New insights into mitochondrial segregation from the Doubly Uniparental Inheritance system in bivalves

Area of Science:

• Cell Biology
• Genetics
• Evolutionary Biology

Background:

• Mechanisms of mitochondrial partitioning are not fully understood, yet failures can lead to developmental issues and mutations.
• Doubly Uniparental Inheritance (DUI) in bivalves provides a model system to study mitochondrial segregation.
• In bivalve DUI, sperm mitochondria are directed to germline precursors in male embryos, a process dependent on maternal egg factors.

Purpose of the Study:

• To identify factors regulating differential mitochondrial segregation in bivalve embryos.
• To distinguish between factors involved in mitochondrial segregation and sex determination using evolutionary analysis.
• To understand the molecular basis of the unique mitochondrial segregation patterns observed in male and female bivalve embryos.

Main Methods:

• RNA sequencing (RNA-Seq) of mussel eggs producing male-biased versus female-biased offspring.
• Analysis of convergent evolutionary rates across DUI bivalve genomes.
• Identification and characterization of differentially transcribed genes and long noncoding RNAs.

Main Results:

• Differentially expressed genes in eggs are linked to mitochondrial dynamics, cytoskeletal organization, and vesicular trafficking.
• Multiple long noncoding RNAs, including those from transposable elements, may regulate maternal factors involved in paternal mitochondrial transport.
• Identification of specific gene expression patterns associated with biased mitochondrial inheritance.

Conclusions:

• A conserved protein-protein interaction network mediating mitochondrial segregation was identified by integrating expression and evolutionary data.
• The study reveals novel factors contributing to organelle segregation in animals.
• General principles of organelle selection in animal development are elucidated.