Nagel, Raimund Bieber, John E. Schmidt-Dannert, Mark G. Nett, Ryan S. Peters, Reuben J. Data_Sheet_2_A Third Class: Functional Gibberellin Biosynthetic Operon in Beta-Proteobacteria.xlsx <p>The ability of plant-associated microbes to produce gibberellin A (GA) phytohormones was first described for the fungal rice pathogen Gibberella fujikuroi in the 1930s. Recently the capacity to produce GAs was shown for several bacteria, including symbiotic alpha-proteobacteria (α-rhizobia) and gamma-proteobacteria phytopathogens. All necessary enzymes for GA production are encoded by a conserved operon, which appears to have undergone horizontal transfer between and within these two phylogenetic classes of bacteria. Here the operon was shown to be present and functional in a third class, the beta-proteobacteria, where it is found in several symbionts (β-rhizobia). Conservation of function was examined by biochemical characterization of the enzymes encoded by the operon from Paraburkholderia mimosarum LMG 23256<sup>T</sup>. Despite the in-frame gene fusion between the short-chain alcohol dehydrogenase/reductase and ferredoxin, the encoded enzymes exhibited the expected activity. Intriguingly, together these can only produce GA<sub>9</sub>, the immediate precursor to the bioactive GA<sub>4</sub>, as the cytochrome P450 (CYP115) that catalyzes the final hydroxylation reaction is missing, similar to most α-rhizobia. However, phylogenetic analysis indicates that the operon from β-rhizobia is more closely related to examples from gamma-proteobacteria, which almost invariably have CYP115 and, hence, can produce bioactive GA<sub>4</sub>. This indicates not only that β-rhizobia acquired the operon by horizontal gene transfer from gamma-proteobacteria, rather than α-rhizobia, but also that they independently lost CYP115 in parallel to the α-rhizobia, further hinting at the possibility of detrimental effects for the production of bioactive GA<sub>4</sub> by these symbionts.</p> symbiosis;gibberellin;rhizobia;legume (nodules);evolution 2018-11-27
    https://frontiersin.figshare.com/articles/dataset/Data_Sheet_2_A_Third_Class_Functional_Gibberellin_Biosynthetic_Operon_in_Beta-Proteobacteria_xlsx/7388015
10.3389/fmicb.2018.02916.s002