Project description:Many reports show an association between the Pst system, the Pho regulon related genes and bacterial virulence. Our previous results showed that a functional Pst system is required for full virulence, resistance to serum, polymyxin B and acid shock. However, the interplay between the Pst system and virulence has an unknown molecular basis. To understand global APEC virulent strain responses to Pho regulon activation, we conducted transcriptome profiling experiments comparing the APEC chi7122 strain and its isogenic Pst mutant grown in rich phosphate medium using the Affymetrix GeneChip® E. coli Genome 2.0 Array. The Affymetrix GeneChip® E. coli Genome 2.0 Array contains the genome of the E. coli MG1655 and three pathogenic E. coli strain (EDL933, Sakai and CFT073) representing 20,366 genes. While comparing genes expression between Pst mutant and the wild type chi7122 strain, 471 genes are either up- (254) or down-regulated (217) of at least 1.5-fold, with a p-value inferior or equal to 0.05 and a false discovery rate of 2.71%. Keywords: Escherichia coli, phosphate starvation response, Pho regulon, Pst system, Affymetrix, transcriptional analysis
Project description:Purpose: This study is to more comprehensively understand the genome-wide host response to avian pathogen E. coli (APEC). Methods: Male broiler chicks were challenged with APEC (or mock-challenged as controls), and bone marrow was harvested at 1 and 5 days post-infection (dpi). Based upon necropsy-scored lesions on liver, pericardium, and air sacs, the challenged birds were assigned to mild or severe pathology categories, representing resistant and susceptible phenotypes, respectively. RNA sequence data were first analyzed using the R package EdgeR to identify differentially expressed genes.GO and pathway analysis using the R package GOseq identified many immune-related pathways. Results: RNA sequencing resulted in 11 to 40 million single-end raw reads of 100 bp per sample. After alignment, an average of 80 % of the reads, with 5 % representing multiple mapping, were mapped to the chicken reference transcriptome. Among these detected unique transcripts, there were 2,404 novel genes mainly distributed on chromosomes 1, 2, 4, 3, Z, 5 in decreasing number. Genes were detected as differentially expressed (DE) between treatments (susceptible, resistant, and mock-challenged) at a given time point, or DE between 1 and 5 dpi within the same treatment group. Compared to mock-challenged birds on 5 dpi, susceptible birds exhibited extensive enhancement of their T cell and B cell development, as well as innate and adaptive immune response. However, for the 1 dpi group, susceptible birds exhibited a decreased gene expression of T and B cell development. The differences between the two phenotypes, susceptible and resistant birds, at 5 dpi showed that susceptible birds had increased gene expression of B-cell development and adaptive immune response. Conclusions: This is the first report to our knowledge examining the role of bone marrow cells in responding to APEC infection in broilers. This transcriptome study provides insight and global overview into the response of genes involved in the earliest phases of the immune response to APEC infection. Our data indicate a dynamic interaction between the innate and adaptive immune responses to APEC infection in susceptible birds, providing flexibility and redundancy in the host’s induction of cytokines and chemokines. Additionally, B cell and T cell development are also extensively affected by APEC infection for susceptible birds, resulting in drastic host impairment in early response to infection. The findings of present study shed light on the underlying chicken immune modulation against APEC infection. Also, this study will build a solid foundation for identifying host genetic variation that may be manipulated to enhance resistance to infection and may be useful as colibacillosis control targets.