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The white crucian carp (Carassius auratus cuvieri, WCC) not only is one of the most economically important fish in Asia, characterized by strong reproductive ability and rapid growth rates, but also represents a good germplasm to produce hybrid progenies with heterosis. Gene knockout technique provides a safe and acceptant way for fish breeding. Achieving gene knockout in WCC and its hybrid progeny will be of great importance for both genetic studies and hybridization breeding. Tyrosinase (TYR) is a key enzyme in melanin synthesis. Depletion of tyrin zebrafish and mice results in mosaic pigmentation or total albinism. Here, we successfully used CRISPR-Cas9 to target tyrin WCC and its hybrid progeny (WR) derived from the cross of WCC (♀) and red crucian carp (Carassius auratusred var., RCC, ♂). The level of TYR protein was significantly reduced in mutant WCC. Both the mutant WCC and the mutant WR showed different degrees of melanin reduction compared with the wild-type sibling control fish, resulting from different mutation efficiency ranging from 60% to 90%. In addition, the transcriptional expression profiles of a series of pivotal pigment synthesis genes, i.e. tyrp1, mitfa, mitfb, dctand sox10, were down-regulated in tyr-CRISPR WCC, which ultimately caused a reduction in melanin synthesis. These results demonstrated that tyrplays a key role in melanin synthesis in WCC and WR, and CRISPR-Cas9 is an effective tool for modifying the genome of economical fish. Furthermore, the tyr-CRISPR models could be valuable in understanding fundamental mechanisms of pigment formation in non-model fish.

Hybridization drives rapid speciation by shaping novel genotypic and phenotypic profiles. Genomic incompatibility and transcriptome shock have been observed in hybrids, although this is rarer in animals than in plants. Using the newly sequenced genomes of the blunt snout bream (Megalobrama amblycephala[BSB]) and the topmouth culter (Culter alburnus[TC]), we focused on the sequence variation and gene expression changes in the reciprocal intergeneric hybrid lineages (F1–F3) of BSB × TC. A genome-wide transcriptional analysis identified 145–974 expressed recombinant genes in the successive generations of hybrid fish, suggesting the rapid emergence of allelic variation following hybridization. Some gradual changes of gene expression with additive and dominance effects and various cisand transregulations were observed from F1to F3in the two hybrid lineages. These asymmetric patterns of gene expression represent the alternative strategies for counteracting deleterious effects of the subgenomes and improving adaptability of novel hybrids. Furthermore, we identified positive selection and additive expression patterns in transforming growth factor, beta 1b (tgfb1b), which may account for the morphological variations of the pharyngeal jaw in the two hybrid lineages. Our current findings provide insights into the evolution of vertebrate genomes immediately following hybridization.

A method was proposed to synthesize hollow flower-like NiCo2O4composed of porous nanosheets using a self-template approach. The unique structure is attributed to the synergistic effect of the Kirkendall effect and the Ostwald ripening mechanism. The sheet-like and porous structure endowed the material with a specific surface area of 137.1 m2g−1and a pore volume of 0.418 cm3g−1. The distinctive structure and high-density active sites imparted excellent catalytic performance in oxygen reduction (ORR) and oxygen evolution (OER) reactions. Electrochemical tests showed that the limit current density of ORR reached 5.58 mA cm−2, comparable to that of the noble metal Pt/C (20 wt%). The overpotential of OER at a current density of 10 mA cm−2was only 380 mV, significantly lower than that of the noble metal RuO2. These results indicate that the synthesized hollow flower-like NiCo2O4has the potential to replace noble metals in ORR and OER catalytic applications.

Focusing on adaptation of aquatic organisms, especially fish, can help elucidate complex dynamics in freshwater ecology. The differences in genetic and epigenetic regulation between diploid and triploid Carassius auratusaffect survival under eutrophication. To identify the underlying mechanisms that lead to better adaption of triploids than diploids, we compared mRNA and microRNA (miRNA) expressions in liver tissue of diploid and triploid individuals obtained from the Dongting lake water system in central China. Differential expression analysis revealed that 566 transcripts were significantly up-regulated, whereas 758 were down-regulated in triploids; of these differentially expressed transcripts, 33 transcripts including cacna1d, nfkb2, hspa1and fgfr4were involved in the MAPK signaling pathway, and eight transcripts were determined to be regulated by seven miRNAs. Additionally, four of 25 differential expressed (DE) transcripts (mhc1, irf7, nfkb2and pik3c) involving the viral carcinogenesis pathway were regulated by four miRNAs. Furthermore, genetic polymorphisms analysis showed that more heterozygous mutations were detected in triploids than diploids. The dN/dSresults revealed that 21 genes were under positive selection (dN/dS>1) in C. auratuscomplex. We hypothesize that these changes related to genetic and epigenetic regulation may be caused by abiotic stresses, and facilitate adaptation to environmental changes.

Hybridization can combine the genomes of different strains or species, which leads to changes of genotype and phenotype in the hybrids. In this study, we aimed to investigate the genetic variations of hybrids (WR-F1and WR-F2) derived from the intraspecific hybridization of white crucian carp (Carassius auratus cuvieri, WCC, ♀) and red crucian carp (Carassius auratusred var., RCC, ♂). Here, we compared the orthologous genes in the liver transcriptomes of hybrids with those of WCC and RCC, and classified the orthologous genes into eight gene patterns within three categories (chimera, mutant, and biparental origin genes). The results revealed 19.04%, 4.17% chimeric genes and 6.90%, 5.05% mutations of orthologous genes in WR-F1and WR-F2respectively. Seventeen of twenty-three characterized genes (77%) were confirmed to be the chimeras at the genomic DNA level. The GO classification discovered that some chimeric and mutant genes were related to metabolic process, immune system and developmental process in WR-F1. Our results provide the new evidence that hybridization can combine the parental genomes, leading to changes in the genotype of the resultant hybrids. This is the first report on the formation of chimeric genes from fish intraspecific hybridization, which is potentially interesting from the context of both evolution and the genetic breeding of fish.

Deep-trap persistent luminescent materials, due to their exceptional ability of energy storage and controllable photon release under external stimulation, have attracted considerable attention in the field of optical information storage. Currently, the lack of suitable materials is still the bottleneck that restrains their practical applications. Herein, we successfully synthesized a series of deep-trap persistent luminescent materials Y3Al5–xGaxO12:Ce3+,V3+(x= 0–3) with a garnet structure and developed novel phosphor-in-glass (PiG) films containing these phosphors. The synthesized PiG films exhibited sufficiently deep traps, narrow trap depth distributions, high trap density, high quantum efficiency, and excellent chemical stability, which solved the problem of chemical stability at high temperatures in the reported phosphor-in-silicone films. Moreover, the trap depth in the phosphors and PiG films could be tailored from 1.2 to 1.6 eV, thanks to the bandgap engineering effect, and the emission color was simultaneously changed from green to yellow due to the variation of crystal field strength. Image information was recorded on the PiG films by using a 450 nm blue-light laser in a laser direct writing mode and the recorded information was retrieved under high-temperature thermal stimulation or photostimulation. The Y3Al5–xGaxO12:Ce3+,V3+PiG films as presented in this work are very promising in the applications of multidimensional and rewritable optical information storage.