Abstract
Avibacterium paragallinarum is the pathogen of infectious coryza, which is a highly contagious respiratory disease of chickens that brings a potentially serious threat to poultry husbandry. Iron is an important nutrient for bacteria and can be obtained from surroundings such as siderophores and hemophores. To date, the mechanisms of iron acquisition and heme utilization as well as detailed regulation in A. paragallinarum have been poorly understood. In this study, we investigated the transcriptomic profiles in detail and the changes of transcriptomes induced by iron restriction in A. paragallinarum using RNA-seq. Compared with the iron-sufficiency control group, many more differentially expressed genes (DEGs) and cellular functions as well as signaling pathways were verified in the iron-restriction group. Among these DEGs, the majority of genes showed decreased expression and some were found to be uniquely present in the iron-restriction group. With an in-depth study of bioinformatic analyses, we demonstrated the crucial roles of the Hut protein and DUF domain-containing proteins, which were preferentially activated in bacteria following iron restriction and contributed to the iron acquisition and heme utilization. Consequently, RT-qPCR results further verified the iron-related DEGs and were consistent with the RNA-seq data. In addition, several novel sRNAs were present in A. paragallinarum and had potential regulatory roles in iron homeostasis, especially in the regulation of Fic protein to ensure stable expression. This is the first report of the molecular mechanism of iron acquisition and heme utilization in A. paragallinarum from the perspective of transcriptomic profiles. The study will contribute to a better understanding of the transcriptomic response of A. paragallinarum to iron starvation and also provide novel insight into the development of new antigens for potential vaccines against infectious coryza by focusing on these iron-related genes.
Highlights
Infectious coryza, caused by Gram-negative bacterium Avibacterium paragallinarum, is a severe respiratory disease of chickens that brings enormous economic losses for the poultry industry worldwide (Blackall, 1999)
The cells were grown in a shaking incubator at 37◦C until reaching an optical density (OD) of 0.6-1.0 at 600 nm, and samples were harvested by centrifugation, followed immediately by being resuspended in RNA later (Ambion, Carlsbad, CA, United States)
We investigate the more profound transcriptomic profiles for the first time and illustrate changes of transcriptomes in A. paragallinarum in response to starvation using RNAseq
Summary
Infectious coryza, caused by Gram-negative bacterium Avibacterium paragallinarum, is a severe respiratory disease of chickens that brings enormous economic losses for the poultry industry worldwide (Blackall, 1999). In South Africa, it is considered as one of the most serious diseases, with C3 being the predominant serovar (Bragg et al, 1996; Boucher et al, 2014). The advent of multidrug bacterial resistance is deemed one of the most alarming situations worldwide. It is urgent for the development of novel broad-spectrum prophylactic agents against A. paragallinarum. The molecular mechanisms of colonization, growth, and virulence of A. paragallinarum in chicken upper respiratory tract are still poorly understood
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