Cyclic di-AMP metabolism and functions in Streptomyces

革兰氏阳性土壤细菌链菌属于自然界最有能力的天然产物工厂，是各种抗生素和其他生物活性分子的重要来源，用于医疗，兽医和农业用途。这些次生代谢物的产生在时间上和遗传上与一个复杂的发育生命周期相协调，包括作为分枝菌丝的营养菌丝生长和通过在称为气生菌丝的特殊生殖结构上形成的孢子扩散。我们最近的研究表明，在委内瑞拉链霉菌中，含有二腺苷酸环化酶（DAC）结构域的蛋白DisA产生核苷酸第二信使环二amp，通过与RpfA基因5-未翻译先导区（UTR）的核开关结合，控制细胞壁裂解酶RpfA的水平。然而，我们对c-di-AMP在链霉菌生理中的生物合成、转换和功能的了解仍然非常有限。在SPP 1879中提出的工作的目的是分析和表征DisA和c-di-AMP在委内瑞拉的分子细节的作用。我们将确定的条件DisA表达活跃和定义这种蛋白质如何c-di-AMP有助于分化和压力的生存策略是否受雇于链霉菌属spp。因为不含任何的特征已经c-di-AMP-binding蛋白质,我们将执行一个全球屏幕c-di-AMP效应蛋白,这将使我们能够确定一个潜在的新型c-di-AMP-degrading磷酸二酯酶和效果器的一个新类。此外，在我们以前未发表的研究中，我们发现委内瑞拉S.产生一种到目前为止尚未表征的环二核苷酸。对这种化合物的详细分析和表征将导致在细菌中发现一种新型的基于核苷酸的第二信使。总之，这项工作将大大提高我们对链霉菌的生理和应激生存机制的理解，并有助于更好地了解c-di-AMP信号在多细胞分化和次生代谢物产生的新生理背景下的作用。

The Gram-positive soil bacteria streptomycetes belong to natures most competent natural product factories and are an important source of diverse antibiotics and other bioactive molecules for medical, veterinary and agricultural use. The production of these secondary metabolites is temporally and genetically coordinated with a complex developmental life cycle involving growth as vegetative mycelium of branching hyphae and dispersion via spores formed on specialized reproductive structures called aerial hyphae. We have recently shown that in Streptomyces venezuelae the diadenylate cyclase (DAC) domain-containing protein DisA produces the nucleotide second messenger cyclic di-AMP which controls the levels of the cell wall lytic enzyme RpfA by binding to a riboswitch in the 5-untranslated leader region (UTR) of the rpfA gene. However, our knowledge about the biosynthesis, turnover and functions of c-di-AMP in the physiology of streptomycetes is still very limited. The aim of the proposed work within the SPP 1879 is to analyse and characterise in molecular detail the roles of DisA and c-di-AMP in S. venezuelae. We will determine the conditions under which DisA is expressed and active and define how this protein and c-di-AMP contribute to differentiation and stress survival strategies employed by Streptomyces spp. Since streptomycetes do not contain any of the already characterised c-di-AMP-binding proteins, we will perform a global screen for c-di-AMP effector proteins, which will allow us to identify a potentially novel type of c-di-AMP-degrading phosphodiesterases and a new class of effectors. Further, in our previous, unpublished studies we found, that S. venezuelae produces an up to now uncharacterised cyclic di-nucleotide. Detailed analysis and characterisation of this compound will lead to the discovery of a novel type of nucleotide-based second messengers in bacteria. Altogether, this work will greatly improve our understanding of the physiology and stress survival mechanisms in Streptomyces spp. and contribute to a better knowledge of c-di-AMP signalling in a new physiological context involving multicellular differentiation and secondary metabolite production.