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1. ¹⁸ O ₂ labeling experiments illuminate the oxidation of ent-kaurene in bacterial gibberellin biosynthesis

   https://doi.org/10.1039/c7ob01819c  

   Nagel, Raimund; Peters, Reuben J. (January 2017, Org. Biomol. Chem.)

   Bacteria can produce gibberellin plant hormones. While the bacterial biosynthetic pathway is similar to that of plants, the individual enzymes are very distantly related and arose via convergent evolution. The cytochromes P450 (CYPs) that catalyze the multi-step oxidation of the alkane precursor ent -kaurene ( 1 ) to ent -kauren-19-oic acid ( 5 ), are called ent -kaurene oxidases (KOs), and in plants are from the CYP701 family, and share less than 19% amino acid sequence identity with those from bacteria, which are from the phylogenetically distinct CYP117 family. Here the reaction series catalyzed by CYP117 was examined by 18 O 2 labeling experiments, the results indicate successive hydroxylation of 1 to ent -kauren-19-ol ( 2 ) and then ent -kauren-19,19-diol ( 3 ) and most likely an intervening dehydration to ent -kauren-19-al ( 4 ) prior to the concluding hydroxylation to 5 . Accordingly, the bacterial and plant KOs converged on catalysis of the same series of reactions, despite their independent evolutionary origin. 

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2. Gibberellin dynamics governing nodulation revealed using GIBBERELLIN PERCEPTION SENSOR 2 in Medicago truncatula lateral organs

   https://doi.org/10.1093/plcell/koae201  

   Drapek, Colleen; Rizza, Annalisa; Mohd-Radzman, Nadiatul A; Schiessl, Katharina; Dos_Santos_Barbosa, Fabio; Wen, Jiangqi; Oldroyd, Giles_E D; Jones, Alexander M (July 2024, The Plant Cell)

   Abstract During nutrient scarcity, plants can adapt their developmental strategy to maximize their chance of survival. Such plasticity in development is underpinned by hormonal regulation, which mediates the relationship between environmental cues and developmental outputs. In legumes, endosymbiosis with nitrogen-fixing bacteria (rhizobia) is a key adaptation for supplying the plant with nitrogen in the form of ammonium. Rhizobia are housed in lateral root-derived organs termed nodules that maintain an environment conducive to Nitrogenase in these bacteria. Several phytohormones are important for regulating the formation of nodules, with both positive and negative roles proposed for gibberellin (GA). In this study, we determine the cellular location and function of bioactive GA during nodule organogenesis using a genetically encoded second-generation GA biosensor, GIBBERELLIN PERCEPTION SENSOR 2 in Medicago truncatula. We find endogenous bioactive GA accumulates locally at the site of nodule primordia, increasing dramatically in the cortical cell layers, persisting through cell divisions, and maintaining accumulation in the mature nodule meristem. We show, through misexpression of GA-catabolic enzymes that suppress GA accumulation, that GA acts as a positive regulator of nodule growth and development. Furthermore, increasing or decreasing GA through perturbation of biosynthesis gene expression can increase or decrease the size of nodules, respectively. This is unique from lateral root formation, a developmental program that shares common organogenesis regulators. We link GA to a wider gene regulatory program by showing that nodule-identity genes induce and sustain GA accumulation necessary for proper nodule formation. 

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3. A Role for GIBBERELLIN 2-OXIDASE6 and Gibberellins in Regulating Nectar Production

   https://doi.org/10.1016/j.molp.2015.12.019  

   Wiesen, Lisa B.; Bender, Ricci L.; Paradis, Travis; Larson, Alexie; Perera, M. Ann D.N.; Nikolau, Basil J.; Olszewski, Neil E.; Carter, Clay J. (May 2016, Molecular Plant)
4. Highlights in gibberellin research: A tale of the dwarf and the slender

   https://doi.org/10.1093/plphys/kiae044  

   Shani, Eilon; Hedden, Peter; Sun, Tai-ping (January 2024, Plant Physiology)

   Abstract It has been almost a century since biologically active gibberellin (GA) was isolated. Here, we give a historical overview of the early efforts in establishing the GA biosynthesis and catabolism pathway, characterizing the enzymes for GA metabolism, and elucidating their corresponding genes. We then highlight more recent studies that have identified the GA receptors and early GA signaling components (DELLA repressors and F-box activators), determined the molecular mechanism of DELLA-mediated transcription reprograming, and revealed how DELLAs integrate multiple signaling pathways to regulate plant vegetative and reproductive development in response to internal and external cues. Finally, we discuss the GA transporters and their roles in GA-mediated plant development. 

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5. Labeling Studies Clarify the Committed Step in Bacterial Gibberellin Biosynthesis

   https://doi.org/10.1021/acs.orglett.6b02569  

   Nett, Ryan S.; Dickschat, Jeroen S.; Peters, Reuben J. (December 2016, Organic Letters)