Comparative proteomics elucidates the dynamics of ovarian development in the Chinese mitten crab Eriocheir sinensis.

Ovarian development is a complex physiological process for crustacean reproduction that is divided into the oogonium proliferation stage, endogenous vitellogenic stage, exogenous vitellogenic stage, and oocyte maturation stage. Proteomics analysis offers a feasible approach to reveal the proteins involved in the complex physiological processes of any organism. Therefore, this study performed a comparative proteomics analysis of the ovary and hepatopancreas at three key ovarian stages, including stages I (oogonium proliferation), II (endogenous vitellogenesis) and IV (exogenous vitellogenesis), of the Chinese mitten crab Eriocheir sinensis using a label-free quantitative approach. The results showed that a total of 2,224 proteins were identified, and some key proteins related to ovarian development and nutrition metabolism were differentially expressed. The 26 key proteins were mainly involved in the ubiquitin/proteasome pathway (UPP), cyclic AMP-protein kinase A (cAMP-PKA) signaling pathway, and mitogen-activated protein kinase (MAPK) signaling pathway during oogenesis. Fifteen differentially abundant proteins (DAPs) were found to participate in vitellogenesis and oocyte development, such as vitelline membrane outer layer protein 1 homolog, vitellogenin, vitellogenin receptor, heat shock 70 kDa protein cognate 3 and farnesyl pyrophosphate synthase. Forty-seven DAPs related to nutrition metabolism were identified, including the protein digestion, fatty acid metabolism, prostaglandin metabolism, lipid digestion and transportation, i.e. short-chain specific acyl-CoA dehydrogenase, acyl-CoA desaturase, fatty acid-binding protein, long-chain fatty acid CoA ligase 4, and hematopoietic prostaglandin D synthase. These results not only indicate proteins involved in ovarian development and nutrient deposition but also enhance the understanding of the regulatory pathways and physiological processes of crustacean ovarian development.

Genetic diversity and population structure of native mitten crab (Eriocheir sensu stricto) by microsatellite markers and mitochondrial COI gene sequence.

Mitten crab (Eriocheir sensu stricto) is an indigenous and economically important species in East Asia. The genetic diversity and population structure of four wild native Eriocheir s. s. populations, from Yangtze (YZ), Oujiang (OJ), Minjiang (MJ), and Nanliujiang (NLJ) River basin, were studied. Genetic diversity of the four populations was evaluated by eight microsatellite and mitochondrial cytochrome oxidase subunits I (COI) markers. The polymorphism information content (PIC) values ranged from 0.7827 to 0.8580 and Shannon Wiener index (I) values varied from 2.0722 to 2.4088 respectively, according to microsatellite markers analysis. The haplotype diversity (h) values ranged from 0.52101 to 0.87097, while the values of nucleotide diversity (π) varied from 0.00139 to 0.02796 based on mitochondrial COI gene sequence. Four wild Eriocheir s. s. populations all showed high genetic diversity. As microsatellite analysis results, pair-wise FST values of YZ, OJ, MJ and NLJ populations were 0.1347, 0.1103 and 0.0943 respectively, which indicated that they were in medium genetic differentiation (0.05 < FST < 0.15). This was consistent with mitochondrial COI gene's conclusion. The bottleneck analysis was a hint that Eriocheir s. s. experienced bottleneck effect under SMM models of Sign Test and Wilcoxon Sign-rank Test. Based on genetic structure, YZ, OJ and MJ populations were in the same cluster separated from NLJ population. In summary, by microsatellite and mitochondrial COI markers analysis, all four Eriocheir s. s. populations had high genetic diversity, and genetic differentiation was consistent with geographical distance. Populations OJ and MJ were closer to population YZ genetically, and they had large genetic distance with NLJ population. This study provides a particularly important basis for mitten crab resources conservation and utilization in south China.

A second generation SNP and SSR integrated linkage map and QTL mapping for the Chinese mitten crab Eriocheir sinensis.

The Chinese mitten crab Eriocheir sinensis is the most economically important cultivated crab species in China, and its genome has a high number of chromosomes (2n = 146). To obtain sufficient markers for construction of a dense genetic map for this species, we employed the recently developed specific-locus amplified fragment sequencing (SLAF-seq) method for large-scale SNPs screening and genotyping in a F1 full-sib family of 149 individuals. SLAF-seq generated 127,677 polymorphic SNP markers, of which 20,803 valid markers were assigned into five segregation types and were used together with previous SSR markers for linkage map construction. The final integrated genetic map included 17,680 SNP and 629 SSR markers on the 73 linkage groups (LG), and spanned 14,894.9 cM with an average marker interval of 0.81 cM. QTL mapping localized three significant growth-related QTL to a 1.2 cM region in LG53 as well as 146 sex-linked markers in LG48. Genome-wide QTL-association analysis further identified four growth-related QTL genes named LNX2, PAK2, FMRFamide and octopamine receptors. These genes are involved in a variety of different signaling pathways including cell proliferation and growth. The map and SNP markers described here will be a valuable resource for the E. sinensis genome project and selective breeding programs.