Paternal RNA contributions in the C. elegans zygote. Caenorhabditis elegans

Development of the early embryo is thought to be mainly driven by maternal gene products and post-transcriptional gene regulation. Here, we used metabolic labeling to show that RNA can be transferred by sperm into the embryo. To identify genes with paternal expression in the embryo, we performed crosses of males and females from divergent C. elegans strains. RNA sequencing of mRNAs and small RNAs in the 1-cell hybrid embryo revealed that about two hundred paternal mRNAs are reproducibly expressed in the embryo, and that about half of assayed endogenous siRNAs and piRNAs are also of paternal origin. Together, our results suggest an unexplored paternal contribution to early development. Overall design: To reveal the identity of paternal RNA molecules, we performed a cross of males and females from two divergent C. elegans strains because we reasoned that sequencing of embryonic RNA and SNP analysis should then identify and quantify maternal and paternal transcripts. These sequencing experiments were carried out in purified hybrid 1-cell embryos and comprised small RNAs and mRNAs. For comparison we sequenced mRNAs and small RNAs from the parental strains: paternal (Hawaiian males, CB4856) and maternal (fem-1(hc17ts)/TX189(OMA-1::GFP). For the annotation of strain specific mutations (SNPs) we sequenced mRNA and small RNAs extracted from whole worms. All experiments were performed in at least two independent biological replicates.