Affiliation:
1. Department of Molecular Microbiology, John Innes Centre, Norwich, United Kingdom
2. Department of Cell and Developmental Biology, John Innes Centre, Norwich, United Kingdom
Abstract
ABSTRACT
WhiA is a highly unusual transcriptional regulator related to a family of eukaryotic homing endonucleases. WhiA is required for sporulation in the filamentous bacterium
Streptomyces
, but WhiA homologues of unknown function are also found throughout the Gram-positive bacteria. To better understand the role of WhiA in
Streptomyces
development and its function as a transcription factor, we identified the WhiA regulon through a combination of chromatin immunoprecipitation-sequencing (ChIP-seq) and microarray transcriptional profiling, exploiting a new model organism for the genus,
Streptomyces venezuelae
, which sporulates in liquid culture. The regulon encompasses ~240 transcription units, and WhiA appears to function almost equally as an activator and as a repressor. Bioinformatic analysis of the upstream regions of the complete regulon, combined with DNase I footprinting, identified a short but highly conserved asymmetric sequence, GACAC, associated with the majority of WhiA targets. Construction of a null mutant showed that
whiA
is required for the initiation of sporulation septation and chromosome segregation in
S. venezuelae
, and several genes encoding key proteins of the
Streptomyces
cell division machinery, such as
ftsZ
,
ftsW
, and
ftsK
, were found to be directly activated by WhiA during development. Several other genes encoding proteins with important roles in development were also identified as WhiA targets, including the sporulation-specific sigma factor σ
WhiG
and the diguanylate cyclase CdgB. Cell division is tightly coordinated with the orderly arrest of apical growth in the sporogenic cell, and
filP
, encoding a key component of the polarisome that directs apical growth, is a direct target for WhiA-mediated repression during sporulation.
IMPORTANCE
Since the initial identification of the genetic loci required for
Streptomyces
development, all of the
bld
and
whi
developmental master regulators have been cloned and characterized, and significant progress has been made toward understanding the cell biological processes that drive morphogenesis. A major challenge now is to connect the cell biological processes and the developmental master regulators by dissecting the regulatory networks that link the two. Studies of these regulatory networks have been greatly facilitated by the recent introduction of
Streptomyces venezuelae
as a new model system for the genus, a species that sporulates in liquid culture. Taking advantage of
S. venezuelae
, we have characterized the regulon of genes directly under the control of one of these master regulators, WhiA. Our results implicate WhiA in the direct regulation of key steps in sporulation, including the cessation of aerial growth, the initiation of cell division, and chromosome segregation.
Publisher
American Society for Microbiology
Cited by
104 articles.
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