Biodiversity is more than meets the eye

Fig. 8. Schematics of wild-type and Blimp1 mutant embryos. (photo credit: Science Advances)

written by: Pick lab
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Visible features of organismal body plans are often highly conserved within large taxa. For example, different species of birds have wings and beaks. For insects, segmentation is a shared and defining feature of the body plan.  Screens in the model insect Drosophila previously identified genes responsible for the development of body segments and one might have thought that different insects would all utilize the same genes, given that they all are segmented. In a paper published from the Pick lab in Science Advances, Reding et al. show that this is not the case: different insects use different genes to achieve the same outcome – formation of body segments. Studying the milkweed bug, Oncopeltus fasciatus, graduate student Katie Reding undertook a challenging screen to ask if novel genes control segmentation in this species. Collaborating with scientists at the Institute for Genome Science, University of Maryland School of Medicine, she analyzed the sequences of genes expressed at time points during embryonic development when segmentation is established. She then analyzed the expression patterns of over 50 of these genes and identified one, Blimp1, expressed in a pattern expected for a role in segmentation. She followed this with RNA interference experiments that suggested a role for Blimp1 in generating segments. To stringently test Blimp1’ s function, Katie used CRISPR/Cas9 genome editing, a technique she had previously developed in the Pick lab, to generate a mutation in the newly identified gene. This mutation showed a Drosophila-like segmentation phenotype, although Blimp1 is not required for segmentation in Drosophila. This exciting result demonstrated genetic diversity underlying the highly conserved feature of segmentation in insects: during evolution, regulatory genes have changed function dramatically but without any impact on phenotype or morphology. Thus, organisms are even more diverse than their phenotypes show us: even for a shared feature, the genes controlling it may be wholly different in different species - an invisible layer of biodiversity in animal systems. 

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