Abstract
Host-pathogen interactions are highly complex, involving large dynamic changes in gene expression during infection. These interactions are fundamental to understanding anti-infection immunity of hosts, as well as the pathogenesis of pathogens. For bacterial pathogens interacting with animal hosts, time-resolved dual RNA-seq of infected tissue is difficult to perform due to low pathogen load in infected tissue. In this study, an acute infection model of Larimichthys crocea infected by Pseudomonas plecoglossicida was established. The spleens of infected fish exhibited typical symptoms, with a maximum bacterial load at two days post-injection (dpi). Time-resolved dual RNA-seq of infected spleens was successfully applied to study host-pathogen interactions between L. crocea and P. plecoglossicida. The spleens of infected L. crocea were subjected to dual RNA-seq, and transcriptome data were compared with those of noninfected spleens or in vitro cultured bacteria. Results showed that pathogen-host interactions were highly dynamically regulated, with corresponding fluctuations in host and pathogen transcriptomes during infection. The expression levels of many immunogenes involved in cytokine-cytokine receptor, Toll-like receptor signaling, and other immune-related pathways were significantly up-regulated during the infection period. Furthermore, metabolic processes and the use of oxygen in L. crocea were strongly affected by P. plecoglossicida infection. The WGCNA results showed that the metabolic process was strongly related to the entire immune process. For P. plecoglossicida, the expression levels of motility-related genes and flagellum assembly-related genes were significantly up-regulated. The results of this study may help to elucidate the interactions between L. crocea and P. plecoglossicida.
Highlights
Large yellow croakers (Larimichthys crocea), a marine fish with the largest annual yield in China, are widely cultured in Fujian and Zhejiang provinces (Sun et al, 2019a; Yang et al, 2016)
The first death of L. crocea was recorded at 2.5 dpi, and the last death was recorded at 4.5 dpi (Tang et al, 2019c)
All L. crocea counterparts from the CG that received intrapleural injections of phosphate-buffered saline (PBS) survived the experimental period
Summary
Large yellow croakers (Larimichthys crocea), a marine fish with the largest annual yield in China, are widely cultured in Fujian and Zhejiang provinces (Sun et al, 2019a; Yang et al, 2016). The “visceral white spot disease” caused by Pseudomonas plecoglossicida is one of the most destructive diseases of L. crocea, causing considerable economic losses (Huang et al, 2018; Zhang et al, 2014). This pathogen infects large yellow croakers but is the causative agent of bacterial hemorrhagic ascites disease in Plecoglossus altivelis (Nishimori et al, 2000). P. plecoglossicida infection (104 colony forming units per gram (cfu/g)) resulted in 100% L. crocea death rate at 4.5 days post-injection (dpi) (Tang et al, 2019c), indicating that P. plecoglossicida is more virulent than most other aquatic pathogens, including Vibrio alginolyticus (Huang et al, 2017; Liu et al, 2017) and Aeromonas hydrophila (Zhang et al, 2018b, 2019c). In view of the considerable damage caused by P. plecoglossicida to aquaculture, its pathogenic mechanism has attracted the attention of researchers (Huang et al, 2018; Tao et al, 2016), resulting in the identification of several virulence genes (Luo et al, 2019a; Zhang et al, 2019a)
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