Identification of multifunctionality of the PmE74 gene and development of SNPs associated with low salt tolerance in Penaeus monodon

Effects of molting on the expression of ecdysteroid responsive genes in the crustacean molting gland (Y-organ)

Ecdysteroid molting hormones coordinate arthropod growth and development. Binding of 20-hydroxyecdysone (20E) to ecdysteroid receptor EcR/RXR activates a cascade of nuclear receptor transcription factors that mediate tissue responses to hormone. Insect ecdysteroid responsive and Forkhead box class O (FOXO) transcription factor gene sequences were used to extract orthologs from blackback land crab (Gecarcinus lateralis) Y-organ (YO) transcriptome: Gl-Ecdysone Receptor (EcR), Gl-Broad Complex (Br-C), Gl-E74, Gl-Hormone Receptor 3 (HR3), Gl-Hormone Receptor 4 (HR4), Gl-FOXO, and Gl-Fushi tarazu factor-1 (Ftz-f1). Quantitative polymerase chain reaction quantified mRNA levels in tissues from intermolt animals and in YO of animals induced to molt by multiple limb autotomy (MLA) or eyestalk ablation (ESA). Gl-EcR, Gl-Retinoid X Receptor (RXR), Gl-Br-C, Gl-HR3, Gl-HR4, Gl-E74, Gl-E75, Gl-Ftz-f1, and Gl-FOXO were expressed in all 10 tissues, with Gl-Br-C, Gl-E74, Gl-E75, and Gl-HR4 mRNA levels in the YO lower than those in most of the other tissues. In MLA animals, molting had no effect on Gl-Br-C, Gl-E74, and Gl-Ftz-f1 mRNA levels and little effect on Gl-EcR, Gl-E75, and Gl-HR4 mRNA levels. Gl-HR3 and Gl-FOXO mRNA levels were increased during premolt stages, while Gl-RXR mRNA level was highest during intermolt and premolt stages and lowest at postmolt stage. In ESA animals, YO mRNA levels were not correlated with hemolymph ecdysteroid titers. ESA had no effect on Gl-EcR, Gl-E74, Gl-HR3, Gl-HR4, Gl-Ftz-f1, and Gl-FOXO mRNA levels, while Gl-RXR, Gl-Br-C, and Gl-E75 mRNA levels were decreased at 3 days post-ESA. These data suggest that transcriptional up-regulation of Gl-FOXO and Gl-HR3 contributes to increased YO ecdysteroidogenesis during premolt. By contrast, transcriptional regulation of ecdysteroid responsive genes and ecdysteroidogenesis were uncoupled in the YO of ESA animals.

Studies on the Relationships between Growth and Gonad Development during First Sexual Maturation of Macrobrachium nipponense and Associated SNPs Screening

In this study, we used full-sib families to investigate the association between growth and gonad development during first sexual maturation of M. nipponense. We found that male GSI was significantly negatively correlated with growth traits (p < 0.01) and there were no significant correlations between female GSI (Gonadosomatic index) and growth traits (p > 0.05). HSI (Hepatopancreas index) in both males and females showed no significant correlations with growth traits (p > 0.05). We furthermore investigated the association between the specific allele of Mn-CTS L1 polymorphism and gonad development and growth traits. In total, 35 mutation loci were screened and 16 high-quality single-nucleotide polymorphisms (SNPs) loci were obtained after validation. Four and two SNPs proved to be strongly associated with all growth traits in female and male M. nipponense separately, among which A+118T might be a candidate SNP positively associated with large growth traits. Two and one SNPs were screened, respectively, in males and females to associate with GSI, while three SNPs were detected to associate with female HSI, among which A+1379C may be applied as a potential molecular marker for gene-assisted selection to improve both reproduction speed and growth traits in M. nipponense.

Responses of population structure and genomic diversity to climate change and fishing pressure in a pelagic fish

The responses of marine species to environmental changes and anthropogenic pressures (e.g., fishing) interact with ecological and evolutionary processes that are not well understood. Knowledge of changes in the distribution range and genetic diversity of species and their populations into the future is essential for the conservation and sustainable management of resources. Almaco jack (Seriola rivoliana) is a pelagic fish with high importance to fisheries and aquaculture in the Pacific Ocean. In this study, we assessed contemporary genomic diversity and structure in loci that are putatively under selection (outlier loci) and determined their potential functions. Using a combination of genotype-environment association, spatial distribution models, and demogenetic simulations, we modeled the effects of climate change (under three different RCP scenarios) and fishing pressure on the species' geographic distribution and genomic diversity and structure to 2050 and 2100. Our results show that most of the outlier loci identified were related to biological and metabolic processes that may be associated with temperature and salinity. The contemporary genomic structure showed three populations-two in the Eastern Pacific (Cabo San Lucas and Eastern Pacific) and one in the Central Pacific (Hawaii). Future projections suggest a loss of suitable habitat and potential range contractions for most scenarios, while fishing pressure decreased population connectivity. Our results suggest that future climate change scenarios and fishing pressure will affect the genomic structure and genotypic composition of S. rivoliana and lead to loss of genomic diversity in populations distributed in the eastern-central Pacific Ocean, which could have profound effects on fisheries that depend on this resource.

Transcriptome and molecular regulatory mechanisms analysis of gills in the black tiger shrimp Penaeus monodon under chronic low-salinity stress

Background: Salinity is one of the main influencing factors in the culture environment and is extremely important for the survival, growth, development and reproduction of aquatic animals. Methods: In this study, a comparative transcriptome analysis (maintained for 45 days in three different salinities, 30 psu (HC group), 18 psu (MC group) and 3 psu (LC group)) was performed by high-throughput sequencing of economically cultured Penaeus monodon. P. monodon gill tissues from each treatment were collected for RNA-seq analysis to identify potential genes and pathways in response to low salinity stress. Results: A total of 64,475 unigenes were annotated in this study. There were 1,140 upregulated genes and 1,531 downregulated genes observed in the LC vs. HC group and 1,000 upregulated genes and 1,062 downregulated genes observed in the MC vs. HC group. In the LC vs. HC group, 583 DEGs significantly mapped to 37 signaling pathways, such as the NOD-like receptor signaling pathway, Toll-like receptor signaling pathway, and PI3K-Akt signaling pathway; in the MC vs. HC group, 444 DEGs significantly mapped to 28 signaling pathways, such as the MAPK signaling pathway, Hippo signaling pathway and calcium signaling pathway. These pathways were significantly associated mainly with signal transduction, immunity and metabolism. Conclusions: These results suggest that low salinity stress may affect regulatory mechanisms such as metabolism, immunity, and signal transduction in addition to osmolarity in P. monodon. The greater the difference in salinity, the more significant the difference in genes. This study provides some guidance for understanding the low-salt domestication culture of P. monodon.