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Gene expression changes during overexpression of bacterial small RNA, DicF

ABSTRACT: Hundreds of small RNAs (sRNAs) have been identified in diverse bacterial species, and while the functions of most remain unknown, some regulate key processes, particularly stress responses. The sRNA DicF was identified over twenty-five years ago as an inhibitor of cell division, but since then has remained uncharacterized. DicF is 53 nucleotides and is encoded on a prophage (Qin) in the genomes of many Escherichia coli strains. Here, we performed RNA-Seq analyses of an E. coli strain with chromosomal deletion of dicF and overexpressing either empty plasmid or dicF from a plasmid. Systems analysis using computational methods identified additional mRNA targets of DicF: xylR and pykA mRNAs, encoding the xylose uptake and catabolism regulator and pyruvate kinase, respectively. We have further validated these target genes experimentally.

ORGANISM(S): Escherichia coli str. K-12 substr. MG1655

PROVIDER: GSE76916 | GEO | 2016/01/16

SECONDARY ACCESSION(S): PRJNA308934

REPOSITORIES: GEO

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Project description:Strains of Pseudomonas putida have emerged as promising biocatalysts for the conversion of sugars and aromatics obtained from lignocellulosic biomass. Understanding the role of carbon catabolite repression (CCR) in these strains is critical to optimizing the conversion of biomass to fuels and chemicals. The functioning of CCR in a P. putida strain, P. putida M2, capable of growing on both hexose and pentose sugars as well as aromatics, was investigated by cultivation experiments, proteomics, and CRISPRi-based gene repression. Strain M2 was able to co-utilize sugars and aromatics simultaneously; however, during co-cultivation with glucose and phenylpropanoid aromatics (p-coumarate and ferulate), intermediates (4-hydroxybenzoate and vanillate) accumulated, and substrate consumption was incomplete. In contrast, xylose-aromatic consumption resulted in transient intermediate accumulation and complete aromatic consumption, while xylose was incompletely consumed. Proteomics analysis of these co- cultivations revealed that glucose exerted stronger repression compared to xylose on the proteins involved in aromatic catabolism. Key glucose (Eda) and xylose (XylX) catabolic proteins were also identified at lower abundance during co-cultivation with aromatics implying simultaneous catabolite repression by sugars and aromatics. Downregulation of crc mediated by CRISPRi led to faster growth and uptake of both glucose and p-coumarate in the CRISPRi strains compared to the control while no difference was observed on xylose + p-coumarate. The increased abundance of the Eda protein and amino acids biosynthesis proteins in the CRISPRi strain further supported these observations. Lastly, small RNAs (sRNAs) sequencing results showed that the levels of CrcY and CrcZ homologs in M2, previously identified as sRNAs involved in CCR in P. putida strains, were lower under strong CCR (glucose + p-coumarate) condition compared to when repression was absent (p-coumarate or glucose only).

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Gene expression changes during overexpression of bacterial small RNA, DicF

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