CsmR controls both, motility and cell shape, in Haloferax volcanii

Area of Science:

• Microbiology
• Molecular Biology
• Archaea Research

Background:

• Archaea utilize motility and morphological plasticity for environmental navigation.
• Transcriptional regulation of these processes in archaea, particularly Haloferax volcanii, is not well understood.
• H. volcanii lacks the EarA-like regulator found in other Euryarchaeota for archaellum gene transcription.

Purpose of the Study:

• To identify transcriptional regulators governing archaellum biogenesis and cell shape in Haloferax volcanii.
• To elucidate the regulatory network controlling motility and morphology in haloarchaea.

Main Methods:

• Comparative transcriptomics to define the CsmR regulon.
• Chromatin immunoprecipitation sequencing (ChIP-seq) to identify CsmR binding sites.
• Deletion and overexpression studies of the csmR gene.
• Northern blotting and cell shape observations.

Main Results:

• CsmR was identified as a transcriptional regulator controlling archaellum biogenesis and cell shape transitions.
• Deletion of csmR abolished motility; overexpression enhanced motility and promoted a rod-like shape.
• The CsmR regulon includes archaellum, chemotaxis, and cell-shape genes (Sph3, RdfA).
• CsmR directly binds to promoter-proximal regions of target genes.
• CsmR and CirA (KaiC-like regulator) exhibit overlapping transcriptional regulation, with CirA potentially modulating CsmR via post-translational modification.
• RosR influences a regulatory RNA overlapping with cirA, potentially fine-tuning CirA's effect on archaellum genes and cell shape determinants.

Conclusions:

• CsmR is a crucial regulator of archaellum gene expression and cell shape in H. volcanii.
• Haloarchaea coordinate motility and morphology through an intricate transcriptional network involving CsmR and potentially CirA and RosR.
• This study offers insights into archaeal adaptability and prokaryotic cell biology regulation.