Prodiginines Postpone the Onset of Sporulation in <i>Streptomyces coelicolor</i>

• Main Authors: Elodie Tenconi, Matthew Traxler, Déborah Tellatin, Gilles P. van Wezel, Sébastien Rigali
• Format: Article
• Language: English
• Published: MDPI AG 2020-11-01
• Series: Antibiotics
• Subjects: programmed cell death; bacterial development; role of antibiotics; cell differentiation; morphogenesis; streptorubin
• Online Access: https://www.mdpi.com/2079-6382/9/12/847

Bioactive natural products are typically secreted by the producer strain. Besides that, this allows the targeting of competitors, also filling a protective role, reducing the chance of self-killing. Surprisingly, DNA-degrading and membrane damaging prodiginines (PdGs) are only produced intracellularly, and are required for the onset of the second round of programmed cell death (PCD) in <i>Streptomyces coelicolor</i>. In this work, we investigated the influence of PdGs on the timing of the morphological differentiation of <i>S. coelicolor</i>. The deletion of the transcriptional activator gene <i>redD</i> that activates the <i>red</i> cluster for PdGs or nutrient-mediated reduction of PdG synthesis both resulted in the precocious appearance of mature spore chains. Transcriptional analysis revealed an accelerated expression of key developmental genes in the <i>redD</i> null mutant, including <i>bldN</i> for the developmental σ factor BldN which is essential for aerial mycelium formation. In contrast, PdG overproduction due to the enhanced copy number of <i>redD</i> resulted in a delay or block in sporulation. In addition, confocal fluorescence microscopy revealed that the earliest aerial hyphae do not produce PdGs. This suggests that filaments that eventually differentiate into spore chains and are hence required for survival of the colony, are excluded from the second round of PCD induced by PdGs. We propose that one of the roles of PdGs would be to delay the entrance of <i>S. coelicolor</i> into the dormancy state (sporulation) by inducing the leakage of the intracellular content of dying filaments thereby providing nutrients for the survivors.