Role of adenosine kinase in the control of Streptomyces differentiations: Loss of adenosine kinase suppresses sporulation and actinorhodin biosynthesis while inducing hyperproduction of undecylprodigiosin in Streptomyces lividans.

Adenosine kinase (ADK) catalyses phosphorylation of adenosine (Ado) and generates adenosine monophosphate (AMP). ADK gene (adk(Sli), an ortholog of SCO2158) was disrupted in Streptomyces lividans by single crossover-mediated vector integration. The adk(Sli) disruption mutant (Deltaadk(Sli)) was devoid of sporulation and a plasmid copy of adk(Sli) restored sporulation ability in Deltaadk(Sli), thus indicating that loss of adk(Sli) abolishes sporulation in S. lividans. Ado supplementation strongly suppressed sporulation ability in S. lividans wild-type (wt), supporting that disruption of adk(Sli) resulted in Ado accumulation, which in turn suppressed sporulation. Cell-free experiments demonstrated that Deltaadk(Sli) lacked ADK activity and in vitro characterization confirms that adk(Sli) encodes ADK. The intracellular level of Ado was highly elevated while the AMP level was significantly reduced after loss of adk(Sli) while Deltaadk(Sli) displayed no significant derivation from wt in the levels of S-adenosylhomocysteine (SAH) and S-adenosylmethionine (SAM). Notably, Ado supplementation to wt lowered AMP content, albeit not to the level of Deltaadk(Sli), implying that the reduction of AMP level is partially forced by Ado accumulation in Deltaadk(Sli). In Deltaadk(Sli), actinorhodin (ACT) production was suppressed and undecylprodigiosin (RED) production was dramatically enhanced; however, Ado supplementation failed to exert this differential control. A promoter-probe assay verified repression of actII-orf4 and induction of redD in Deltaadk(Sli), substantiating that unknown metabolic shift(s) of ADK-deficiency evokes differential genetic control on secondary metabolism in S. lividans. The present study is the first report revealing the suppressive role of Ado in Streptomyces development and the differential regulatory function of ADK activity in Streptomyces secondary metabolism, although the underlying mechanism has yet to be elucidated.