Campus Units

Biochemistry, Biophysics and Molecular Biology, Roy J. Carver Department of

Document Type


Publication Version

Accepted Manuscript

Publication Date


Journal or Book Title

The Plant Journal





First Page


Last Page





Rice (Oryza sativa) produces a variety of labdane-related diterpenoids as phytoalexins and allelochemicals. The production of these important natural products has been partially elucidated. However, the oxidases responsible for production of the keto groups found in many of these diterpenoids have largely remained unknown. Only one short-chain alcohol dehydrogenase/reductases (SDRs), which has been proposed to catalyze the last step in such a pathway, has been characterized to-date. While rice contains >220 SDRs, only the transcription of five has been shown to be induced by the fungal cell wall elicitor chitin. This includes the momilactone A synthase (OsMAS/SDR110C-MS1), with the other four all falling in the same SDR110C family, further suggesting roles in diterpenoid biosynthesis. Here biochemical characterization with simplified substrate analogs was first used to indicate potential functions, which were then supported by further analyses with key biosynthetic intermediates. Kinetic studies were then employed to further clarify these roles. Surprisingly, OsSDR110C-MS2 more efficiently catalyzes the final oxidation to produce momilactone A that was previously assigned to OsMAS/SDR110C-MS1, and we speculate that this latter SDR may have an alternative function instead. On the other hand, two of these SDRs clearly appear to act in oryzalexin biosynthesis, with OsSDR110C-MI3 readily oxidizing the 3α-hydroxyl of oryzalexin D, while OsSDR110C-MS3 can also oxidize the accompanying 7β-hydroxyl. Together, these SDRs then serve to produce oryzalexins A – C from oryzalexin D, essentially completing elucidation of the biosynthesis of this family of rice phytoalexins.


This is the peer reviewed version of the following article: Kitaoka, Naoki, Yisheng Wu, Jiachen Zi, and Reuben J. Peters. "Investigating inducible short‐chain alcohol dehydrogenases/reductases clarifies rice oryzalexin biosynthesis." The plant journal 88, no. 2 (2016): 271-279, which has been published in final form at doi: 10.1111/tpj.13249. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.

Copyright Owner

The Authors. The Plant Journal, John Wiley & Sons Ltd



File Format


Published Version