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Noncanonical expression of caudal during early embryogenesis in the pea aphid Acyrthosiphon pisum: maternal cad-driven posterior development is not conserved

Authors

  • C-c. Chang,

    Corresponding author
    1. Research Center for Developmental Biology and Regenerative Medicine, National Taiwan University, Taipei, Taiwan
    2. Genome and Systems Biology Degree Program, National Taiwan University, Taipei, Taiwan
    • Laboratory for Genetics and Development, Department of Entomology/Institute of Biotechnology, College of Bio-Resources and Agriculture, National Taiwan University, Taipei, Taiwan
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    • Equal contribution.
  • Y-m. Hsiao,

    1. Laboratory for Genetics and Development, Department of Entomology/Institute of Biotechnology, College of Bio-Resources and Agriculture, National Taiwan University, Taipei, Taiwan
    2. Genomics Research Center, Academia Sinica, Taipei, Taiwan
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    • Equal contribution.
  • T-Y. Huang,

    1. Laboratory for Genetics and Development, Department of Entomology/Institute of Biotechnology, College of Bio-Resources and Agriculture, National Taiwan University, Taipei, Taiwan
    2. Institute of Biochemical Sciences, College of Life Science, National Taiwan University, Taipei, Taiwan
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  • C. E. Cook,

    1. EMBL-European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton, UK
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  • S. Shigenobu,

    1. NIBB Core Research Facilities, National Institute for Basic Biology, Okazaki, Japan
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  • T-H. Chang

    1. Genome and Systems Biology Degree Program, National Taiwan University, Taipei, Taiwan
    2. Genomics Research Center, Academia Sinica, Taipei, Taiwan
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Correspondence: Chun-che Chang, Laboratory for Genetics and Development, Department of Entomology, National Taiwan University, no. 27, Lane 113, Roosevelt Road, Sec. 4, Taipei 106, Taiwan. Tel.: +8862 33665578; fax: +8862 27369366; e-mail: chunche@ntu.edu.tw

Abstract

Previously we identified anterior localization of hunchback (Aphb) mRNA in oocytes and early embryos of the parthenogenetic and viviparous pea aphid Acyrthosiphon pisum, suggesting that the breaking of anterior asymmetry in the oocytes leads to the formation of the anterior axis in embryos. In order to study posterior development in the asexual pea aphid, we cloned and analysed the developmental expression of caudal (Apcad), a posterior gene highly conserved in many animal phyla. We found that transcripts of Apcad were not detected in germaria, oocytes and embryos prior to the formation of the blastoderm in the asexual (viviparous) pea aphid. This unusual expression pattern differs from that of the existing insect models, including long- and short-germ insects, where maternal cad mRNA is passed to the early embryos and forms a posterior–anterior gradient. The first detectable Apcad expression occurred in the newly formed primordial germ cells and their adjacent blastodermal cells during late blastulation. From gastrulation onward, and as in other insects, Apcad mRNA is restricted to the posteriormost region of the germ band. Similarly, in the sexual (oviparous) oocytes we were able to identify anterior localization of Aphb mRNA but posterior localization of Apcad was not detected. This suggests that cad-driven posterior development is not conserved during early embryogenesis in asexual and sexual pea aphids.

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