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. 2022 Mar 24:13:868742.
doi: 10.3389/fgene.2022.868742. eCollection 2022.

Full-Length Transcriptome Sequences Provide Insight Into Hermaphroditism of Freshwater Pearl Mussel Hyriopsis schlegelii

Qi Zeng  1   2 , Beijuan Hu  1   2   3 , Andres Hortas Blanco  4 , Wanchang Zhang  1   2 , Daxian Zhao  1   2 , Paulino Martínez  4 , Yijiang Hong  1   2   3
Affiliations

Full-Length Transcriptome Sequences Provide Insight Into Hermaphroditism of Freshwater Pearl Mussel Hyriopsis schlegelii

Qi Zeng et al. Front Genet. .

Abstract

The freshwater mussel Hyriopsis schlegelii is a cultured bivalve in China, and the quality of the pearls produced is affected by the type of gonads. However, because of the lack of a published genome and the complexity of sex determination, research on sex reversal and development of this species is limited. In this study, Illumina RNA-seq and PacBio Isoform Sequencing (Iso-Seq) were combined to analyze the gonads of H. schlegelii. A total of 201,481 high-quality transcripts were generated. The study identified 7,922 differentially expressed genes in three comparison group (females versus males, hermaphrodites versus females, and hermaphrodites versus males). Twenty-four genes were identified as potential sex-related genes, including sox9 and wnt4 involved in sex determination, and vtg, cyp17a1 and 17β-hsd2 involved in gonadal development. We also speculated a possible pathways for the formation of hermaphroditism in H. schlegelii. The data provide a clear view of the transcriptome for H. schlegelii gonads and will be valuable in elucidating the mechanisms of gonad development.

Keywords: 17β-hsd2; Hyriopsis schlegelii; Iso-seq; RNA-seq; gonad.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1
FIGURE 1
Histological characteristics of ovary (A and B), testes (C and D) and hermaphrodite (E and F) from 30-month-old H. schlegelii.; So: Secondary oocyte; Mo: Mature oocyte; St: Spermatoblast; Sp: Sperm; Ss: Secondary spermatocyte; Ps: Primary Spermatocyte; M: Morula structure; Mf: Female follicle; Ff: Male follicle.
FIGURE 2
FIGURE 2
Distribution of nonredundant full-length transcript from the gonad transcriptome of H. schlegelii.
FIGURE 3
FIGURE 3
Annotation of transcripts from H. schlegelii’s gonads. (A) Gene function annotation in 5 databases (Nr, Nt, KOG, KEGG, GO). (B) Homologous species distribution of gonad annotated in the NR database. (C) Annotation of the GO function of the gonadal transcript. (D) Annotation of the KEGG function of the gonadal transcript.
FIGURE 4
FIGURE 4
Prediction of transcription factors, long-non-coding RNAs and SSR of gonadal transcripts. (A) Transcription factor statistic. (B) Venn diagram of the number of lncRNAs predicted by CNCI, CPC, PLEK, and pfam protein structure domain analysis. (C) Prediction of SSR by MISA.
FIGURE 5
FIGURE 5
(A) The cluster heatmap (Log2(FPKM+ 1) values) indicates the expression patterns of deferential expression genes in the three type gonad of H. schlegelii. (B) Venn diagrams describing the numbers of unique and shared differentially expressed genes (DEGs).
FIGURE 6
FIGURE 6
KEGG and GO enrichment analysis (A)GO analysis and KEGG analysis of DEGs under hermaphrodite and female. (B) GO analysis and KEGG analysis of DEGs under hermaphrodite and male. (C) GO analysis and KEGG analysis of DEGs under male and female.
FIGURE 7
FIGURE 7
(A) The circle heatmap showed the expression level of the screened genes related to hermaphroditism. (B)The solid line and dotted line predicted interactions are displayed as gene-gene interactions; The solid line border indicates that the gene has been annotated, and the red solid line border indicates that the gene is a differentially expressed gene. The color blocks around the differentially expressed gene are the expression levels of the gene in the three types of gonads.
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