Insights into Sexual Precocity of Female Oriental River Prawn <i>Macrobrachium nipponense</i> through Transcriptome Analysis

<div><p>Background</p><p>The oriental river prawn (<i>Macrobrachium nipponense</i>) is the most prevalent aquaculture species in China. The sexual precocity in this species has received considerable attention in recent years because more and more individuals matured at a small size, which devalues the commercial production. In this study, we developed deep-coverage transcriptomic sequencing data for the ovaries of sexually precocious and normal sexually mature <i>M</i>. <i>nipponense</i> using next-generation RNA sequencing technology and attempted to provide the first insight into the molecular regulatory mechanism of sexual precocity in this species.</p><p>Results</p><p>A total of 63,336 unigenes were produced from the ovarian cDNA libraries of sexually precocious and normal sexually mature <i>M</i>. <i>nipponense</i> using Illumina HiSeq 2500 platform. Through BLASTX searches against the NR, STRING, Pfam, Swissprot and KEGG databases, 15,134 unigenes were annotated, accounting for 23.89% of the total unigenes. 5,195 and 3,227 matched unigenes were categorized by GO and COG analysis respectively. 15,908 unigenes were consequently mapped into 332 KEGG pathways, and many reproduction-related pathways and genes were identified. Moreover, 26,008 SSRs were identified from 18,133 unigenes. 80,529 and 80,516 SNPs were yielded from ovarian libraries of sexually precocious and normal sexually mature prawn, respectively, and 29,851 potential SNPs between these two groups were also predicted. After comparing the ovarian libraries of sexually precocious and normal sexually mature prawn, 549 differentially expressed genes (DEGs) and 9 key DEGs that may be related to sexual precocity of <i>M</i>. <i>nipponense</i> were identified. 20 DEGs were selected for validation by quantitative real-time PCR (QPCR) and 19 DEGs show consistent expression between QPCR and RNAseq-based differential expression analysis datasets.</p><p>Conclusion</p><p>This is the first report on the large-scale RNA sequencing of ovaries of sexually precocious and normal sexually mature <i>M</i>. <i>nipponense</i>. The annotated transcriptome data will provide fundamental support for future research into the reproduction biology of <i>M</i>. <i>nipponense</i>. The large number of candidate SNPs and SSRs detected in this study could be used as genetic markers for population genetics and functional genomics in this species. More importantly, many DEGs, especially nine key DEGs between sexually precocious and normal sexually mature prawns were identified, which will dramatically improve understanding of molecular regulatory mechanism of sexual precocity of this species.</p></div

Statistics of SNP types and positions in the transcriptomes of MNOP when all sequences generated from the MNON transcriptome library were employed as reference sequences.

<p>Statistics of SNP types and positions in the transcriptomes of MNOP when all sequences generated from the MNON transcriptome library were employed as reference sequences.</p

Statistics of SNP types in the transcriptomes of MNOP and MNON when all the consensus assembly sequences generated from the two transcriptome libraries were employed as reference sequences.

<p>Statistics of SNP types in the transcriptomes of MNOP and MNON when all the consensus assembly sequences generated from the two transcriptome libraries were employed as reference sequences.</p

The top twenty most abundant KEGG pathways.

<p>X-axis: distribution of KEGG pathways, Y-axis: the number of sequences mapped into each KEGG pathway.</p

The Venn diagram shows the distribution of unigenes in different databases.

<p>The number of the shared unigenes are in the cross area, while the number of the specific unigenes are in the single area.</p

Length distribution of 63,336 assembled unigenes.

<p>X-axis: Size distribution of assembled unigenes, Y-axis: The number of unigenes in different length range.</p

The top twenty species that match to the sequences of <i>M</i>. <i>nipponense</i>.

<p>The top twenty species that match to the sequences of <i>M</i>. <i>nipponense</i>.</p

Gene ontology (GO) category of the unigenes.

<p>5,195 annotated unigenes were classified into 3 functional categories: molecular_function, biological_process and cellular_component.</p

Medium-Entropy Co–Fe–Cr–Mo Spinel Nanoflowers as Electrocatalysts for Oxygen Evolution

Oxygen evolution reaction (OER) plays an important role in many electrocatalysis-related fields. However, the slow kinetics of the OER seriously hinders energy efficiency. Here, we synthesize flower-like Co–Fe–Cr–Mo medium-entropy spinel (MES) nanosheets on nickel foam (NF) using one-step solvothermal method for the OER. Due to high stability and compositional diversity, the CoFeCrMoOx/NF catalyst exhibits excellent electrocatalytic OER performance with an overpotential of only 196 mV at 10 mA cm–2 in 1.0 M KOH solution, much lower than CoFeCrMnOx/NF, CoFeCrCeOx/NF, CoFeCrSnOx/NF, CoFeCrAlOx/NF, and commercial IrO2 catalysts, reflecting that the formation of flower-like MES has a positive effect on the improvement of OER performance. The introduction of Mo increases active sites, promotes electron transfer, accelerates the adsorption and desorption of the OER intermediates, reduces the energy barrier, and thus improves the performance of the OER. In situ Raman spectra indicate that the surface CoOOH and FeOOH species are important active components for the OER

Positions of single nucleotide polymorphisms (SNPs).

<p><b>A</b> SNP positions in the transcriptomes of MNOP. <b>B</b> SNP position in the transcriptomes of MNON.</p