It has been demonstrated that the sekelsky mothers against decapentaplegic homolog 3 (Smad3) plays an important role in the growth and development of vertebrates. However, little is known about the association between the Smad3 gene and the growth traits of mollusks. In this study, Smad3 from the hard clam Meretrix meretrix (Mm-Smad3) was cloned, characterized, and screened for growth-related single nucleotide polymorphisms (SNPs) in its exons. The full-length cDNA of Mm-Smad3 was 1938 bp, encoding a protein with 428 amino acid residues. The protein sequence included an MH1 (27–135 aa) and MH2 domain (233–404 aa). Promoter analysis showed that the promoter sequence of Mm-Smad3 was 2548 bp, and the binding sites of Pit-1a, Antp, Hb, and other transcription factors are related to the growth and development of hard clams. The phylogenetic tree was divided into two major clusters, including mollusks and vertebrate. The expression level of Mm-Smad3 was predominantly detected in the mantle and foot, while extremely less expression was observed in the digestive gland. The low expression level of Mm-Smad3 was detected at the stages of unfertilized mature eggs, fertilized eggs, four-cell embryos, blastula, gastrulae, trochophore, and D-shaped larvae, whereas an opposite trend was observed regarding the highest expression at the umbo larvae stage (p < 0.05). In the mantle repair experiment, the time-course expression profiles showed that compared to the expression level at 0 h, Mm-Smad3 significantly decreased at 6 h (p < 0.05) but increased at 12 and 48 h. Further, the association analysis identified 11 SNPs in the exons of Mm-Smad3, of which three loci (c.597 C > T, c.660 C > T, c.792 A > T) were significantly related to the growth traits of clam (p < 0.05). Overall, our findings indicated that Mm-Smad3 is a growth-related gene and the detected SNP sites provide growth-related markers for molecular marker-assisted breeding of this species.
Animal hemoglobins(Hbs) not only have function of oxygen carrying capacity,but also include oxidase activity activity,peroxidase activity and antibiosis et al.The structure and function of animal Hbs are of diversity,especially in invertebrate Hbs because of its low conservation,but all Hbs have the function of oxygen carrying capacity.Studies show that the new functions of Hbs can be developed from structural changes.The research on structure and function of Hbs has remained as a focal point in relevant studies on the evolution of Hbs.In this paper,the research progresses are reviewed on the structure,functions and the evolution of Hbs in animals.
Increasing evidence indicates that microbes colonized in early life stages have a long-term effect on animal wellbeing in later life stages. Related research is still limited in aquatic animals, particularly in bivalve mollusks. In this study, we analyzed the dynamics of the bacterial composition of the pelagic larval stages (fertilized egg, trochophore, D-stage, veliger, and pediveliger) and the sessile postlarval stage (spat) of Kumamoto oyster (Crassostrea sikamea) and their relationships with the rearing water bacterioplankton in a hatchery by using Illumina sequencing of bacterial 16S rRNA gene. Both bacterioplankton and larval bacterial communities changed greatly over larval development, and the two communities remarkably differed (r = 0.956, P < 0.001), as highlighted by the differences in the dominant taxa and bacterial diversity. Ecological processes of larval bacterial communities were measured by abundance-unweighted and abundance-weighted standardized effect sizes of the mean nearest taxon distance (ses.MNTD). The unweighted ses.MNTD analysis revealed that the deterministic process constrained the larval bacterial assembly, whereas the weighted ses.MNTD analysis showed that larval bacterial composition was initially governed by stochasticity and then gradually by determinism in the later stages. SourceTracker analysis revealed that the larval bacteria were primarily derived from an internal source, mainly from larvae at the present stage. Additionally, the abundances of larval bacterial-mediated functional pathways that were involved in the amino acid, energy, lipid and carbohydrate metabolisms significantly altered with the larval development. These findings suggest that bacteria assemble into distinct communities in larvae and rearing water in the hatchery system, and the dynamics of bacterial community composition in larvae is likely associated with larval developmental stages.
Allozyme variation within five natural populations of Coelomactra antiquata from Jiaonan Shandong province (JN),Nantong Jiangsu province (NT),Taizhou Zhejiang province,(TZ),Fuzhou Fujian province(FZ), Beihai Guangxi province (BH) were investigated by vertical polyacrylamide gel electrophoresis. Thirteen isozymes in three different tissues (foot,mantle and liver) of Coelomactra antiquata were analyzed and compared. At last, choose liver as allozyme experiment's tissue. Seventeen loci of eight enzyme systems were detected and used for estimating population genetic diversity. The percentages of polymorphic loci in JN,NT,TZ,FZ and BH populations were 58. 82% ,70. 59% ,50. 00% ,56. 25% and 41. 17% ,respectively. The mean effective numbers of allele were 1. 550,1. 555,1. 434,1. 602 and 1. 828,respectively. The mean heterozygosities observed were 0. 240, 0. 270,0. 239,0. 243 and 0. 288,respectively. It means that the genetic variations were BH NT FZ JN TZ, the genetic diversity was high and germ plasma were good in five populations of Coelomactra antiquata. The heterozygous deficiency was common in all populations except for the TZ population. Based on the allozymic variation data,a UPGMA dendrogram was conducted in five populations.
Increasing evidence has revealed accumulated ammonia will cause adverse effects on the growth, reproduction, and survival of aquatic animals. As a marine benthic mollusk, the razor clam Sinonovacula constricta shows better growth and survival under high ammonia nitrogen environment. However, little is known about its adaptation mechanisms to high ammonia stress in an integrated mariculture system. In this study, we analyzed the association between the polymorphism of glutamate dehydrogenase gene ( GDH ), a key gene involved in ammonia nitrogen detoxification, and ammonia tolerance. The results showed that 26 and 22 single-nucleotide polymorphisms (SNPs) of GDH in S. constricta (denoted as Sc-GDH ) were identified from two geographical populations, respectively. Among them, two SNPs (c.323T > C and c.620C > T) exhibited a significant and strong association with ammonia tolerance, suggesting that Sc-GDH gene could serve as a potential genetic marker for molecular marker–assisted selection to increase survival rate and production of S. constricta . To observe the histological morphology and explore the histocellular localization of Sc-GDH, by paraffin section and hematoxylin–eosin staining, the gills were divided into gill filament (contains columnar and flattened cells) and gill cilia, whereas hepatopancreas was made up of individual hepatocytes. The results of immunohistochemistry indicated that the columnar cells of gill filaments and the endothelial cells of hepatocytes were the major sites for Sc-GDH secretion. Under ammonia stress (180 mg/L), the expression levels of Sc-GDH were extremely significantly downregulated at 24, 48, 72, and 96 h ( P < 0.01) after RNA interference. Thus, we can speculate that Sc-GDH gene may play an important role in the defense process against ammonia stress. Overall, these findings laid a foundation for further research on the adaptive mechanisms to ammonia–nitrogen tolerance for S. constricta .
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