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ABSTRACT. The swimming crab, Portunus trituberculatus, is an important marine animal and is widely cultured in China. In the present study, suppression subtractive hybridization was applied to identify the differentially expressed genes in the ovaries of mature and immature P. trituberculatus. One hundred and seventy six expressed sequence tag (ESTs) were identified, of which 100 were down-regulated, and 76 up-regulated. BLAST analysis identified 51 unigenes, of which 27 were down-regulated, and 24 up-regulated. Quantitative real-time reverse transcriptase polymerase chain reaction results indicated that the SSH technique is valuable in screening genes related to ovarian development. Genes identified in this study encoded proteins corresponding to a wide range of functions and included immune response protein, transcription initiation factor, metabolic proteins, chromosome, histone h3, ovarian development-related protein, and vitellogenin. In addition, 64 metabolic pathways were annotated in differentially expressed ESTs by using the Kyoto Encyclopedia of Genes and Genomes pathway. Four annotated pathways (oxidative phosphorylation, carbon metabolism, fatty acid degradation, and protein digestion and absorption) appeared to be involved in ovarian development. In ontology analysis, 5.83% of the cellular process genes in reverse subtraction cDNA library are involved in reproduction, and 5.88% involved in developmental process. In up-regulated genes, myosin II-expressed polehole-like protein; histone h3; ovigerous-hair stripping substance; peritrophin 48; and ovarian development-related protein appeared to be involved in ovarian development. Identification of differentially expressed genes in the mature and immature ovary of the swimming crab provides new insights for further studies on the mechanism underlying ovarian development in this species.

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Rapid, specific, and on-site detection of virulent foodborne pathogenic strains plays a key role in controlling food safety. In this work, an ultrasensitive and specific Phage@DNAzyme signal probe was designed to detect foodborne pathogens. The proposed sensing probe was composed of the selected phage and functionalized DNAzyme, which realized the specific recognition of target foodborne pathogens at the strain level and the efficient catalysis of copper­(II) based azide-alkyne cycloaddition (CuAAC) click reaction with fluorescent signal, respectively. As a proof of concept, the virulent Escherichia coli O157:H7 (E. coli O157:H7) as the representative analyte was first enriched and purified from the complex food samples by a 4-mercaptophenylboronic acid-modified gold slide. Following, the Phage@DNAzyme probes were specifically combined with the captured E. coli O157: H7 and catalyzed the click reaction between 3-azido-7-hydroxycoumarin and 3-butyn-1-ol with the assistance of Cu­(II) to generate a visual fluorescent signal. Finally, the corresponding fluorescent signals were measured by a smartphone to quantify the target concentrations. Under optimized conditions, the bioassay exhibited a wide linear range from 102 to 108 CFU/mL and the detection limit was 50 CFU/mL (S/N = 3). It was further extended to the detection of another foodborne pathogen Salmonella typhimurium with satisfying sensing performances. This work gives a new path for developing rapid, specific, and on-site detection methods for trace levels of pathogenic strains in foods.