Gonadal Transcriptome Analysis of Pacific Abalone Haliotis discus discus: Identification of Genes Involved in Germ Cell Development

Abstract

Little is known about the molecular mechanisms governing gonadal developmental processes in abalones. Here, we conducted transcriptome analysis of Pacific abalone Haliotis discus discus for gene discovery in the brain, ovary, testis, and unfertilized eggs. Among the annotated unigenes, 48.6% of unigenes were identified by Venn diagram analysis as having universal or tissue-specific expression. Twenty-three genes with gonad-biased gene ontology (GO) terms were first obtained. Secondly, 36 genes were found by screening known gene names related to germ cell development. Finally, 17 genes were obtained by querying the annotated unigene database for zygotically expressed gonadal genes (ovary and testis) and maternally expressed gonadal genes (ovary, testis, and unfertilized eggs) using keywords related to reproduction. To further verify tissue distribution pattern and subcellular localization of these genes, RT-PCR and in situ hybridization were performed using a unigene encoding a germ cell marker, vasa, as control. The results showed that vasa was expressed mainly in the early developmental stages of germ cells in both sexes. One of the candidate genes, vitelline envelope zona pellucida domain protein 12 (ZP12), was expressed in the primordial germ cells of immature gonad and early developmental stages of germ cells of the adult female. The results obtained from the present study suggest that vasa and ZP12 are involved in germ cell development of Pacific abalone and that ZP12 is an especially useful germ cell-specific marker in immature adults. The current gonadal transcriptome profile is an extensive resource for future reproductive molecular biology studies of this species.

Genomic Evidence for Speciation with Gene Flow in Broadcast Spawning Marine Invertebrates

“…This hypothesis is in line with the result of our phylogenomic analyses. Although it is difficult to estimate the divergence times among the Western Pacific abalones because information on the mutation rates of marine invertebrates is limited, our demographic modeling using the human mutation rate (2.5 × 10 −8 ; Nachman and Crowell 2000 ) suggests that H. gigantea diverged 14 million years ago (Ma) and H. discus and H. madaka diverged 3 Ma assuming generation time of 3 years ( H. discus in the wild reach sexual maturity as 3- or 4-year-olds; Yu et al 2018 ). Fossil records of H. discus and H. gigantea in Pliocene have been reported ( Geiger and Groves 1999 ).…”

Comparative transcriptome analysis of three gonadal development stages reveals potential genes involved in gametogenesis of the fluted giant clam (Tridacna squamosa)

“…Recent research on the sex determination mechanisms and sex-related genes of mollusks has made considerable progress with the advancement of next-generation sequencing technology. However, research efforts have mainly focused on dioecious mollsuks such as Haliotis rufescens (Myosho et al, 2012), Chlamys nobilis [ 32 ] Patinopecten yessoensis [ 33 ] Haliotis discus discus [ 34 ] Crassostrea hongkongensis [ 35 ] Mytilus edulis [ 36 ] and Crassostrea gigas [ 37 ]; studies on hermaphroditic mollusks such as giant clams are extremely scarce. Thus, it’s vital to identify genes that are involved in the gonadal development of hermaphroditic animals.…”

Different metazoan parasites, different transcriptomic responses, with new insights on parasitic castration by digenetic trematodes in the schistosome vector snail Biomphalaria glabrata

“…In our model system, trematodes served as probes to elicit host responses that help to identify for the first time many Biomphalaria genes relevant to their reproduction and that are responsive to parasite manipulation. Although studies of genes involved in gonadogenesis and gametogenesis are in their infancy in molluscs, recent studies in abalones and bivalves draw attention to several groups of molecules that seem to be involved in the sexual maturation process [ 67 , 85 – 88 ]. Many of the genes identified in these studies were also down-regulated in iM line snails at 2 and 8dpi following exposure to S. mansoni and E. paraensei .…”