Combinatorial Regulation of the<i>dev</i>Operon by MrpC2 and FruA during Myxococcus xanthus Development

Campbell, A.I.M.; Viswanathan, Poorna; Barrett, Terrance D.; Son, Bongjun; Saha, Shreya; Kroos, Lee

doi:10.1128/jb.02310-14

Cited by 23 publications

(68 citation statements)

References 60 publications

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“…MrpC and FruA are transcription factors that cooperatively bind to the dev promoter region and appear to activate transcription (9). Also, MrpC appears to activate transcription of fruA (15).…”

Section: Discussionmentioning

confidence: 99%

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The dev Operon Regulates the Timing of Sporulation during Myxococcus xanthus Development

Rajagopalan

Kroos

2017

J Bacteriol

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Myxococcus xanthus undergoes multicellular development when starved. Thousands of rod-shaped cells coordinate their movements and aggregate into mounds in which cells differentiate into spores. Mutations in the dev operon impair development. The dev operon encompasses a clustered regularly interspaced short palindromic repeat-associated (CRISPR-Cas) system. Null mutations in devI, a small gene at the beginning of the dev operon, suppress the developmental defects caused by null mutations in the downstream devR and devS genes but failed to suppress defects caused by a small in-frame deletion in devT. We provide evidence that the original mutant has a second-site mutation. We show that devT null mutants exhibit developmental defects indistinguishable from devR and devS null mutants, and a null mutation in devI suppresses the defects of a devT null mutation. The similarity of DevTRS proteins to components of the CRISPR-associated complex for antiviral defense (Cascade), together with our molecular characterization of dev mutants, support a model in which DevTRS form a Cascade-like subcomplex that negatively autoregulates dev transcript accumulation and prevents DevI overproduction that would strongly inhibit sporulation. Our results also suggest that DevI transiently inhibits sporulation when regulated normally. The mechanism of transient inhibition may involve MrpC, a key transcription factor, whose translation appears to be weakly inhibited by DevI. Finally, our characterization of a devI devS mutant indicates that very little exo transcript is required for sporulation, which is surprising since Exo proteins help form the polysaccharide spore coat.IMPORTANCE CRISPR-Cas systems typically function as adaptive immune systems in bacteria. The dev CRISPR-Cas system of M. xanthus has been proposed to prevent bacteriophage infection during development, but how dev controls sporulation has been elusive. Recent evidence supported a model in which DevR and DevS prevent overproduction of DevI, a predicted 40-residue inhibitor of sporulation. We provide genetic evidence that DevT functions together with DevR and DevS to prevent DevI overproduction. We also show that spores form about 6 h earlier in mutants lacking devI than in the wild type. Only a minority of natural isolates appear to have a functional dev promoter and devI, suggesting that a functional dev CRISPR-Cas system evolved recently in niches where delayed sporulation and/or protection from bacteriophage infection proved advantageous.KEYWORDS CRISPR-Cas, Myxococcus xanthus, bacterial development, dev operon, gene regulation, signaling, sporulation M yxococcus xanthus is a Gram-negative soil bacterium that exhibits social behaviors (1). In nature, cells of M. xanthus move in groups, feeding on prey bacteria and organic detritus. When starved, thousands of cells aggregate to form mounds that mature into fruiting bodies as rod-shaped cells differentiate into dormant ovoid spores.

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Section: Discussionmentioning

confidence: 99%

“…1). Since the dev operon is a direct target of transcriptional activation by MrpC and FruA (9), a simple model proposes that dev expression governs commitment to sporulation (5). However, recent work showed that deletion of the dev promoter or the first gene of the operon, devI, suppresses the sporulation defects of devR and devS mutants (10).…”

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The dev Operon Regulates the Timing of Sporulation during Myxococcus xanthus Development

Rajagopalan

Kroos

2017

J Bacteriol

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“…Combinatorial regulation by MrpC2 and FruA has been documented for four other developmental genes or operons of M. xanthus (19)(20)(21)(22) in addition to the dev operon (18). All of these genes and operons depend on C-signaling for expression during development (23)(24)(25)(26)(27).…”

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confidence: 99%

“…LadA binds to DNA about 350 bp downstream of the dev promoter (P dev ) and positively regulates transcription (17). MrpC2 appears to bind cooperatively with FruA to two sites upstream of P dev (18). Binding of the two transcription factors to a site located immediately upstream of P dev is necessary for expression.…”

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devIIs an Evolutionarily Young Negative Regulator of Myxococcus xanthus Development

et al. 2015

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During starvation-induced development of Myxococcus xanthus, thousands of rod-shaped cells form mounds in which they differentiate into spores. The dev locus includes eight genes followed by clustered regularly interspaced short palindromic repeats (CRISPRs), comprising a CRISPR-Cas system (Cas stands for CRISPR associated) typically involved in RNA interference. Mutations in devS or devR of a lab reference strain permit mound formation but impair sporulation. We report that natural isolates of M. xanthus capable of normal development are highly polymorphic in the promoter region of the dev operon. We show that the dev promoter is predicted to be nonfunctional in most natural isolates and is dispensable for development of a laboratory reference strain. Moreover, deletion of the dev promoter or the small gene immediately downstream of it, here designated devI (development inhibitor), suppressed the sporulation defect of devS or devR mutants in the lab strain. Complementation experiments and the result of introducing a premature stop codon in devI support a model in which DevRS proteins negatively autoregulate expression of devI, whose 40-residue protein product DevI inhibits sporulation if overexpressed. DevI appears to act in a cellautonomous manner since experiments with conditioned medium and with cell mixtures gave no indication of extracellular effects. Strikingly, we report that devI is entirely absent from most M. xanthus natural isolates and was only recently integrated into the developmental programs of some lineages. These results provide important new insights into both the evolutionary history of the dev operon and its mechanistic role in M. xanthus sporulation. IMPORTANCECertain mutations in the dev CRISPR-Cas (clustered regularly interspaced short palindromic repeat-associated) system of Myxococcus xanthus impair sporulation. The link between development and a CRISPR-Cas system has been a mystery. Surprisingly, DNA sequencing of natural isolates revealed that many appear to lack a functional dev promoter, yet these strains sporulate normally. Deletion of the dev promoter or the small gene downstream of it suppressed the sporulation defect of a lab strain with mutations in dev genes encoding Cas proteins. The results support a model in which the Cas proteins DevRS prevent overexpression of the small gene devI, which codes for an inhibitor of sporulation. Phylogenetic analysis of natural isolates suggests that devI and the dev promoter were only recently acquired in some lineages. Myxococcus xanthus is a Gram-negative bacterium of the deltaproteobacteria group. Typically found in the soil, M. xanthus exhibits social behaviors (1). The rod-shaped cells move in groups on solid surfaces, feeding on prey bacteria and organic matter. When starved, cells modify their movements and build mounds containing thousands of individuals that differentiate into ovoid spores. The resulting mound of dormant and insultresistant spores is called a fruiting body. Spores within the fruiting body germinate when con...

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“…Thus far, about 100 basic structures and 500 structural analogs have been discovered in myxobacteria and have been fully characterized chemically, which account for about 3.5% of the presently known secondary metabolites of microbial origin [5][6]. The diversity of the chemical structures and action mechanisms of the metabolites from myxobacteria can even be compared with those from Streptomyces [7][8]. Therefore, myxobacteira are not only important in fundamental studies, but also alluring by industrial application.…”

Section: Introductionmentioning

confidence: 99%

Optimization of Protoplast Formation, Regeneration, and Viability of Myxobacteria

Jiang¹,

Qiu²,

Li³

2015

Advances in Chemical Science

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Combinatorial Regulation of thedevOperon by MrpC2 and FruA during Myxococcus xanthus Development

Cited by 23 publications

References 60 publications

The dev Operon Regulates the Timing of Sporulation during Myxococcus xanthus Development

The dev Operon Regulates the Timing of Sporulation during Myxococcus xanthus Development

devIIs an Evolutionarily Young Negative Regulator of Myxococcus xanthus Development

Optimization of Protoplast Formation, Regeneration, and Viability of Myxobacteria

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