Uncrossing the ‘X’: Characterization of alternative alleles for KSLX in Oryza

The widely cultivated Asian rice (Oryza sativa) produces a variety of physiologically relevant diterpenoid products, which range in effect from the phytohormone gibberellin, derived from ent-kaurene, to phytoalexins such as the momilactones, derived from syn-pimara-7,15-diene. Previous reports have shown functional variation in the kaurene synthase-like (KSL) genes responsible for synthesizing diterpene precursors to more specialized metabolites, leading to the creation of distinct diterpenoids from allelomorphic genes. Here is reported the product of two previously discovered but uncharacterized alleles of the unusual KSLX, representing a cross between (fusion of) the tandem pair KSL8-KSL9p found in most cultivars. The previously characterized allele (KSLXo) was reported to act on syn-copalyl pyrophosphate (syn-CPP) to produce syn-abieta-7,12-diene, precursor to the phytoalexin oryzalactone. However, at least one other functionally distinct allele was reported from the O. sativa pan-genome (KSLXn), along with another phylogenetically distinct allele found in Oryza barthii (KSLXb), but these were not further characterized. Here both KSLXn and KSLXb were found to selectively react with syn-CPP and produce syn-pimara-9(11),15-diene, a novel diterpene in rice. Additionally, evolution of this locus was investigated, with KSLXb hypothesized to be a functional KSL9. The striking complexity of this locus, which includes distinct composition (KSL8-KSL9(p) or KSLX) as well as allelomorphism of both KSL8 and KSLX, suggests it is subject to balancing selection, consistent with the competing pressures exerted on phytoalexin biosynthesis. Regardless, the studies reported here clarify this additional example of allelomorphic variation in the rice KSL family, providing insight into the rice pan-genomic diterpenoid arsenal.

• Publication year

  2025

• Venue

  Phytochemistry

• Publication date

  2025-08-08

• Fields of study

  Biology, Medicine, Environmental Science

• Identifiers
  DOI 10.1016/j.phytochem.2025.114634PMID 40784629PMCID 12401587
• External record

  Open on Semantic Scholar

• Source metadata

  Semantic Scholar, PubMed

• No claims are published for this paper.

• No concepts are published for this paper.

• Discovery of a plant-like tridomain bifunctional syn-abieta-7,13-diene synthase in Streptomyces

  2025cited by this paper
• Between scents and sterols: Cyclization of labdane-related diterpenes as model systems for enzymatic control of carbocation cascades

  2024cited by this paper
• Discovery of bifunctional diterpene cyclases/synthases in bacteria supports a bacterial origin for the plant terpene synthase gene family

  2024influential reference
• Double-barreled defense: dual ent-miltiradiene synthases in most rice cultivars

  2024cited by this paper
• Identification and evolution of a diterpenoid phytoalexin oryzalactone biosynthetic gene in the genus Oryza.

  2024influential reference
• Natural variation of diterpenoid phytoalexins in rice: Aromatic diterpenoid phytoalexins in specific cultivars.

  2023cited by this paper
• Rice Phytoalexins: Half a Century of Amazing Discoveries; Part I: Distribution, Biosynthesis, Chemical Synthesis, and Biological Activities

  2023cited by this paper
• Oryzalexin S biosynthesis: a cross-stitched disappearing pathway

  2023cited by this paper
• Plant (di)terpenoid evolution: from pigments to hormones and beyond

  2022cited by this paper
• Gramene: A Resource for Comparative Analysis of Plants Genomes and Pathways.

  2022cited by this paper
• A super pan-genomic landscape of rice

  2022cited by this paper
• Functional kaurene-synthase-like diterpene synthases lacking a gamma domain are widely present in Oryza and related species.

  2021cited by this paper
• Host–parasite co-evolution and its genomic signature

  2020cited by this paper
• Specialized diterpenoid metabolism in monocot crops: Biosynthesis and chemical diversity.

  2020cited by this paper
• Whole-Genome Sequencing of the NARO World Rice Core Collection (WRC) as the Basis for Diversity and Association Studies

  2020cited by this paper
• Combinatorial biosynthesis and the basis for substrate promiscuity in class I diterpene synthases.

  2019cited by this paper
• RAxML-NG: a fast, scalable and user-friendly tool for maximum likelihood phylogenetic inference

  2018cited by this paper
• Genomes of 13 domesticated and wild rice relatives highlight genetic conservation, turnover and innovation across the genus Oryza

  2018cited by this paper
• Inferring Roles in Defense from Metabolic Allocation of Rice Diterpenoids[OPEN]

  2018cited by this paper
• Characterization of diterpene synthase genes in the wild rice species Oryza brachyatha provides evolutionary insight into rice phytoalexin biosynthesis.

  2018influential reference
• The rice genome revolution: from an ancient grain to Green Super Rice

  2018cited by this paper
• Characterization and evolutionary analysis of ent-kaurene synthase like genes from the wild rice species Oryza rufipogon.

  2016influential reference
• Gramene: A Resource for Comparative Analysis of Plants Genomes and Pathways.

  2016cited by this paper
• To gibberellins and beyond! Surveying the evolution of (di)terpenoid metabolism.

  2014influential reference
• Author Manuscript

  2013cited by this paper
• Evident and latent plasticity across the rice diterpene synthase family with potential implications for the evolution of diterpenoid metabolism in the cereals.

  2011cited by this paper
• Trinuclear metal clusters in catalysis by terpenoid synthases

  2010cited by this paper
• A modular approach for facile biosynthesis of labdane-related diterpenes.

  2007cited by this paper
• Functional characterization of the rice kaurene synthase-like gene family.

  2007cited by this paper
• An unexpected diterpene cyclase from rice: functional identification of a stemodene synthase.

  2006cited by this paper
• Biological functions of ent- and syn-copalyl diphosphate synthases in rice: key enzymes for the branch point of gibberellin and phytoalexin biosynthesis.

  2004influential reference
• Stemar‐13‐ene synthase, a diterpene cyclase involved in the biosynthesis of the phytoalexin oryzalexin S in rice

  2004influential reference
• Identification of Syn-Pimara-7,15-Diene Synthase Reveals Functional Clustering of Terpene Synthases Involved in Rice Phytoalexin/Allelochemical Biosynthesis1

  2004cited by this paper
• Rice Contains Two Disparate ent-Copalyl Diphosphate Synthases with Distinct Metabolic Functions1

  2004cited by this paper
• Diterpene Cyclases Responsible for the Biosynthesis of Phytoalexins, Momilactones A, B, and Oryzalexins A–F in Rice

  2004influential reference
• Functional identification of rice syn-copalyl diphosphate synthase and its role in initiating biosynthesis of diterpenoid phytoalexin/allelopathic natural products.

  2004cited by this paper
• An Overview of Gibberellin Metabolism Enzyme Genes and Their Related Mutants in Rice1[w]

  2004cited by this paper

• No citing papers are available for this paper.