National Key Laboratory of Crop Genetic Improvement and National Center of Plant Gene Research (Wuhan), Huazhong Agricultural University, Wuhan, China.
College of Tropical Crops, Hainan University, Haikou, China.
Nat Plants. 2020 Dec;6(12):1447-1454. doi: 10.1038/s41477-020-00816-7. Epub 2020 Dec 7.
Diterpenoids are the major group of antimicrobial phytoalexins in rice. Here, we report the discovery of a rice diterpenoid gene cluster on chromosome 7 (DGC7) encoding the entire biosynthetic pathway to 5,10-diketo-casbene, a member of the monocyclic casbene-derived diterpenoids. We revealed that DGC7 is regulated directly by JMJ705 through methyl jasmonate-mediated epigenetic control. Functional characterization of pathway genes revealed OsCYP71Z21 to encode a casbene C10 oxidase, sought after for the biosynthesis of an array of medicinally important diterpenoids. We further show that DGC7 arose relatively recently in the Oryza genus, and that it was partly formed in Oryza rufipogon and positively selected for in japonica during domestication. Casbene-synthesizing enzymes that are functionally equivalent to OsTPS28 are present in several species of Euphorbiaceae but gene tree analysis shows that these and other casbene-modifying enzymes have evolved independently. As such, combining casbene-modifying enzymes from these different families of plants may prove effective in producing a diverse array of bioactive diterpenoid natural products.
二萜类化合物是水稻中主要的抗菌植物抗毒素。在这里，我们报告了在水稻第 7 号染色体上发现了一个二萜类化合物基因簇（DGC7），它编码了 5,10-二酮-贝壳杉烯的全生物合成途径，5,10-二酮-贝壳杉烯是单环贝壳杉烯衍生的二萜类化合物的一员。我们揭示了 DGC7 通过茉莉酸甲酯介导的表观遗传控制直接受到 JMJ705 的调控。途径基因的功能表征表明，OsCYP71Z21 编码贝壳杉烯 C10 氧化酶，该酶是合成一系列具有药用价值的二萜类化合物的关键酶。我们进一步表明，DGC7 在稻属中相对较新出现，并且在驯化过程中，它在红稻中部分形成，并在粳稻中受到正选择。具有与 OsTPS28 功能等效的贝壳杉烯合成酶存在于几种大戟科植物中，但基因树分析表明，这些和其他贝壳杉烯修饰酶已经独立进化。因此，将来自这些不同植物科的贝壳杉烯修饰酶结合起来，可能有助于生产出多种多样的生物活性二萜类天然产物。
