, OsTPS19 was localized in plastids. OsTPS19 has a highly homologous paralog, OsTPS20, which likely resulted from a recent gene duplication event. We found that the variation in OsTPS19 and OsTPS20 enzyme activities was determined by a single amino acid in the active site cavity. The expression of OsTPS20 was not affected by M. oryzae infection. This indicates functional divergence of OsTPS19 and OsTPS20. Lastly, (S)-limonene inhibited the germination of M. oryzae spores in vitro. OsTPS19 was determined to function as an (S)-limonene synthase in rice and plays a role in defence against M. oryzae, at least partly, by inhibiting spore germination.

KEYWORDS:

Oryza sativa ; disease resistance; limonene synthase

PMID:
29509987
PMCID:
PMC6131416
DOI:
10.1111/pbi.12914
[Indexed for MEDLINE]
Free PMC Article

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