A unique sigma/anti-sigma system in the actinomycete Actinoplanes missouriensis.

Tezuka, Takeaki; Mitsuyama, Kyota; Date, Risa; Ohnishi, Yasuo · Nat Commun · 2023

basic_science · Level V

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Abstract

Bacteria of the genus Actinoplanes form sporangia that contain dormant sporangiospores which, upon contact with water, release motile spores (zoospores) through a process called sporangium dehiscence. Here, we set out to study the molecular mechanisms behind sporangium dehiscence in Actinoplanes missouriensis and discover a sigma/anti-sigma system with unique features. Protein σ<sup>SsdA</sup> contains a functional sigma factor domain and an anti-sigma factor antagonist domain, while protein SipA contains an anti-sigma factor domain and an anti-sigma factor antagonist domain. Remarkably, the two proteins interact with each other via the anti-sigma factor antagonist domain of σ<sup>SsdA</sup> and the anti-sigma factor domain of SipA. Although it remains unclear whether the SipA/σ<sup>SsdA</sup> system plays direct roles in sporangium dehiscence, the system seems to modulate oxidative stress responses in zoospores. In addition, we identify a two-component regulatory system (RsdK-RsdR) that represses initiation of sporangium dehiscence.

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