GrgA overexpression inhibits Chlamydia trachomatis growth through sigma66- and sigma28-dependent mechanisms

Zou²,

Weber

et al. 2021

mSystems

Self Cite

Chlamydia trachomatis is the most prevalent sexually transmitted bacterial pathogen worldwide and is a leading cause of preventable blindness in underdeveloped areas as well as some developed countries. Chlamydia carries genes that encode a limited number of known transcription factors. While Euo is thought to be critical for early chlamydial development, the functions of GrgA and HrcA in the developmental cycle are unclear.

Section: Methodssupporting

confidence: 51%

Section: Methodssupporting

confidence: 51%

Section: Resultsmentioning

confidence: 99%

“…Phase contrast and RFP images were acquired at 35 hpi ( 73 ). The Java-based ImageJ software was then used to quantify RFP intensities ( 4 ).…”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Identification of a GrgA-Euo-HrcA Transcriptional Regulatory Network in Chlamydia

Zou²,

Weber

et al. 2021

mSystems

Self Cite

Requirement of GrgA forChlamydiainfectious progeny production

Wang

et al. 2023

Preprint

Self Cite

Hallmarks of the developmental cycle of the obligate intracellular pathogenic bacterium Chlamydia are the primary differentiation of the infectious elementary body (EB) cell type into the proliferative reticulate body (RB) and the secondary differentiation of RBs back into EBs. The detailed mechanisms regulating these transitions are unclear. In this study, we developed a novel strategy termed DOPE (dependence on plasmid-mediated expression) that allows for the knockdown of essential genes in Chlamydia. Importantly, we demonstrate that GrgA, a Chlamydia-specific transcription factor, is essential for the secondary differentiation of RBs into EBs. Our development of a conditional GrgA-deficient chlamydiae should prove valuable for future studies examining chlamydial growth, development, and pathogenicity. Furthermore, because EB formation is absolutely required for chlamydial dissemination within infected individuals, and for chlamydial transmission to new hosts, our maturation-defective chlamydiae system may serve as an attractive attenuated vaccine methodology for the prevention of chlamydial diseases.

Requirement of GrgA forChlamydiainfectious progeny production, optimal growth, and efficient plasmid maintenance

Lü

Wang

et al. 2023

Preprint

Chlamydia, an obligate intracellular bacterial pathogen, has a unique developmental cycle involving the differentiation of invading elementary bodies (EBs) to noninfectious reticulate bodies (RBs), replication of RBs, and redifferentiation of RBs into progeny EBs. Progression of this cycle is regulated by three sigma factors, which direct the RNA polymerase to their respective target gene promoters. We hypothesized that theChlamydia-specific transcriptional regulator GrgA, previously shown to activate σ66 and σ28, plays an essential role in chlamydial development and growth. To test this hypothesis, we applied a novel genetic tool known as dependence on plasmid-mediated expression (DOPE) to createChlamydia trachomatiswith conditional GrgA-deficiency. We show that GrgA-deficientC. trachomatisRBs have a growth rate that is approximately half of the normal rate and fail to transition into progeny EBs. In addition, GrgA-deficientC. trachomatisfail to maintain its virulence plasmid. Results of RNA-seq analysis indicate that GrgA promotes RB growth by optimizing tRNA synthesis and expression of nutrient-acquisition genes, while it enables RB-to-EB conversion by facilitating the expression of a histone and outer membrane proteins required for EB morphogenesis. GrgA also regulates numerous other late genes required for host cell exit and subsequent EB invasion into host cells. Importantly, GrgA stimulates the expression of σ54, the third and last sigma factor, and its activator AtoC, and thereby indirectly upregulating the expression of σ54-dependent genes. In conclusion, our work demonstrates that GrgA is a master transcriptional regulator inChlamydiaand plays multiple essential roles in chlamydial pathogenicity.IMPORTANCEHallmarks of the developmental cycle of the obligate intracellular pathogenic bacteriumChlamydiaare the primary differentiation of the infectious elementary body (EB) into the proliferative reticulate body (RB) and the secondary differentiation of RBs back into EBs. The mechanisms regulating these transitions remain unclear. In this report, we developed an effective novel strategy termed DOPE that allows for the knockdown of essential genes inChlamydia. We demonstrate that GrgA, aChlamydia-specific transcription factor, is essential for the secondary differentiation and optimal growth of RBs. We also show that GrgA, a chromosome-encoded regulatory protein, controls the maintenance of the chlamydial virulence plasmid. Transcriptomic analysis further indicates that GrgA functions as a critical regulator of all three sigma factors that recognize different promoter sets at developmental stages. The DOPE strategy outlined here should provide a valuable tool for future studies examining chlamydial growth, development, and pathogenicity.