Project description:Background: The 6S RNA is a global transcriptional riboregulator, which is exceptionally widespread among most bacterial phyla. While its role is well-characterized in some heterotrophic bacteria, we subjected a cyanobacterial homolog to functional analysis, thereby extending the scope of 6S RNA action to the special challenges of photoautotrophic lifestyles. Results: Physiological characterization of a 6S RNA deletion strain (ΔssaA) demonstrates a delay in the recovery from nitrogen starvation. Significantly decelerated phycobilisome reassembly and glycogen degradation are accompanied with reduced photosynthetic activity compared to the wild type. Transcriptome profiling further revealed that predominantly genes encoding photosystem components, ATP synthase, phycobilisomes and ribosomal proteins were negatively affected in ΔssaA. In vivo pull-down studies of the RNA polymerase complex indicated that the presence of 6S RNA promotes the recruitment of the cyanobacterial housekeeping σ factor SigA, concurrently supporting dissociation of group 2 σ factors during recovery from nitrogen starvation. Conclusions: The combination of genetic, physiological and biochemical studies reveals the homologue of 6S RNA as an integral part of the cellular response of Synechocystis sp. PCC 6803 to changing nitrogen availability. According to these results, 6S RNA supports a rapid acclimation to changing nitrogen supply by accelerating the switch from group 2 σ factors SigB, SigC and SigE to SigA-dependent transcription. We therefore introduce the cyanobacterial 6S RNA as a novel candidate regulator of RNA polymerase sigma factor recruitment in Synechocystis sp. PCC 6803. Further studies on mechanistic features of the postulated interaction should shed additional light on the complexity of transcriptional regulation in cyanobacteria.
Project description:Legionella pneumophila is a gram-negative opportunistic human pathogen that infects and multiplies in a broad range of phagocytic protozoan and mammalian phagocytes. Based on the observation that small regulatory RNAs (sRNAs) play an important role in controlling virulence-related genes in several pathogenic bacteria, we attempted to test the hypothesis that sRNAs play a similar role in L. pneumophila. We used computational prediction followed by experimental verification to identify and characterize sRNAs encoded in the L. pneumophila genome. A 50-mer probe microarray was constructed to test the expression of predicted sRNAs in bacteria grown under a variety of conditions. This strategy successfully identified 22 expressed RNAs, out of which six were confirmed by northern blot and RACE. One of the identified sRNAs is highly expressed when the bacteria enter post exponential phase and computational prediction of its secondary structure reveals a striking similarity to the structure of 6S RNA, a widely distributed prokaryotic sRNA, known to regulate the activity of σ70-containing RNAP. A 70-mer probe microarray was used to identify genes affected by L. pneumophila 6S RNA in stationary phase. The 6S RNA encoded by the ssrS gene positively regulates expression of genes encoding type IVB secretion system effectors, stress response genes such as groES and recA as well as many genes with unknown or hypothetical functions. Deletion of 6S RNA significantly reduced L. pneumophila intracellular multiplication in both protist and mammalian host cells, but had no detectable effect on growth in rich media.
Project description:Metagenome data from soil samples were collected at 0 to 10cm deep from 2 avocado orchards in Channybearup, Western Australia, in 2024. Amplicon sequence variant (ASV) tables were constructed based on the DADA2 pipeline with default parameters.
Project description:The 6S RNA is a global transcriptional riboregulator, which is exceptionally widespread among most bacterial phyla. While its role is already well-characterized in heterotrophic bacteria, we subjected a cyanobacterial homolog to functional analysis, thereby extending the scope of 6S RNA action to the special challenges of photoautotrophic lifestyles. This study reveals 6S RNA as an integral part of the cellular response of Synechocystis sp. PCC 6803 to changing nitrogen availability. Physiological characterization of a 6S RNA deletion strain (ÎssaA) demonstrates a delay in the recovery from nitrogen starvation. Significantly decelerated phycobilisome reassembly and glycogen degradation is accompanied with reduced photosynthetic activity compared to the wild type. Transcriptome profiling further revealed that predominantly genes encoding components of both photosystems, ATP synthase and the phycobilisomes were negatively affected in the ÎssaA mutant. In vivo pull-down studies of the RNA polymerase complex further indicate a promoting effect of 6S RNA on the recruitment of the cyanobacterial housekeeping sigma factor SigA, concurrently supporting dissociation of group II sigma factors during recovery from nitrogen starvation. According to these results, 6S RNA supports a rapid adaptation to changing nitrogen conditions by regulating the switch from group II sigma factors SigB / SigC to SigE / SigA dependent transcription. We performed microarray analysis of total RNA from wild-type and âssaA cultures that were starved for nitrogen for seven days and recovered over a period of 48 hours. Sampling time points were t1 = 1h +N, t2 = 4h +N and t3 = 22h +N after nitrogen recovery. Samples were taken in biological replicates.
Project description:This SuperSeries is composed of the following subset Series: GSE19196: Detection of predicted small RNA of Legionella pneumophila GSE19200: Gene affected by deletion of 6S RNA in post-exponential phase Refer to individual Series
Project description:RNA sequencing (RNA-seq) has become a standard method for quantifying gene expression transcriptome-wide. Due to the extremely high proportion of ribosomal RNA (rRNA) in total RNA, sequencing libraries usually incorporate messenger RNA (mRNA) enrichment. Although polyadenylate (poly(A)) tail selection is widely used, many applications require alternate approaches such as rRNA depletion. Recently, selective rRNA digestion, using RNaseH and antisense DNA oligomers that tile the length of target RNAs, has emerged as an easy, cost-effective alternative to commercial rRNA depletion kits. Here, we present a streamlined RNaseH-mediated rRNA depletion method that uses shorter antisense oligos that only sparsely tile the target RNA, in a digestion reaction of only 5 minutes. We wrote a Web tool, Oligo-ASST, that simplifies oligo design to favor target regions with optimal thermodynamic properties, and additionally allows users to design common oligo pools that can simultaneously target divergent RNAs in their regions of higher sequence similarity. We demonstrate the efficacy of these oligos by building rRNA-depleted sequencing libraries for Xenopus laevis as well as zebrafish, which expresses two distinct versions of the 28S, 18S, 5.8S, and 5S rRNAs during embryogenesis. These libraries efficiently deplete rRNA to <5% of total reads, on par with poly(A) selection, and also reveal expression of many non-adenylated RNA species. Oligo-ASST is freely available at https://mtleelab.pitt.edu/oligo to design antisense oligos for any taxon or to target any abundant RNA for depletion.
Project description:Legionella pneumophila is a gram-negative opportunistic human pathogen that infects and multiplies in a broad range of phagocytic protozoan and mammalian phagocytes. Based on the observation that small regulatory RNAs (sRNAs) play an important role in controlling virulence-related genes in several pathogenic bacteria, we attempted to test the hypothesis that sRNAs play a similar role in L. pneumophila. We used computational prediction followed by experimental verification to identify and characterize sRNAs encoded in the L. pneumophila genome. A 50-mer probe microarray was constructed to test the expression of predicted sRNAs in bacteria grown under a variety of conditions. This strategy successfully identified 22 expressed RNAs, out of which six were confirmed by northern blot and RACE. One of the identified sRNAs is highly expressed when the bacteria enter post exponential phase and computational prediction of its secondary structure reveals a striking similarity to the structure of 6S RNA, a widely distributed prokaryotic sRNA, known to regulate the activity of Ï70-containing RNAP. A 70-mer probe microarray was used to identify genes affected by L. pneumophila 6S RNA in stationary phase. The 6S RNA encoded by the ssrS gene positively regulates expression of genes encoding type IVB secretion system effectors, stress response genes such as groES and recA as well as many genes with unknown or hypothetical functions. Deletion of 6S RNA significantly reduced L. pneumophila intracellular multiplication in both protist and mammalian host cells, but had no detectable effect on growth in rich media. The 70-mer microarray representing all annotated ORFs of L. pneumophila has been previously described (Charpentier et al., 2008). RNA was extracted from ssrS mutant strain and the wild-type strain grown to PE phase. gDNA was used as a reference channel on each slides. Labelling of samples, hybridization strategy and data acquisition were performed as described in the Methods section. Local background was removed from spot signal intensity and normalization was carried out by calculating the fraction over the total signal intensity in both channel as previously described (Faucher et al., 2006). Signal levels that were lower than background in experiments and controls were filtered out. A total of six cDNA to reference ratios were recorded for each time point. Statistical analysis between mutant and wild-type strain was performed using unpaired one-tailed studentâs t-test. Genes were considered as differentially expressed if they demonstrated a ratio to control value of ±2-fold with a p < 0.001.