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| Understanding transcription has been a central goal
of the scientific community for decades. However,
much is still unknown, especially concerning how it
is regulated. In bacteria, a single DNA-directed RNA-polymerase
performs the whole of transcription. It
contains multiple subunits, among which the s factor
that confers promoter specificity. Besides the housekeeping
s factor, bacteria encode several alternative
s factors. The most abundant and diverse family
of alternative s factors, the extracytoplasmic function
(ECF) family, regulates transcription of genes
associated with stressful scenarios, making them
key elements of adaptation to specific environmental
changes. Despite this, the evolutionary history of
ECF s factors has never been investigated. Here,
we report on our analysis of thousands of members
of this family. We show that single events are
in the origin of alternative modes of regulation of
ECF s factor activity that require partner proteins, but
that multiple events resulted in acquisition of regulatory
extensions. Moreover, in Bacteroidetes there
is a recent duplication of an ecologically relevant
gene cluster that includes an ECF s factor, whereas
in Planctomycetes duplication generates distinct C-terminal
extensions after fortuitous insertion of the
duplicated s factor. At last, we also demonstrate horizontal
transfer of ECF s factors between soil bacteria. | |
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