Comparative Transcriptome Analysis of Hepatopancreas Reveals Sexual Dimorphic Response to Methyl Farnesoate Injection in Litopenaeus vannamei

Abstract

Sexually dimorphic traits such as growth and body size are often found in various crustaceans. Methyl farnesoate (MF), the main active form of sesquiterpenoid hormone in crustaceans, plays vital roles in the regulation of their molting and reproduction. However, understanding on the sex differences in their hormonal regulation is limited. Here, we carried out a comprehensive investigation on sexual dimorphic responses to MF in the hepatopancreas of the most dominant aquacultural crustacean-the white-leg shrimp (Litopenaeus vannamei). Through comparative transcriptomic analysis of the main MF target tissue (hepatopancreas) from both female and male L. vannamei, two sets of sex-specific and four sets of sex-dose-specific differentially expressed transcripts (DETs) were identified after different doses of MF injection. Functional analysis of DETs showed that the male-specific DETs were mainly related to sugar and lipid metabolism, of which multiple chitinases were significantly up-regulated. In contrast, the female-specific DETs were mainly related to miRNA processing and immune responses. Further co-expression network analysis revealed 8 sex-specific response modules and 55 key regulatory transcripts, of which several key transcripts of genes related to energy metabolism and immune responses were identified, such as arginine kinase, tropomyosin, elongation of very long chain fatty acids protein 6, thioredoxin reductase, cysteine dioxygenase, lysosomal acid lipase, estradiol 17-beta-dehydrogenase 8, and sodium/potassium-transporting ATPase subunit alpha. Altogether, our study demonstrates the sex differences in the hormonal regulatory networks of L. vannamei, providing new insights into the molecular basis of MF regulatory mechanisms and sex dimorphism in prawn aquaculture.

Keywords: Litopenaeus vannamei; hormonal regulation; methyl farnesoate; sex dimorphism; transcriptome.

Figure 1

Composite volcano plot showing the DETs in hepatopancreases of different MF injection groups compared to their own control group. The red and green dots represent the up- and the down-regulated transcripts with |Log2FC| > 1.5 and p-value < 0.05. The top 10 annotated DETs based on |Log2FC| values are labeled.

Figure 2

The clustering result of DETs profile determined by Log2FC values. The right bar charts show the numbers of the up- (red) and down-regulated (blue) DETs of different groups in corresponding clusters. The left line charts show the average value of Log2FC values in clusters. The heatmap represents the expression profile determined by Log2FC values, and the hierarchical clustering was performed with the “mfuzz” method in R package ClusterGVis [27]. The numbers in the color blocks represent the number of transcripts in each cluster. C1–C6, the six clusters of DETs.

Figure 3

KEGG pathway enrichment of DETs in C1–C6 clusters.

Figure 4

Sexual dimorphic co-expression modules responding to sesquiterpenoid hormone. (A) Co-expression networks of the female-specific responding modules. (B) Co-expression networks of the male-specific responding modules. (C) Co-expression networks of the female–dose-specific responding modules. (D) Co-expression networks of the male–dose-specific responding modules. Circle color corresponds to module color. Triangles represent male-specific transcripts. The annotated transcripts were labeled, while the ones without annotation were labeled with “-”. The key DETs in the module were marked in red.

Figure 4

Sexual dimorphic co-expression modules responding to sesquiterpenoid hormone. (A) Co-expression networks of the female-specific responding modules. (B) Co-expression networks of the male-specific responding modules. (C) Co-expression networks of the female–dose-specific responding modules. (D) Co-expression networks of the male–dose-specific responding modules. Circle color corresponds to module color. Triangles represent male-specific transcripts. The annotated transcripts were labeled, while the ones without annotation were labeled with “-”. The key DETs in the module were marked in red.