Development Genes and Evolution

, Volume 217, Issue 6, pp 421–433 | Cite as

Segmental expression of Pax3/7 and Engrailed homologs in tardigrade development

  • Willow N. Gabriel
  • Bob GoldsteinEmail author
Original Article


How morphological diversity arises through evolution of gene sequence is a major question in biology. In Drosophila, the genetic basis for body patterning and morphological segmentation has been studied intensively. It is clear that some of the genes in the Drosophila segmentation program are functioning similarly in certain other taxa, although many questions remain about when these gene functions arose and which taxa use these genes similarly to establish diverse body plans. Tardigrades are an outgroup to arthropods in the Ecdysozoa and, as such, can provide insight into how gene functions have evolved among the arthropods and their close relatives. We developed immunostaining methods for tardigrade embryos, and we used cross-reactive antibodies to investigate the expression of homologs of the pair-rule gene paired (Pax3/7) and the segment polarity gene engrailed in the tardigrade Hypsibius dujardini. We find that in H. dujardini embryos, Pax3/7 protein localizes not in a pair-rule pattern but in a segmentally iterated pattern, after the segments are established, in regions of the embryo where neurons later arise. Engrailed protein localizes in the posterior ectoderm of each segment before ectodermal segmentation is apparent. Together with previous results from others, our data support the conclusions that the pair-rule function of Pax3/7 is specific to the arthropods, that some of the ancient functions of Pax3/7 and Engrailed in ancestral bilaterians may have been in neurogenesis, and that Engrailed may have a function in establishing morphological boundaries between segments that is conserved at least among the Panarthropoda.


Engrailed Pax3/7 Ecdysozoa Segmentation Development 



We thank Greg Wray, Nipam Patel, and members of the Goldstein lab for discussions and comments on the manuscript and Nipam Patel for generously sharing cross-reactive antibodies. This work was funded by NSF grant IBN-0235658 to BG.

Supplementary material (5.5 mb)
Supplementary file 1 Confocal stack of Pax3/7 stained embryo at the stage when there are approximately 40 nuclei with Pax3/7 localization in the developing head region. Green is Pax3/7, and purple is DNA. Film starts from the head region (MOV 5 mb) (82.7 mb)
Supplementary file 2 Confocal stack of Pax3/7 stained embryo at the stage when there are approximately 60 nuclei with Pax3/7 localization in the developing head region. Green is Pax3/7, and purple is DNA. Film starts from the head region (MOV 86 mb) (29.1 mb)
Supplementary file 3 Confocal stack of a lateral view of an Engrailed stained embryo at the stage when Engrailed localizes to stripes of cells at the posterior of each ectodermal segment. Green is Pax3/7, and purple is DNA (MOV 30 mb)
427_2007_152_Fig1_ESM.gif (289 kb)
Supplementary file 4

Individual confocal sections of the Pax3/7 stained embryo in S1. Anteriormost sections are upper left (GIF 295 kb)

427_2007_152_Fig1_ESM.tif (13.3 mb)
High resolution image file (TIF 13 kb)
427_2007_152_Fig2_ESM.gif (517 kb)
Supplementary file 5

Individual confocal sections of the Pax3/7 stained embryo in S2. Anteriormost sections are upper left (GIF 529 kb)

427_2007_152_Fig2_ESM.tif (26.6 mb)
High resolution image file (TIF 27 mb)
427_2007_152_Fig3_ESM.gif (376 kb)
Supplementary file 6

Individual confocal sections of the Engrailed stained embryo in S3. Left-most side of embryo sections are upper left (GIF 385 kb)

427_2007_152_Fig3_ESM.tif (31.5 mb)
High resolution image file (TIF 33 mb)
Supplementary file 7

Film of complete z-stack of DAPI-stained embryo just as endomesodermal pouches are forming. A–P and D–V are labeled in the film. Yellow arrowheads point to the four pouches that are visible in the embryo at this time. The two posterior-most pouches are completely enclosed, and the two anterior-most pouches are incompletely enclosed in this embryo (MOV 756 kb)


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Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  1. 1.Biology DepartmentUniversity of North Carolina at Chapel HillChapel HillUSA

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