Wnt8a is one of the candidate genes that play essential roles in the elongation of the seahorse prehensile tail

Comparative transcriptomic analysis of left-right sensory differences in Haliotis discus hannai

Asymmetric development, in which functional differences occur between left-right symmetrical organs, is widespread in organisms, including fish and mollusks. However, the asymmetry of symmetrical sensory structures in Haliotis discus hannai, a gastropod with a sensitive sensory system, remains unknown. This study analyzed the transcriptomes of three sensory structures (eyestalks, cephalic tentacles, and epipodial tentacles) to explore potential asymmetries in this species. RNA-seq revealed functional differences in sensory ability and sperm-egg recognition between right and left eyestalks, with cephalic tentacles displaying asymmetry in cytoskeletal organization and cell cycle regulation. Epipodial tentacles showed similar asymmetries, including immune response differences. Moreover, the cAMP-protein kinase A (PKA)-CREB-binding protein (CBP) signaling pathway responded asymmetrically, with PKA responding to activators and inhibitors on both sides and CBP showing a stronger response on the right. These findings provide insights into sensory asymmetry in mollusks and guidance for further investigations of the molecular mechanisms underlying asymmetry in symmetrical organs.

Potential roles of the sirtuins in promoting longevity for larger Argopecten scallops

Annual bay scallops are commercially significant bivalve species for fisheries and aquaculture, but their small size and severe inbreeding depression impede the development of their industry. Some interspecific hybrids of bay scallops and peruvian scallops show longer lifespans and significantly greater sizes, which may result from the longevity genes in the latter (7-10 years). Sirtuins (SIRTs) play pivotal roles in the genetic control of aging in various model species and human beings. However, the role of SIRTs in longevity has not been systematically studied in aquatic animals. In this study, different gene numbers, sequences, structures and tandem duplications of SIRTs were first identified between the two scallops through genome-wide analysis. Cloning and characteristics of the SIRT1 and SIRT6 ORFs revealed dramatic variations in amino acids between the two scallops, which may cause intrinsic differences in function for longevity regulation. In particular, the amino acid variations in the N-terminus may auto-regulate conformations, causing intrinsic differences in catalytic activity for longevity regulation. The robust expression of SIRT1 and SIRT6-2 in peruvian scallops suggested they may exert a role in extending the lifespan. Nutrient restriction (NR) could promote lifespan in terrestrial model organisms, and the SIRTs and their related genes responded to NR for longevity in scallops; peruvian scallops showed a higher ability of autophagy. This study provides potential biomarkers for breeding long-lived larger scallop hybrids for the sustainability of aquaculture. Moreover, the genetic variation during evolution in the two scallops provides a foundation for further research on the longevity function of the SIRTs.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42995-024-00269-3.

Gene expression patterns and DNA methylation of neuron and pancreatic β-cell developments in zebrafish embryos treated with bisphenol F and AF

Bisphenol F (BPF) and bisphenol AF (BPAF) are structural analogues of bisphenol A (BPA) that are used in the manufacture of a myriad of BPA-free products; however, there is a paucity of information regarding their developmental effects. The present study investigates the effects of BPF and BPAF on neurodevelopment and pancreatic β-cell differentiation via altering DNA methylation and gene expression patterns using the zebrafish model. BPF and BPAF induced behavioral perturbations: increased average speed, increased maximum acceleration, increased mania time and decreased static time, in 0.3 and 1.0 μM groups in zebrafish embryos. Glucose level was significantly increased in 1.0 μM BPF (28 %); while a monotonic increase of 29 %, 55 %, and 74 % were observed in 0.1, 0.3, and 1.0 μM BPAF, respectively. Consistent with a decreased insulin mRNA level, the expression of two critical transcription factors (pdx-1 and foxa2) essential for the development and functioning of beta-cells decreased following the bisphenols exposure. In addition, embryonic exposure to BPF and BPAF upregulated the transcription of developmental genes (vegfa, wnt8a, and mstn1) and neuron-related genes (mbp, elavl3, gap43, gfap). Also, the expressions of DNA methyltransferases (dnmt1, dnmt3, dnmt4, dnmt5, dnmt6, dnmt7, and dnmt8) were significantly aberrant compared with the control group. The Bisulfite PCR results indicate increased DNA methylation at promoter regions of pdx-1 in BPF (8.2 %) and BPAF (7.6 %); α1-tubulin in BPF (5.3 %) and in BPAF (4.1 %), congruous with the increased dnmt1 and dnmt3 transcription, at early stage of zebrafish development. The present study indicates that zebrafish embryonic exposure to BPF and BPAF elicits islet dysfunction and neuron perturbations resulting in increased DNA methylation levels.

Asymmetric evolution of ISG15 homologs and the immune adaptation to LBUSV infection in spotted seabass (Lateolabrax maculatus)

The battle between host and viral is ubiquitous across all ecosystems. Despite this, research is scarce on the antiviral characteristics of fish, particularly in those that primarily rely on innate immune responses. This study, comprehensively explored the genetic and antiviral features of ISG15 in spotted seabass, focusing on its response to largemouth bass ulcerative syndrome virus (LBUSV). Through whole-genome BLAST and PCR cloning, two ISG15 homologs, namely LmISG15a and LmISG15b, were identified in spotted seabass, both encoding highly conserved proteins. However, a distinctive contrast emerged in their expression patterns, with LmISG15a exhibiting high expression in immune organs while LmISG15b remained largely silent across various organs. Regulatory elements analysis indicated an asymmetric evolution of the two ISG15s, with the minimal expression of LmISG15b may attribute to the loss of a necessary ISRE and an additional instability "ATTTA" motif. Association analysis demonstrated a significant correlation between LmISG15a expression and LBUSV infection. Subsequent antiviral activity detection revealed that LmISG15a interacted with LBUSV, inhibiting its replication by activating ISGylation and downstream pro-inflammatory mediators. In summary, this study unveils a distinct evolutionary strategy of fish antiviral gene ISG15 and delineates its kinetic characteristics in response to LBUSV infection.

Deciphering the origin of developmental stability: The role of intracellular expression variability in evolutionary conservation

Progress in evolutionary developmental biology (evo-devo) has deepened our understanding of how intrinsic properties of embryogenesis, along with natural selection and population genetics, shape phenotypic diversity. A focal point of recent empirical and theoretical research is the idea that highly developmentally stable phenotypes are more conserved in evolution. Previously, we demonstrated that in Japanese medaka (Oryzias latipes), embryonic stages and genes with high stability, estimated through whole-embryo RNA-seq, are highly conserved in subsequent generations. However, the precise origin of the stability of gene expression levels evaluated at the whole-embryo level remained unclear. Such stability could be attributed to two distinct sources: stable intracellular expression levels or spatially stable expression patterns. Here we demonstrate that stability observed in whole-embryo RNA-seq can be attributed to stability at the cellular level (low variability in gene expression at the cellular levels). We quantified the intercellular variations in expression levels and spatial gene expression patterns for seven key genes involved in patterning dorsoventral and rostrocaudal regions during early development in medaka. We evaluated intracellular variability by counting transcripts and found its significant correlation with variation observed in whole-embryo RNA-seq data. Conversely, variation in spatial gene expression patterns, assessed through intraindividual left-right asymmetry, showed no correlation. Given the previously reported correlation between stability and conservation of expression levels throughout embryogenesis, our findings suggest a potential general trend: the stability or instability of developmental systems-and the consequent evolutionary diversity-may be primarily anchored in intrinsic fundamental elements such as the variability of intracellular states.

Gene loss and co-option of toll-like receptors facilitate paternal immunological adaptation in the brood pouch of pregnant male seahorses

Male pregnancy in syngnathids (seahorses, pipefishes, and sea dragons) is an evolutionary innovation in the animal kingdom. Paternal immune resistance to the fetus is a critical challenge, particularly in seahorses with fully enclosed brood pouches and sophisticated placentas. In this study, comparative genomic analysis revealed that all syngnathid species lost three vertebrate-conserved Toll-like receptors (TLR1, TLR2, and TLR9), of which all play essential roles in immune protection and immune tolerance in the uterus and placenta. Quantitative real-time PCR (qRT-PCR) analysis showed that the TLR paralog genes including TLR18, TLR25, and TLR21 were highly expressed in the placenta inside the seahorse brood pouch and changed dynamically during the breeding cycle, suggesting the potentially important role of the TLRs during male pregnancy. Furthermore, the immune challenge test in vitro showed a remarkable expression response from all three TLR genes to specific pathogenic antigens, confirming their immune function in seahorse brood pouches. Notably, the altered antigen recognition spectrum of these genes appeared to functionally compensate in part for the lost TLRs, in contrast to that observed in other species. Therefore, we suggest that gene loss and co-option of TLRs may be a typical evolutionary strategy for facilitating paternal immunological adaptation during male pregnancy.

Hepcidin Gene Co-Option Balancing Paternal Immune Protection and Male Pregnancy

Viviparity has originated independently more than 150 times in vertebrates, while the male pregnancy only emerged in Syngnathidae fishes, such as seahorses. The typical male pregnancy seahorses have closed sophisticated brood pouch that act as both uterus and placenta, representing an excellent model system for studying the evolutionary process of paternal immune protection. Phylogenetic analysis indicated that the hampII gene family has multiple tandem duplicated genes and shows independent lineage-specific expansion in seahorses, and they had the highest ratio of nonsynonymous substitutions to synonymous substitutions (dN/dS) in the seahorse phylogenetic branch. The expression levels of hampIIs in the brood pouch placenta were significantly higher during pregnancy than non-pregnancy. Both LPS stimulation test in vivo and cytotoxicity test in vitro proved the immunological protection function of hampIIs against pathogen infection in seahorse. Besides, seahorse hampII peptides exhibit weaker antibacterial function, but stronger agglutination and free endotoxin inhibition. We assumed that the modified immunological function seemed to be a trade-off between the resistance to microbial attack and offspring protection. In brief, this study suggests that the rapid co-option of hampIIs contributes to the evolutionary adaption to paternal immune care during male pregnancy.