Departamento de Genética y Microbiología, Área de Genética (Unidad Asociada al IQFR-CSIC), Facultad de Biología, Universidad de Murcia, Murcia, 30100, Spain.
Instituto de Química Física "Rocasolano", Consejo Superior de Investigaciones Científicas, Madrid, 28006, Spain.
Environ Microbiol. 2022 Apr;24(4):1865-1886. doi: 10.1111/1462-2920.15895. Epub 2022 Jan 27.
Light-induced carotenogenesis in Myxococcus xanthus is controlled by the B -based CarH repressor and photoreceptor, and by a separate intricate pathway involving singlet oxygen, the B -independent CarH paralogue CarA and various other proteins, some eukaryotic-like. Whether other myxobacteria conserve these pathways and undergo photoregulated carotenogenesis is unknown. Here, comparative analyses across 27 Myxococcales genomes identified carotenogenic genes, albeit arranged differently, with carH often in their genomic vicinity, in all three Myxococcales suborders. However, CarA and its associated factors were found exclusively in suborder Cystobacterineae, with carA-carH invariably in tandem in a syntenic carotenogenic operon, except for Cystobacter/Melittangium, which lack CarA but retain all other factors. We experimentally show B -mediated photoregulated carotenogenesis in representative myxobacteria, and a remarkably plastic CarH operator design and DNA binding across Myxococcales. Unlike the two characterized CarH from other phyla, which are tetrameric, Cystobacter CarH (the first myxobacterial homologue amenable to analysis in vitro) is a dimer that combines direct CarH-like B -based photoregulation with CarA-like DNA binding and inhibition by an antirepressor. This study provides new molecular insights into B -dependent photoreceptors. It further establishes the B -dependent pathway for photoregulated carotenogenesis as broadly prevalent across myxobacteria and its evolution, exclusively in one suborder, into a parallel complex B -independent circuit.
粘细菌中的光诱导类胡萝卜素生物合成受 B 型 CarH 阻遏物和光受体、单线态氧、独立于 B 的 CarH 同源物 CarA 和其他各种蛋白（有些类似真核生物）的单独复杂途径控制。其他粘细菌是否保留这些途径并经历光调控的类胡萝卜素生物合成尚不清楚。在这里，通过对 27 个粘细菌目基因组的比较分析，在所有三个粘细菌目亚目中都发现了类胡萝卜素生物合成基因，尽管排列方式不同，但 carH 通常在其基因组附近。然而，CarA 及其相关因子仅存在于 Cystobacterineae 亚目中，除了 Cystobacter/Melittangium 之外，carA-carH 总是在串联的类胡萝卜素生物合成操纵子中，Cystobacter/Melittangium 缺乏 CarA，但保留了所有其他因子。我们通过实验在代表性粘细菌中展示了 B 介导的光调控类胡萝卜素生物合成，以及 across Myxococcales 中非常灵活的 CarH 操纵子设计和 DNA 结合。与来自其他门的两种已表征的 CarH 不同，它们是四聚体，Cystobacter CarH（第一个可在体外进行分析的粘细菌同源物）是一种二聚体，它将直接的 CarH 样 B 型光调控与 CarA 样 DNA 结合以及抗阻遏物的抑制作用结合在一起。这项研究为 B 型依赖性光受体提供了新的分子见解。它进一步确立了光调控类胡萝卜素生物合成的 B 型依赖性途径在粘细菌中的广泛存在，以及其在一个亚目中的进化，成为一个平行的复杂的独立于 B 的途径。
