Investigating Conserved Function of Male and Female Developmental Genes in a Model Bivalve

Bivalves, such as mussels, oysters, and clams, belong to the second most diverse animal phylum. They play a critical role in coastal ecosystems, help maintain water quality, and are widely used in aquaculture. Despite their importance, many developmental processes are not well understood in bivalves.

Several genes have been identified to be correlated with male and female specification and development; however, their exact role is not yet known. The goal of this project is to characterize these genes in bivalve development and identify their roles in the process of differentiating male and female reproductive organs. Our methods involve documenting levels of in gene expression in different tissues and experimentally lowering their expression level to observe changes in development.

This project will provide critical insight into the process of male and female specification and differentiation of reproductive organs. Our project will also help to increase opportunities for students that have obligations outside of the classroom that hinder their ability to pursue a STEM degrees. Research shows that online laboratory courses, especially those that include “Do it yourself” (DIY) kits and manuals, can be as effective as in person labs and decrease barriers for students that have difficulty devoting time to in person laboratory courses.

This project aims to create a completely online DIY laboratory in marine biology and physiology that will act as a model for increasing accessibility to STEM labs and broaden participation.

Although some hypothetical models have been proposed for mechanisms underlying male and female specific gonadal development in mollusks, there have been very few experimental tests of gene function in this process. Using phylotranscriptomics, we have identified several putative gonadal development genes in bivalves, including a mollusk specific DMRT gene: DMRT1L.

The primary objective of our proposed project is to characterize the role of putative gonadal development genes in a model, gonochoristic, adult bivalve, the blue mussel M. edulis through two specific aims: (1) Determine the temporal and tissue-specific expression patterns of male and female gonadal development genes using RT-qPCR and in situ hybridization in relation to gametogenesis. (2) Evaluate changes in gonadal development in males and females following knockdown of key gonadal development genes using RNAi (SoxH, DMRT1L, FoxL2, β-catenin). These genes have been studied in bivalves; however, this work has relied on correlations in gene expression between males and females and knowledge gained from distantly related species.

The proposed work will verify the roles of these putative male and female developmental genes and will enable us to develop a transcript-based gonadal development pathway for bivalves. This proposed work will be transformative to understanding the relationships between male and female development pathways across distantly related metazoan species and how they evolved.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.