Hox genes pattern the anterior-posterior axis of the juvenile but not the larva in a maximally indirect developing invertebrate, Micrura alaskensis NemerteaReportar como inadecuado

Hox genes pattern the anterior-posterior axis of the juvenile but not the larva in a maximally indirect developing invertebrate, Micrura alaskensis Nemertea - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

BMC Biology

, 13:23

First Online: 11 April 2015Received: 05 November 2014Accepted: 20 March 2015DOI: 10.1186-s12915-015-0133-5

Cite this article as: Hiebert, L.S. & Maslakova, S.A. BMC Biol 2015 13: 23. doi:10.1186-s12915-015-0133-5


BackgroundThe pilidium larva is a novel body plan that arose within a single clade in the phylum Nemertea - the Pilidiophora. While the sister clade of the Pilidiophora and the basal nemerteans develop directly, pilidiophorans have a long-lived planktotrophic larva with a body plan distinctly different from that of the juvenile. Uniquely, the pilidiophoran juvenile develops inside the larva from several discrete rudiments. The orientation of the juvenile with respect to the larval body varies within the Pilidiophora, which suggests that the larval and juvenile anteroposterior AP axes are patterned differently. In order to gain insight into the evolutionary origins of the pilidium larva and the mechanisms underlying this implied axial uncoupling, we examined the expression of the Hox genes during development of the pilidiophoran Micrura alaskensis.

ResultsWe identified sequences of nine Hox genes and the ParaHox gene caudal through a combination of transcriptome analysis and molecular cloning, and determined their expression pattern during development using in situ hybridization in whole-mounted larvae. We found that Hox genes are first expressed long after the pilidium is fully formed and functional. The Hox genes are expressed in apparently overlapping domains along the AP axis of the developing juvenile in a subset of the rudiments that give rise to the juvenile trunk. Hox genes are not expressed in the larval body at any stage of development.

ConclusionsWhile the Hox genes pattern the juvenile pilidiophoran, the pilidial body, which appears to be an evolutionary novelty, must be patterned by some mechanism other than the Hox genes. Although the pilidiophoran juvenile develops from separate rudiments with no obvious relationship to the embryonic formation of the larva, the Hox genes appear to exhibit canonical expression along the juvenile AP axis. This suggests that the Hox patterning system can maintain conserved function even when widely decoupled from early polarity established in the egg.

KeywordsBiphasic life cycle Hox Indirect development Larval evolution Nemertea Pilidium Electronic supplementary materialThe online version of this article doi:10.1186-s12915-015-0133-5 contains supplementary material, which is available to authorized users.

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Autor: Laurel S Hiebert - Svetlana A Maslakova

Fuente: https://link.springer.com/

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