Advances in Chinese Arctic and subarctic research in marine biology and ecology with emphasis on the Pacific Arctic sector

The Arctic is one of the most sensitive regions that respond through feedback to global climate changes. Climatic, hydrological and ecological changes in the Arctic are clear evidence of global warming. In 2012 and 2014, the 5th and 6th Chinese National Arctic Research Expeditions undertook studies in the Bering Sea, the Arctic Ocean (including the Chukchi Sea), and the Norwegian Sea. These studies provided us with a better understanding of the marine biology and ecology in the Arctic and subarctic regions, particularly in the Pacific Arctic sector. Rapid changes observed in the Arctic environment include the shrinking of cold-water masses in the Bering Sea in the summer, and elevated water temperatures promoting phytoplankton blooms, leading to an increase in phytoplankton transferred to higher trophic levels. As a result, the transfer efficiency of organic matter toward the bottom weakened, leading to a reduction in benthic biomass. This is consistent with expectations that the overall carbon and energy flux will ultimately switch from the dominant mode of sea ice–algae–benthos to one of phytoplankton–zooplankton. Influenced by Pacific water inflow, fluvial runoff and melting sea ice, the Chukchi Sea exhibited different responses to various environmental changes. Interactions between water masses led to other interannual ecological shifts. With the increase in sea ice melt and sunlight in the central region of the Arctic Ocean, the relative abundance of heterotrophic bacteria is expected to increase, and play a vital role in the Arctic microbial loop

The complete mitochondrial genome of the Arctic staghorn sculpin Gymnocanthus tricuspis (Scorpaeniformes: Cottidae)

The complete mitochondrial genome was determined for Arctic staghorn sculpin Gymnocanthus tricuspis (Reinhardt, 1830), which is considered an important part of Arctic food webs. The mitogenome sequence is 16,570 bp in length containing 2 ribosomal RNA genes, 22 tRNA genes, 13 protein-coding genes, and 2 non-coding regions consist of control region (CR) and light-strand replication origin (OL). The overall base composition of the mitogenome was estimated to be A 23.2%, T 29.0%, C 28.8%, and G 19.0%. The complete mitochondrial genome data will provide useful genetic information for future genetic variation identification and genetic diversity evaluation of this important species in Arctic Ocean

Complete mitochondrial genome sequence and phylogenetic analysis of Lycodes polaris (Sabine, 1824)

Lycodes polaris is one of the most widely distributed and abundant eelpout species on the Arctic continental shelves with full mitogenome information unavailable. In this paper, complete mitochondrial genome of L. Polaris was determined with 16,595 bp in length, containing 13 protein-coding genes, 2 ribosomal RNA genes, 22 transfer RNA genes, and 2 non-coding regions (origin of light strand replication and control region). All the protein-coding genes choose ATG as start codon in addition to that COI using GTG. Most genes use TAA or TAG as the stop codon while three others ended with incomplete stop codons. Phylogenetic relationship of L. polaris was also reconstructed. Our result will provide important basis for further studies of L. polaris

Improved Electrical and Thermal Conductivities of Graphene–Carbon Nanotube Composite Film as an Advanced Thermal Interface Material

Thermal management has become a crucial issue for the rapid development of electronic devices, and thermal interface materials (TIMs) play an important role in improving heat dissipation. Recently, carbon−based TIMs, including graphene, reduced graphene oxide, and carbon nanotubes (CNTs) with high thermal conductivity, have attracted great attention. In this work, we provide graphene−carbon nanotube composite films with improved electrical and thermal conductivities. The composite films were prepared from mixed graphene oxide (GO) and CNT solutions and then were thermally reduced at a temperature greater than 2000 K to form a reduced graphene oxide (rGO)/CNT composite film. The added CNTs connect adjacent graphene layers, increase the interlayer interaction, and block the interlayer slipping of graphene layers, thereby improving the electrical conductivity, through−plane thermal conductivity, and mechanical properties of the rGO/CNT composite film at an appropriate CNT concentration. The rGO/CNT(4:1) composite film has the most desired properties with an electrical conductivity of ~2827 S/cm and an in−plane thermal conductivity of ~627 W/(m·K). The produced rGO/CNT composite film as a TIM will significantly improve the heat dissipation capability and has potential applications in thermal management of electronics

Genetic diversity of the yellowfin seabream, Acanthopagrus latus (Actinopterygii: Perciformes: Sparidae)—An enhancement species in Dongshan Bay

Dongshan Bay is located on the west side of the Taiwan Strait, which had abundant fishery resources in the past. With the increase in fishing pressure, resources have declined. To restore the fishery resources in Dongshan Bay and to increase fishing yield, much enhancement and release work has been carried out in Dongshan Bay. The yellowfin seabream, Acanthopagrus latus (Houttuyn, 1782), is an important enhancement species in Dongshan Bay that is also frequently captured. Due to yearly progress in enhancement and release, it is necessary to study the current status of the genetic diversity of yellowfin seabream in Dongshan Bay. The results show that all yellowfin seabream populations have high genetic diversity, which is mainly related to its breeding habits and growth rate, and this ensures a large recruitment stock in the natural seas. The current population has differentiated from the historical population due to a change in genetic structure, and many historical haplotypes have been lost. The results of this study provide a reference for fishery management departments to formulate management measures and conservation policies specifically for yellowfin seabream. In particular, yellowfin seabream is a hermaphroditic and protandrous species. Targeting an older age group as the main fishing subject is not conducive to its breeding protection and resource growth, and therefore, fishing of an older age group should be restricted in fishery production

Genetic characteristics of yellow seabream Acanthopagrus latus (Houttuyn, 1782) (Teleostei: Sparidae) after stock enhancement in southeastern China coastal waters

Yellowfin seabream is an important economic fish that is widely distributed in the East and South China seas. Many attempts to enhance stocks of yellowfin seabream have occurred in China, but a lack of genetic information for this species after stock release represents an obstacle to its management and conservation. To provide scientific guidance for sustainable germplasm resource development, we sequence the mitochondrial DNA (mtDNA) control region (CR) of 123 yellowfin seabream from 6 sample populations (Xiamen, Dongshan I, Dongshan II, Yangjiang, Fangchenggang, and Beibu Gulf). Populations of both wild and cultured yellowfin seabream have high genetic diversity, which we relate to their breeding habits and growth rate. A neighbor-joining tree of CR haplotypes reveals no specific phylogenetic structure corresponding to location of fish capture. Both neutral test and nucleotide mismatch distribution analyses suggest that yellowfin seabream have experienced population expansion events. Pleistocene glacial periods and recent stock releases have played important roles in the formation of present-day phylogeographical patterns. Our study provides baseline information which will assist future research on genetic structure, genetic diversity, and historical demography of yellowfin seabream after stock release in southeast China coastal waters. The use of exotic seeds should be avoided in stock breeding and release, and relevant follow-up surveys and genetic monitoring should be undertaken to clarify the genetic impact of exotic seed use on wild populations

A Small Subunit of Geranylgeranyl Diphosphate Synthase Functions as an Active Regulator of Carotenoid Synthesis in <i>Nicotiana tabacum</i>

As one of the most imperative antioxidants in higher plants, carotenoids serve as accessory pigments to harvest light for photosynthesis and photoprotectors for plants to adapt to high light stress. Here, we report a small subunit (SSU) of geranylgeranyl diphosphate synthase (GGPPS) in Nicotiana tabacum, NtSSU II, which takes part in the regulation carotenoid biosynthesis by forming multiple enzymatic components with NtGGPPS1 and downstream phytoene synthase (NtPSY1). NtSSU II transcript is widely distributed in various tissues and stimulated by low light and high light treatments. The confocal image revealed that NtSSU II was localized in the chloroplast. Bimolecular fluorescence complementation (BiFC) indicated that NtSSU II and NtGGPPS1 formed heterodimers, which were able to interact with phytoene synthase (NtPSY1) to channel GGPP into the carotenoid production. CRISPR/Cas9-induced ntssu II mutant exhibited decreased leaf area and biomass, along with a decline in carotenoid and chlorophyll accumulation. Moreover, the genes involved in carotenoid biosynthesis were also downregulated in transgenic plants of ntssu II mutant. Taken together, the newly identified NtSSU II could form multiple enzymatic components with NtGGPPS1 and NtPSY1 to regulate carotenoid biosynthesis in N. tabacum, in addition to the co-expression of genes in carotenoids biosynthetic pathways

Comparative transcriptome sequencing analysis of female and male Decapterus macrosoma

Sexual growth dimorphism is a common phenomenon in teleost fish and has led to many reproductive strategies. Growth- and sex-related gene research in teleost fish would broaden our understanding of the process. In this study, transcriptome sequencing of shortfin scad Decapterus macrosoma was performed for the first time, and a high-quality reference transcriptome was constructed. After identification and assembly, a total of 58,475 nonredundant unigenes were obtained with an N50 length of 2,266 bp, and 28,174 unigenes were successfully annotated with multiple public databases. BUSCO analysis determined a level of 92.9% completeness for the assembled transcriptome. Gene expression analysis revealed 2,345 differentially expressed genes (DEGs) in the female and male D. macrosoma, 1,150 of which were female-biased DEGs, and 1,195 unigenes were male-biased DEGs. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses showed that the DEGs were mainly involved in biological processes including protein synthesis, growth, rhythmic processes, immune defense, and vitellogenesis. Then, we identified many growth- and sex-related genes, including Igf, Fabps, EF-hand family genes, Zp3, Zp4 and Vg. In addition, a total of 19,573 simple sequence repeats (SSRs) were screened and identified from the transcriptome sequences. The results of this study can provide valuable information on growth- and sex-related genes and facilitate further exploration of the molecular mechanism of sexual growth dimorphism