"The notion that Hox genes can simply acquire new responsibilities quickly, especially without compromising old ones, is rather novel," Moczek said. "This is one of relatively few examples that show that this indeed occurs in animal evolution." What Stansbury and Moczek found by down-regulating the function of each of these two genes was that both were required for proper adult photic organ formation.
"In particular, the Abd-B Hox gene was critical to all aspects of photic organ formation, suggesting it has evolved novel lantern-specific regulatory interactions," Moczek said.
They also found that Abd-B repressed abdominal pigmentation in fireflies' photic organs, thereby creating a translucent cuticle that allows the light to escape the body interior. In addition, the sixth and seventh abdominal segments of most insects is ordinarily under the sole purview of abd-A rather than Abd-B. However, it is precisely these segments that house the lantern in fireflies, suggesting the possibility of an anterior expansion of the domain of Abd-B function. That's a big deal because Hox genes, given their hugely important functions in establishing the basic body plan, normally confine themselves to strict and highly conserved boundaries of expression.
"This is just the beginning," Moczek said. "We want to know what are the target genes with which abd-A and Abd-B interact to form the organ; we want to get data on exactly when and where a given gene product is active; and we want to learn more about how the adult organ evolved from the larval organ, a much simpler structure located on yet another segment," he added.
Moczek is no stranger to investigating novel traits, and the new work presents another example within his body of work that the possibility exists that Hox-gene mediated innovation -- true, unique innovation -- is more widespread than generally th
|Contact: Steve Chaplin|