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1. Mechanistic Insights into the Formation of the 6,10‐Bicyclic Eunicellane Skeleton by the Bacterial Diterpene Synthase Bnd4

   https://doi.org/10.1002/ange.202109641  

   Xu, Baofu ; Tantillo, Dean J. ; Rudolf, Jeffrey D. ( September 2021 , Angewandte Chemie)

   The eunicellane diterpenoids are a unique family of natural products seen in marine organisms, plants, and bacteria. We used a series of biochemical, bioinformatics, and theoretical experiments to investigate the mechanism of the first diterpene synthase known to form the eunicellane skeleton. Deuterium labeling studies and quantum chemical calculations support that Bnd4, fromStreptomycessp. (CL12‐4), forms the 6,10‐bicyclic skeleton through a 1,10‐cyclization, 1,3‐hydride shift, and 1,14‐cyclization cascade. Bnd4 also demonstrated sesquiterpene cyclase activity and the ability to prenylate small molecules. Bnd4 possesses a unique D⁹⁴NxxxD motif and mutation experiments confirmed an absolute requirement for D94 as well as E169.

    

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2. Mechanistic Insights into the Formation of the 6,10‐Bicyclic Eunicellane Skeleton by the Bacterial Diterpene Synthase Bnd4

   https://doi.org/10.1002/anie.202109641  

   Xu, Baofu ; Tantillo, Dean J. ; Rudolf, Jeffrey D. ( September 2021 , Angewandte Chemie International Edition)

   The eunicellane diterpenoids are a unique family of natural products seen in marine organisms, plants, and bacteria. We used a series of biochemical, bioinformatics, and theoretical experiments to investigate the mechanism of the first diterpene synthase known to form the eunicellane skeleton. Deuterium labeling studies and quantum chemical calculations support that Bnd4, fromStreptomycessp. (CL12‐4), forms the 6,10‐bicyclic skeleton through a 1,10‐cyclization, 1,3‐hydride shift, and 1,14‐cyclization cascade. Bnd4 also demonstrated sesquiterpene cyclase activity and the ability to prenylate small molecules. Bnd4 possesses a unique D⁹⁴NxxxD motif and mutation experiments confirmed an absolute requirement for D94 as well as E169.

    

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3. Promiscuous terpene synthases from Prunella vulgaris highlight the importance of substrate and compartment switching in terpene synthase evolution

   https://doi.org/10.1111/nph.15778  

   Johnson, Sean R. ; Bhat, Wajid Waheed ; Sadre, Radin ; Miller, Garret P. ; Garcia, Alekzander Sky ; Hamberger, Björn ( April 2019 , New Phytologist)

   The mint family (Lamiaceae) is well documented as a rich source of terpene natural products. More than 200 diterpene skeletons have been reported from mints, but biosynthetic pathways are known for just a few of these.

   We crossreferenced chemotaxonomic data with publicly available transcriptomes to select common selfheal (Prunella vulgaris) and its highly unusual vulgarisin diterpenoids as a case study for exploring the origins of diterpene skeletal diversity in Lamiaceae. Four terpene synthases (TPS) from the TPS‐a subfamily, including two localised to the plastid, were cloned and functionally characterised. Previous examples of TPS‐a enzymes from Lamiaceae were cytosolic and reported to act on the 15‐carbon farnesyl diphosphate. Plastidial TPS‐a enzymes using the 20‐carbon geranylgeranyl diphosphate are known from other plant families, having apparently arisen independently in each family.

   All four new enzymes were found to be active on multiple prenyl‐diphosphate substrates with different chain lengths and stereochemistries. One of the new enzymes catalysed the cyclisation of geranylgeranyl diphosphate into 11‐hydroxy vulgarisane, the likely biosynthetic precursor of the vulgarisins.

   We uncovered the pathway to a rare diterpene skeleton. Our results support an emerging paradigm of substrate and compartment switching as important aspects of TPS evolution and diversification.

    

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4. Uncovering a miltiradiene biosynthetic gene cluster in the Lamiaceae reveals a dynamic evolutionary trajectory

   https://doi.org/10.1038/s41467-023-35845-1  

   Bryson, Abigail E. ; Lanier, Emily R. ; Lau, Kin H. ; Hamilton, John P. ; Vaillancourt, Brieanne ; Mathieu, Davis ; Yocca, Alan E. ; Miller, Garret P. ; Edger, Patrick P. ; Buell, C. Robin ; et al ( December 2023 , Nature Communications)

   Abstract The spatial organization of genes within plant genomes can drive evolution of specialized metabolic pathways. Terpenoids are important specialized metabolites in plants with diverse adaptive functions that enable environmental interactions. Here, we report the genome assemblies of Prunella vulgaris , Plectranthus barbatus , and Leonotis leonurus . We investigate the origin and subsequent evolution of a diterpenoid biosynthetic gene cluster (BGC) together with other seven species within the Lamiaceae (mint) family. Based on core genes found in the BGCs of all species examined across the Lamiaceae, we predict a simplified version of this cluster evolved in an early Lamiaceae ancestor. The current composition of the extant BGCs highlights the dynamic nature of its evolution. We elucidate the terpene backbones generated by the Callicarpa americana BGC enzymes, including miltiradiene and the terpene (+)-kaurene, and show oxidization activities of BGC cytochrome P450s. Our work reveals the fluid nature of BGC assembly and the importance of genome structure in contributing to the origin of metabolites. 

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5. Unexpected genomic, biosynthetic and species diversity of Streptomyces bacteria from bats in Arizona and New Mexico, USA

   https://doi.org/10.1186/s12864-021-07546-w  

   Park, Cooper J. ; Caimi, Nicole A. ; Buecher, Debbie C. ; Valdez, Ernest W. ; Northup, Diana E. ; Andam, Cheryl P. ( December 2021 , BMC Genomics)

   null (Ed.)

   Abstract Background Antibiotic-producing Streptomyces bacteria are ubiquitous in nature, yet most studies of its diversity have focused on free-living strains inhabiting diverse soil environments and those in symbiotic relationship with invertebrates. Results We studied the draft genomes of 73 Streptomyces isolates sampled from the skin (wing and tail membranes) and fur surfaces of bats collected in Arizona and New Mexico. We uncovered large genomic variation and biosynthetic potential, even among closely related strains. The isolates, which were initially identified as three distinct species based on sequence variation in the 16S rRNA locus, could be distinguished as 41 different species based on genome-wide average nucleotide identity. Of the 32 biosynthetic gene cluster (BGC) classes detected, non-ribosomal peptide synthetases, siderophores, and terpenes were present in all genomes. On average, Streptomyces genomes carried 14 distinct classes of BGCs (range = 9–20). Results also revealed large inter- and intra-species variation in gene content (single nucleotide polymorphisms, accessory genes and singletons) and BGCs, further contributing to the overall genetic diversity present in bat-associated Streptomyces . Finally, we show that genome-wide recombination has partly contributed to the large genomic variation among strains of the same species. Conclusions Our study provides an initial genomic assessment of bat-associated Streptomyces that will be critical to prioritizing those strains with the greatest ability to produce novel antibiotics. It also highlights the need to recognize within-species variation as an important factor in genetic manipulation studies, diversity estimates and drug discovery efforts in Streptomyces . 

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