A ribosomal protein S5 isoform is essential for oogenesis and interacts with distinct RNAs in Drosophila melanogaster

Jian Kong,Hojatollah Vali,Éric Lécuyer,Greco Hernández,Julie Bergalet,Hong Han,Paul Lasko,Louis Philip Benoit Bouvrette,Nam-Sung Moon

doi:10.1038/s41598-019-50357-z

Abstract

In Drosophila melanogaster there are two genes encoding ribosomal protein S5, RpS5a and RpS5b. Here, we demonstrate that RpS5b is required for oogenesis. Females lacking RpS5b produce ovaries with numerous developmental defects that undergo widespread apoptosis in mid-oogenesis. Females lacking germline RpS5a are fully fertile, but germline expression of interfering RNA targeting germline RpS5a in an RpS5b mutant background worsened the RpS5b phenotype and blocked oogenesis before egg chambers form. A broad spectrum of mRNAs co-purified in immunoprecipitations with RpS5a, while RpS5b-associated mRNAs were specifically enriched for GO terms related to mitochondrial electron transport and cellular metabolic processes. Consistent with this, RpS5b mitochondrial fractions are depleted for proteins linked to oxidative phosphorylation and mitochondrial respiration, and RpS5b mitochondria tended to form large clusters and had more heterogeneous morphology than those from controls. We conclude that RpS5b-containing ribosomes preferentially associate with particular mRNAs and serve an essential function in oogenesis.

Highlights

Increasing evidence indicates that ribosomes are heterogeneous and perhaps dynamic, in contrast to the classical view of them as constitutive machinery for protein synthesis[1,2,3,4,5,6,7,8,9,10,11]
Our experiments demonstrate that RpS5b, one of two RpS5 paralogs in Drosophila, is required for completion of oogenesis and for female fertility
While RpS5a is primarily expressed in somatic cells and RpS5b is primarily expressed in germline, we present genetic evidence that both paralogs function in germline in early stages of oogenesis, as germline-specific knockdown of RpS5a exacerbates the RpS5b phenotype, producing a very early arrest in oogenesis

Summary

Introduction

Increasing evidence indicates that ribosomes are heterogeneous and perhaps dynamic, in contrast to the classical view of them as constitutive machinery for protein synthesis[1,2,3,4,5,6,7,8,9,10,11]. RpS5b is upregulated in l(3)mbt brain tumors whose cells are in an undifferentiated state and express many germline-specific genes, of which some have been implicated in tumor growth[17]. These observations suggest that variant ribosomes with different protein composition may be an important factor in establishing or maintaining stem cell and/or germline identity. To investigate this and to explore the role of a variant ribosomal protein in metazoan development, we examined the cellular and developmental functions of Drosophila melanogaster RpS5b

Methods

Results

Conclusion