Article published by the Endocrine Society Article published by the Endocrine Society

The natural sex reversal severely affects the sex ratio and thus decreases the productivity of the rice field eel (Monopterus albus). How to understand and manipulate this process is one of the major issues for the rice field eel stocking. So far the genomics and transcriptomics data available for this species are still scarce. Here we provide a comprehensive study of transcriptomes of brain and gonad tissue in three sex stages (female, intersex and male) from the rice field eel to investigate changes in transcriptional level during the sex reversal process. Approximately 195 thousand unigenes were generated and over 44.4 thousand were functionally annotated. Comparative study between stages provided multiple differentially expressed genes in brain and gonad tissue. Overall 4668 genes were found to be of unequal abundance between gonad tissues, far more than that of the brain tissues (59 genes). These genes were enriched in several different signaling pathways. A number of 231 genes were found with different levels in gonad in each stage, with several reproduction-related genes included. A total of 19 candidate genes that could be most related to sex reversal were screened out, part of these genes’ expression patterns were validated by RT-qPCR. The expression of spef2, maats1, spag6 and dmc1 were abundant in testis, but was barely detected in females, while the 17β-hsd12, zpsbp3, gal3 and foxn5 were only expressed in ovary. This study investigated the complexity of brain and gonad transcriptomes in three sex stages of the rice field eel. Integrated analysis of different gene expression and changes in signaling pathways, such as PI3K-Akt pathway, provided crucial data for further study of sex transformation mechanisms.

Macrophages are very versatile immune cells, with the characteristics of a proinflammatory phenotype in response to pathogen-associated molecular patterns. However, the specific activation marker genes of macrophages have not been systematically investigated in teleosts. In this work, leukocytes (WBC) were isolated using the Percoll gradient method. Macrophages were enriched by the adherent culture of WBC, then stimulated with lipopolysaccharide (LPS). Macrophages were identified by morphological features, functional activity and authorized cytokine expression. Subsequently, we collected samples, constructed and sequenced transcriptomic libraries including WBC, resting macrophage (Mø) and activated macrophage (M(LPS)) groups. We gained a total of 20.36 Gb of clean data including 149.24 million reads with an average length of 146 bp. Transcriptome analysis showed 708 differential genes between WBC and Mø, 83 differentially expressed genes between Mø and M(LPS). Combined with RT-qPCR, we proposed that four novel cell surface marker genes (CD22-like, CD63, CD48 and CD276) and two chemokines (CXCL-like and CCL39.3) would be emerging potential marker genes of macrophage in grass carp. Furthermore, CD69, CD180, CD27, XCL32a.2 and CXCL8a genes can be used as marker genes to confirm whether macrophages are activated. Transcriptome profiling reveals novel molecules associated with macrophages in C. Idella, which may represent a potential target for macrophages activation.

In November 2017, a group of farmed rainbow trout (Oncorhynchus mykiss) died in Yunnan Province, China, likely due to infection. These rainbow trout exhibited slow movement, no feeding, dark body color, exophthalmia, and occasional ulcers on the body surface. Pathogens were isolated from diseased rainbow trout livers, head kidneys, spleens, and eyes, and the strain was preliminarily identified as Acinetobacter johnsonii based on morphology, biochemical tests, and 16S rRNA and rpoB sequences. The isolated strains were highly sensitive to florfenicol, ciprofloxacin, oxolinic acid, and norfloxacin but resistant to ampicillin, doxycycline, sulfadiazine, thiamphenicol, and sulfamethazine. The selected isolate was performed for the experimental infection of rainbow trout to confirm its pathogenicity. Experimentally infected fish showed disease symptoms similar to those observed in fish naturally infected with these bacteria. Vacuolar degeneration was prevalent in the liver and spleen of diseased fish. Cytoplasm volume was very high in the lymphocytes of the head kidney. The protein structure and topology of monomeric outer membrane protein A (OmpA), outer membrane protein 34 (Omp34), and a nucleoside-specific outer membrane transporter protein Tsx (OmpTsx) of A. johnsonii were predicted by AlphaFold 2. The predicted local distance difference test (pLDDT) score was used for the assessment of structure prediction. Comprehensive analysis of antigenic determinants of the OMP family member, OmpA, contains three antigenic determinants, which are 90 similar with epitopes of A. baumannii. OmpA is a recombinant protein with 35kDa expressed in the Escherichia coli system. Based on these findings, A. johnsonii is regarded as an emerging opportunistic pathogen in farmed rainbow trout. OmpA protein can be used as a subunit vaccine candidate molecule of A. johnsonii.