Asymmetric cell division is a ubiquitous feature during the development of higher organisms. Asymmetry is achieved by differential localization or activities of biological molecules such as proteins, and coding and non-coding RNAs. Here, we present subcellular transcriptomic and proteomic analyses along the animal-vegetal axis of Xenopus laevis eggs. More than 98% of the maternal mRNAs could be categorized into four localization profile groups: animal, vegetal, extremely vegetal, and a newly described group of mRNAs that we call extremely animal, which are mRNAs enriched in the animal cortex region. 3'UTRs of localized mRNAs were analyzed for localization motifs. Several putative motifs were discovered for vegetal and extremely vegetal mRNAs, while no distinct conserved motifs for the extremely animal mRNAs were identified, suggesting different localization mechanisms. Asymmetric profiles were also found for proteins, with correlation to those of corresponding mRNAs. Based on unexpected observation of the profiles of the homoeologous genes exd2 we propose a possible mechanism of genetic evolution.

Department of Chemistry and Biochemistry University of Notre Dame Notre Dame IN 46556 USA

Department of Chemistry Michigan State University East Lansing MI 48824 USA

Institute of Biotechnology of the Czech Academy of Sciences BIOCEV Prumyslova 595 Vestec 252 50 Czech Republic

Institute of Molecular Genetics Videnska 1083 142 20 Prague 4 Czech Republic

TATAA Biocenter Odinsgatan 28 Göteborg 411 03 Sweden

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RNA localization during early development of the axolotl

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NormQ: RNASeq normalization based on RT-qPCR derived size factors