Characterization of diterpene synthase genes in the wild rice species Oryza brachyatha provides evolutionary insight into rice phytoalexin biosynthesis
- Faculty of Agriculture, Yamagata University, Tsuruoka, 997-8555 (Japan)
- Department of Biosciences, Teikyo University, Utsunomiya, 320-8551 (Japan)
- Plant Genetics Laboratory, National Institute of Genetics, Shizuoka, 411-8540 (Japan)
- Biotechnology Research Center, The University of Tokyo, Bunkyo-ku, 113-8657 (Japan)
Highlights: • Diterpene-type phtyoalexin oryzalexins are only found in Oryza sativa. • Copalyl diphosphate synthase (CPS) and kaurene synthase-like in turn make diterpenes. • A distant wild rice species O. brachyantha has different CPS activity to O. sativa. • CPS activity type determines the range of diterpene-type phytoalexins produced. • syn-CPS acquisition was necessary for evolution of oryzalexin S production in rice. Cultivated rice (Oryza sativa; Os) produces a variety of labdane-related diterpenoids; not only phytohormone gibberellins (GAs) but also phytoalexins for defense including phytocassanes, momilactones and oryzalexins. Their carbon skeleton diterpenes are constructed from geranylgeranyl diphosphate via ent-copalyl diphosphate (ent-CDP) or its diastereomer syn-CDP. These two-step reactions are successively catalyzed by homologs of the two diterpene synthases, ent-CDP synthase (ent-CPS) and ent-kaurene synthase (KS) that are responsible for the biosynthesis of GAs; e.g. OsCPS4 and OsKSL8 that are involved in the biosynthesis of oryzalexin S, a rice phytoalexin. Oryza brachyantha (Ob) is the most distant wild rice species from Os among the Oryza genus. We previously reported that the Ob genome contains ObCPS{sub 1}1g, ObKSL8-a, ObKSL8-b and ObKSL8-c for specialized metabolism at a locus similar to the OsKSL8 locus on chromosome 11. These Ob genes are closely related to OsCPS4 and OsKSL8, respectively. We herein characterize the diterpene synthase genes in Ob, using functional analyses and expression analysis. Recombinant OsKSL8 and ObKSL8-a showed the same in vitro function when syn-CDP or normal-CDP were used as substrates. Nonetheless, our results suggest that Ob produces normal-CDP-related diterpenoid phytoalexins, presumably via ObKSL8-a, while Os produces a syn-CDP-related phytoalexin, oryzalexin S, via OsKSL8. This difference must be due to the kinds of CPS that are present in each species; Os has OsCPS4 encoding syn-CPS, while Ob has ObCPS{sub 1}1g encoding normal-CPS. Thus, we propose the evolutionary history underlying oryzalexin S biosynthesis: the gain of a syn-CPS was a critical event allowing the biosynthesis of oryzalexin S.
- OSTI ID:
- 23134350
- Journal Information:
- Biochemical and Biophysical Research Communications, Vol. 503, Issue 3; Other Information: Copyright (c) 2018 Elsevier Inc. All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0006-291X
- Country of Publication:
- United States
- Language:
- English
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