RNA-Seq analysis of the Neisseria gonorrhoeae GntR-type transcriptional regulator GdhR

In this work we have determined by RNA-Seq the whole set of genes regulated by the N. gonorrhoeae GdhR transcriptional regulator (NGO1360 gene in reference strain FA1090). The results showed that GdhR regulates the expression of 2.3% of all the genes in the gonococcal (strain FA19) genome, of which 39 were activated and 11 were repressed. Most of the GdhR-regulated genes lie in the category of fimbrial proteins and membrane antigens or transporters. GdhR was found not be a cryptic regulator since there is an overlap in the set of GdhR-regulated genes between the wild type and a strain expressing gdhR ectopically from the lac promoter. Among the GdhR-regulated genes linked to gonococcal pathogenesis we found that lctP, encoding a unique L-lactate transporter, was the highest of GdhR-repressed genes. Total RNA samples were isolated from N. gonorrhoeae cultures grown to late exponential phase (OD600 1.0), depleted from ribosomal RNA and subjected to paired-end high throughput sequencing on the Illumina NextSeq 500 platform (Illumina Inc., San Diego, CA). Each strain (condition) was sequenced in duplicates. Transcript differential expression analyses were conducted between the transcriptomes of a wild type FA19 strain and its isogenic gdhR mutant, and between the gdhR mutant and its complemented strain expressing gdhR ectopically from the lac promoter.