AUTHOR=López-García María T. , Yagüe Paula , González-Quiñónez Nathaly , Rioseras Beatriz , Manteca Angel 

TITLE=The SCO4117 ECF Sigma Factor Pleiotropically Controls Secondary Metabolism and Morphogenesis in Streptomyces coelicolor

JOURNAL=Frontiers in Microbiology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2018.00312

DOI=10.3389/fmicb.2018.00312

ISSN=1664-302X

ABSTRACT=<p>Extracytoplasmic function (ECF) sigma factors are a major type of bacterial signal-transducers whose biological functions remain poorly characterized in streptomycetes. In this work we studied SCO4117, a conserved ECF sigma factor from the ECF52 family overexpressed during substrate and aerial mycelium stages. The ECF52 sigma factors harbor, in addition to the ECF sigma factor domain, a zinc finger domain, a transmembrane region, a proline-rich C-terminal extension, and a carbohydrate-binding domain. This class of ECF sigma factors is exclusive to Actinobacteria. We demonstrate that <italic>SCO4117</italic> is an activator of secondary metabolism, aerial mycelium differentiation, and sporulation, in all the culture media (sucrose-free R5A, GYM, MM, and SFM) analyzed. Aerial mycelium formation and sporulation are delayed in a <italic>SCO4117</italic> knockout strain. Actinorhodin production is delayed and calcium-dependent antibiotic production is diminished, in the Δ<italic>SCO4117</italic> mutant. By contast, undecylprodigiosin production do not show significant variations. The expression of genes encoding secondary metabolism pathways (deoxysugar synthases, actinorhodin biosynthetic genes) and genes involved in differentiation (<italic>rdl, chp, nepA, ssgB</italic>) was dramatically reduced (up to 300-fold) in the <italic>SCO4117</italic> knockout. A putative motif bound, with the consensus “<underline>C</underline>S<underline>G</underline>YN-17bps-SRH<underline>A</underline>” sequence, was identified in the promoter region of 29 genes showing affected transcription in the <italic>SCO4117</italic> mutant, including one of the <italic>SCO4117</italic> promoters. <italic>SCO4117</italic> is a conserved gene with complex regulation at the transcriptional and post-translational levels and the first member of the ECF52 family characterized.</p>