Integrated Proteomic and Transcriptomic Analysis of Gonads Reveal Disruption of Germ Cell Proliferation and Division, and Energy Storage in Glycogen in Sterile Triploid Pacific Oysters (Crassostrea gigas)

Chen Chen,Hong Yu,Qi Li

doi:10.3390/cells10102668

Abstract

Triploid oysters have poor gonadal development, which can not only bring higher economic benefits but also have a potential application in the genetic containment of aquaculture. However, the key factors that influence germ cell development in triploid oysters remain unclear. In this study, data-independent acquisition coupled to transcriptomics was applied to identify genes/proteins related to sterility in triploid Crassostrea gigas. Eighty-four genes were differentially expressed at both the protein and mRNA levels between fertile and sterile females. For male oysters, 207 genes were differentially expressed in the transcriptomic and proteomic analysis. A large proportion of downregulated genes were related to cell division, which may hinder germ cell proliferation and cause apoptosis. In sterile triploid females, a primary cause of sterility may be downregulation in the expression levels of certain mitotic cell cycle-related genes. In sterile triploid males, downregulation of genes related to cell cycle and sperm motility indicated that the disruption of mitosis or meiosis and flagella defects may be linked with the blocking of spermatogenesis. Additionally, the genes upregulated in sterile oysters were mainly associated with the biosynthesis of glycogen and fat, suggesting that sterility in triploids stimulates the synthesis of glycogen and energy conservation in gonad tissue.

Highlights

IntroductionTriploids possess three sets of chromosomes in somatic cells instead of two in normal diploids
Our results indicate that a primary cause of sterility in female triploid oysters may be the alteration in the expression levels of certain mitotic cell cycle-related genes/proteins
We first performed integrated proteomics and transcriptomics in the gonad among diploid and triploid Pacific oysters and excavated genes/proteins related to the gonadal sterility of triploids

Summary

Introduction

Triploids possess three sets of chromosomes in somatic cells instead of two in normal diploids. The odd number of homologous chromosomes may cause unequal separation during meiosis, resulting in retarded gonadal development or aneuploid gametes. Triploids can occur across all major animal groups but are often lethal in some vertebrates, such as birds and mammals. It is easy to cause dead embryos or lethal abnormalities [2,3], which makes triploids are less common in the wild, whereas in fishes, amphibians, and lizards [4,5,6], triploids may develop and display relatively normal phenotypes. In many aquaculture organisms, such as fishes, shrimps, and shellfishes, triploids are viable but tend to be sterile due to a lack of gonadal development. The sterility can allow for faster growth rates as the energy invested in reproduction can be diverted to somatic growth [7,8]

Methods

Discussion

Conclusion