Investigation of Proteus vulgaris and Elizabethkingia meningoseptica invasion on muscle oxidative stress and autophagy in Chinese soft-shelled turtle (Pelodiscus sinensis).

Muscle is an important structural tissue in aquatic animals and it is susceptible to bacterial and fungal infection, which could affect flesh quality and health. In this study, Chinese soft-shelled turtles were artificially infected with two pathogens, Proteus vulgaris and Elizabethkingia meningoseptica and the effects on muscle nutritional characteristics, oxidative stress and autophagy were assayed. Upon infection, the muscle nutritional composition and muscle fiber structure were notably influenced. Meanwhile, the mRNA expression of Nrf2 was down-regulated and Keap1 up-regulated, thus resulting in a decrease in antioxidant capacity and oxidative stress. However, with N-acetylcysteine treatment, the level of oxidative stress was decreased, accompanied by significant increases in antioxidant enzyme activities and the mRNA levels of SOD, CAT, GSTCD, and GSTO1. Interestingly, there was a significant increase in autophagy in the muscle tissue after the pathogen infection, but this increase could be reduced by N-acetylcysteine treatment. Our findings suggest that muscle nutritional characteristics were dramatically changed after pathogen infection, and oxidative stress and autophagy were induced by pathogen infection. However, N-acetylcysteine treatment could compromise the process perhaps by decreasing the ROS level and regulating Nrf2-antioxidant signaling pathways.

Global analysis of transcriptome sequences highlights accelerated evolution of immune genes in Danio choprae and Danio albolineatus.

Danio fishes, a small type animal with short sexual cycles, are model vertebrate species. To investigate the genic evolution of this genus, the transcriptomes from Danio choprae and Danio albolineatus were sequenced by Illumina HiSeq 4000 platform. A total of 128,427,304 sequence reads from two Danio fishes were generated by Next Generation Sequencing. The resulting in two assemblies contained 88,682 and 88,029 unigenes in the Danio choprae and Danio albolineatus. Analysis of the orthologs from the Danio choprae and Danio albolineatus provided consistent evidence for the accelerated genic evolution in the Danio fishes. Several genes referring to immune functions under positive selection were identified by branch site model analysis, such as REL, GTF2E1, STAT6, MPG in Danio choprae and CYP17A1, ADORA2A, MYCN in Danio albolineatus. Our data provide novel insights into the adaptation in Danio fishes and is useful for understanding the genetic basis of adaptation in zebrafish.