Conjoint Analysis of SMRT- and Illumina-Based RNA-Sequencing Data of Fenneropenaeus chinensis Provides Insight Into Sex-Biased Expression Genes Involved in Sexual Dimorphism

Molecular cloning, characterization, and expression analysis of a sex-biased transcriptional factor sox9 gene of mud crab Scylla paramamosain

Sox9 gene, a crucial member of the Sox gene family, is present in various organisms and involved in many physiological processes, especially in sex determination and gonad development. In this study, we reported a sox9 gene (designated as Spsox9) from Scylla paramamosain through analyzing published gonad transcriptome data. Meanwhile, the accuracy was validated by PCR technology, and the 3' sequences were cloned with 3' RACE technology. The full-length cDNA of Spsox9 is 2843 bp, consisting of a 243 bp 5' UTR, an 1124 bp 3' UTR, and a 1476 bp ORF encoding 491 amino acids. Furthermore, to better understand its conservation among crustacean species, the sox9 gene ortholog was identified in several other crustaceans species with their published transcriptome data, respectively. All of the Sox9 proteins identified in the current study had the common feature of Sox proteins (HMG domain) and were highly conserved among analyzed crustacean species. In all examined tissues, the Spsox9 was mainly expressed in the gonad (testis and ovary), eyestalk, and cerebral ganglion. During embryo development, Spsox9 was highly expressed in 5 pairs of appendages, 7 pairs of appendages, and eye-pigment formation stage. During ovary development, the expression level of Spsox9 remained stable in the first 4 stages (O1-O4) and decreased in the tertiary vitellogenesis (O5) stage. During testis development, the expression level of Spsox9 was highest in the spermatid stage (T2) and was significantly different from that in the spermatocyte stage (T1) and mature sperm stage (T3) (p < 0.05). In addition, Spsox9 exhibited a sex-biased expression pattern in T1 and O1. These present results indicated that the Spsox9 gene might play crucial roles in the gonad and embryo development of mud crab.

QTL mapping and marker identification for sex determination in the ridgetail white prawn, Exopalaemon carinicauda

Sex determination is an important and intriguing research topic in the field of evolutionary and developmental biology. Quantitative trait locus (QTL) mapping for sex is helpful in clarifying the sex determination system of species. In this study, a second high-resolution genetic linkage map was constructed for the ridgetail white prawn, Exopalaemon carinicauda, which included 9280 markers, covering 99.98% of the complete genome. Based on the linkage map, a highly significant sex-related QTL was first mapped to a single linkage group (LG3, LOD > 55.6). Fifty-two markers in the QTL region were significantly associated with sex (p ≤ 10^-40), of which heterogametic genotypes in females supported the ZW sex determination mechanism. Six markers were verified to be significantly associated with sex in the wild population. Some sex-related genes were identified, including phospholipase D, protein kinase shaggy, and longitudinals lacking protein. These results inform our understanding of the mechanisms of sex determination in E. carinicauda.