Limb patterning genes function during bettle horn development and diversification

I believe that the only one that rules the nature is "survival".

The following interesting paper presents evidences that conserved genes can gain new functions during evolution. The insects used in the paper reminds me a wonderful month I spent with my classmates in the summer of 2002, in Tianmu Mountain area. I am also amazed by the fact that RANi has been used so widely that almost any protein in any species can be knockdown now!

Proc Natl Acad Sci U S A. 2009 Jun 2;106(22):8992-8997.

From the Cover: Differential recruitment of limb patterning genes during development and diversification of beetle horns.

Moczek AP, Rose DJ.

Department of Biology, Indiana University, 915 East Third Street, Myers Hall 150, Bloomington, IN 47405-7107.

The origins of novel complex phenotypes represent one of the most fundamental, yet largely unresolved, issues in evolutionary biology. Here we explore the developmental genetic regulation of beetle horns, a class of traits that lacks obvious homology to traits in other insects. Furthermore, beetle horns are remarkably diverse in their expression, including sexual dimorphisms, male dimorphisms, and interspecific differences in location of horn expression. At the same time, beetle horns share aspects of their development with that of more traditional appendages. We used larval RNA interference-mediated gene function analysis of 3 cardinal insect appendage patterning genes,dachshund, homothorax, and Distal-less, to investigate their role in development and diversification of beetle horns within and between species. Transcript depletion of all 3 patterning genes generated phenotypic effects very similar to those documented in previous studies that focused on general insect development. In addition, we found that Distal-less and homothorax, but not dachshund, regulate horn expression in a species-, sex-, body region-, and body size-dependent manner. Our results demonstrate differential co-option of appendage patterning genes during the evolution and radiation of beetle horns. Furthermore, our results illustrate that regulatory genes whose functions are otherwise highly conserved nevertheless retain the capacity to acquire additional functions, and that little phylogenetic distance appears necessary for the evolution of sex- and species-specific differences in these functions.

PMID: 19451631

F1000 review

Artyom Kopp
University of California, United States of America
Developmental Biology

This paper sheds new light on the molecular mechanisms underlying the evolution of novel morphological structures.
The origin of novel traits is one of the most fascinating questions in evolutionary biology. Beetle horns, which are highly diverse and often sexually dimorphic structures, are a clear and charismatic example of evolutionary innovations. The authors show that horn development involves a subset of genes that also play much more ancient, evolutionarily conserved roles in the development of insect legs and other appendages. It appears that part of the limb patterning network was co-opted in the course of evolution to control the development of the new structures.