Rice contains a biosynthetic gene cluster associated with production of the casbane‐type diterpenoid phytoalexin ent‐10‐oxodepressin

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Liang, Jin
Shen, Qinqin
Peters, Reuben
Wang, Liping
Liu, Jiang
Fu, Jingye
Zhao, Le
Xu, Meimei
Peters, Reuben
Wang, Qiang
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• Diterpenoids play important roles in rice microbial disease resistance as phytoalexins, as well as acting in allelopathy and abiotic stress responses. Recently, the casbane-type phytoalexin ent-10- oxodepressin was identified in rice, but its biosynthesis has not yet been elucidated.

• Here ent-10-oxodepressin biosynthesis was investigated via co-expression analysis and biochemical characterization, with use of the CRISPR/Cas9 technology for genetic analysis.

• The results identified a biosynthetic gene cluster (BGC) on rice chromosome 7 (c7BGC), containing the relevant ent-casbene synthase (OsECBS), and four cytochrome P450 (CYP) genes from the CYP71Z subfamily. Three of these CYPs were shown to act on ent-casbene, with CYP71Z2 able to produce a keto group at carbon-5 (C5), while the closely related paralogs CYP71Z21 and CYP71Z22 both readily produce a keto group at C10. Together these C5 and C10 oxidases can elaborate ent-casbene to ent-10-oxodepressin (5,10-diketo-ent-casbene). OsECBS knock-out lines no longer produce casbane-type diterpenoids and exhibit impaired resistance to the rice fungal blast pathogen Magnaporthe oryzae.

• Elucidation of ent-10-oxodepressin biosynthesis and the associated c7BGC provides not only a potential target for molecular breeding, but also, given the intriguing parallels to the independently assembled BGCs for casbene-derived diterpenoids in the Euphorbiaceae, further insight into plant BGC evolution, as discussed here.

<p>This is the peer reviewed version of the following article: Liang, Jin, Qinqin Shen, Liping Wang, Jiang Liu, Jingye Fu, Zhao Le, Meimei Xu, Reuben J. Peters, and Qiang Wang. "Rice contains a biosynthetic gene cluster associated with production of the casbane‐type diterpenoid phytoalexin ent‐10‐oxodepressin." <em>New Phytologist</em> (2021), which has been published in final form at doi:<a href="https://doi.org/10.1111/nph.17406">10.1111/nph.17406</a>. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.</p>
rice, phytoalexins, casbene, biosynthesis, disease resistance, gene cluster