miR-34 regulates reproduction by inhibiting the expression of MIH, CHH, EcR, and FAMeT genes in mud crab Scylla paramamosain

Whole transcriptome RNA sequencing provides novel insights into the molecular dynamics of ovarian development in mud crab, Scylla paramamosain after mating

Ovarian development in animals is a complicated biological process, requiring the simultaneous coordination among various genes and pathways. To understand the dynamic changes and molecular regulatory mechanisms of ovarian development in mud crab (Scylla paramamosain), both histological observation and whole transcriptome sequencing of ovarian tissues at different mating stages were implemented in this study. The histological results revealed that ovarian development was delayed in unmated females (60 days after courtship behavior but not mating), who exhibited an oocyte diameter of 56.38 ± 15.17 μm. Conversely, mated females exhibited accelerated the ovarian maturation process, with females reaching ovarian stage III (proliferative stage) 23 days after mating and attained an average oocyte diameter of 132.19 ± 15.07 μm. Thus, mating process is essential in promoting the rapid ovarian development in mud crab. Based on the whole transcriptome sequencing analysis, a total of 518 mRNAs, 1502 lncRNAs, 18 circRNAs and 151 miRNAs were identified to be differentially expressed between ovarian tissues at different mating stages. Notably, six differentially expressed genes (DEGs) associated with ovarian development were identified, including ovary development-related protein, red pigment concentrating hormone receptor, G2/mitotic-specific cyclin-B3-like, lutropin-chorio gonadotropic hormone receptor, renin receptor, and SoxB2. More importantly, both DEGs and targets of differentially expressed non-coding RNAs (DEncRNAs) were enriched in renin-angiotensin system, TGF-β signaling, cell adhesion molecules, MAPK signaling pathway, and ECM-receptor interaction, suggesting that these pathways may play significant roles in the ovarian development of mud crabs. Moreover, competition endogenous RNA (ceRNA) networks were constructed while mRNAs were differentially expressed between mating stages were involved in Gene Ontology (GO) biological processes such as developmental process, reproduction, and growth. These findings could provide solid foundations for the future development of female mud crab maturation enhancement strategy, and improve the understanding of the ovarian maturation process in crustaceans.

The miRNAs let-7b and miR-141 Coordinately Regulate Vitellogenesis by Modulating Methyl Farnesoate Degradation in the Swimming Crab Portunus trituberculatus

Methyl farnesoate (MF), a crucial sesquiterpenoid hormone, plays a pivotal role in the reproduction of female crustaceans, particularly in the vitellogenesis process. Despite extensive research on its functions, the molecular mechanisms that regulate MF levels during the vitellogenic phase remain largely elusive. This study investigates the roles of microRNAs (miRNAs), significant post-transcriptional regulators of gene expression, in controlling MF levels in the swimming crab Portunus trituberculatus. Through bioinformatic analysis, four miRNAs were identified as potential regulators targeting two genes encoding Carboxylesterases (CXEs), which are key enzymes in MF degradation. Dual luciferase reporter assays revealed that let-7b and miR-141 suppress CXE1 and CXE2 expression by directly binding to their 3' UTRs. In vivo overexpression of let-7b and miR-141 significantly diminished CXE1 and CXE2 levels, consequently elevating hemolymph MF and enhancing vitellogenin expression. Spatiotemporal expression profile analysis showed that these two miRNAs and their targets exhibited generally opposite patterns during ovarian development. These findings demonstrate that let-7b and miR-141 collaboratively modulate MF levels by targeting CXEs, thus influencing vitellogenesis in P. trituberculatus. Additionally, we found that the expression of let-7b and miR-141 were suppressed by MF, constituting a regulatory loop for the regulation of MF levels. The findings contribute novel insights into miRNA-mediated ovarian development regulation in crustaceans and offer valuable information for developing innovative reproduction manipulation techniques for P. trituberculatus.

Regulation of vtg and VtgR in mud crab Scylla paramamosain by miR-34

BACKGROUND

Vitellogenin (Vtg) is the precursor of major yolk protein and plays a crucial role in the maturation of oocytes and the production of eggs in oviparous animals. Vitellogenin receptor (VtgR) mediates the transport of Vtg explicitly to oocytes in the membrane. In a previous study, we found that miR-34 can regulate the expression of some eyestalk genes and affect reproduction in mud crab Scylla paramamosain, one of the most important economic crabs on the coasts of southern China.

METHODS AND RESULTS

In this study, firstly, we found that miR-34 can target at 3'-UTR of Vtg and VtgR genes by using bioinformatic tools and predicted miR-34 might depress the expression of Vtg and VtgR. Secondly, the relative luciferase activity of HEK293T cells co-transfected with miRNA mimic and pmir-RB-REPORTTM-Vtg/VtgR-3'UTR was significantly lower than those of cells co-transfected with mimic NC and pmir-RB-REPORTTM-Vtg/VtgR-3'UTR. Finally, in vivo experiments showed that agomiR-34 could repress the expression of Vtg and VtgR genes, while Antigomir-34 could promote the expression of these two genes.

CONCLUSIONS

These results confirm our hypothesis and previous published results that miR-34 may indirectly regulate ovarian development by binding to the 3'-UTR of Vtg and VtgR genes and inhibiting their expression.

miR-9 and miR-263 Regulate the Key Genes of the ERK Pathway in the Ovary of Mud Crab Scylla paramamosain

Mud crab Scylla paramamosain is one of the most important economic crabs in China. The molecular regulatory mechanism of ovarian development has received considerable attention in recent years. Some studies found that ERK (extracellular signal-regulated protein kinase) signaling pathway plays an important role in ovarian development and is negatively regulated by microRNAs (miRNAs). However, the study about the regulation of miRNA on the ERK pathway in crustacean's ovary remains unknown. In this study, the target genes of the ERK signaling pathway regulated by selected miRNAs identified from the ovary of mud crab in our previous research were predicted by using bioinformatics tools. The results showed that the ERK2 might be a target gene of miR-9c, miR-263a, and miR-263b; MEK2 may be a target gene of miR-263a; and Rap-1b may be a target gene of miR-9, miR-9c, and miR-263a. Results of in vitro dual-luciferase reporter assay showed that the relative luciferase activities were significantly lower in HEK293T cells co-transfected with the combination of miRNA mimics and pmir-RB-REPORTTM-target gene-3'UTR than those with the combination of mimics NC and pmir-RB-REPORTTM-target gene-3'UTR. In contrast, the relative luciferase activities were significantly higher in HEK293T cells co-transfected with miRNA inhibitor than those with inhibitor NC. To further validate in vitro results, the miRNA reagents were injected into the living female mud crabs, and the expression levels of miRNAs and target genes after the injection were analyzed by quantitative real-time PCR. The in vivo experimental results showed that miRNAs (miR-9c/miR-263a) agomir (enhancers)/antagomir (inhibitors) can enhance/decrease the expression of two miRNAs, respectively, and the expression of target genes in the ovary was declined/increased after injection of agomir/antagomir reagent. In conclusion, miR-9/miR-263 can negatively regulate the expression of the ERK pathway genes (ERK2, MEK2, and Rap-1b) in the ovary of mud crab.

Characterization and expression profile of farnesoic acid O-methyltransferase gene from Indian white shrimp, Penaeus indicus

Methyl farnesoate (MF), a sesquiterpenoid synthesized in the mandibular organ, regulates many physiological processes in crustaceans including growth and reproduction. In the present study, farnesoic acid O-methyltransferase (FAMeT), the key enzyme responsible for final step conversion of farnesoic acid (FA) to methyl farnesoate (MF), was cloned and characterized from the nervous tissues of Penaeus indicus. Multiple sequence alignment, prediction of conserved domain regions, phosphorylation sites identification and phylogenetic analysis indicated that putative FAMeT fragment from P. indicus (PiFAMeT), shares a high degree of sequence identity to FAMeT proteins isolated from other crustaceans species. Quantitative real-time PCR analysis revealed ubiquitous expression of PiFAMeT in all the tissues examined, with comparative higher mRNA levels in nervous tissue and ovary. Additionally, the levels of PiFAMeT also showed gradual increase of expression correlating with the advancement in ovarian maturation. Further to support their role in promoting ovarian development, serotonin treatment (5HT, 50 μg/g body weight) was given to eyestalk intact and unilaterally eyestalk ablated females which resulted in significant increase in PiFAMeT transcript levels at day 7 and day 14. The relatively higher levels of PiFAMeT, reflecting higher levels of MF, suggest a role during secondary vitellogenesis thereby regulating ovarian development in P. indicus. Further research is required to understand the synergistic interaction of MF pathways with serotonergic and other regulatory pathways in regulating ovarian maturation in penaeid shrimps.