Scientists from France,Germany and Canada have recently put forward a new tree of life based on the most comprehensive phylogenomics study to date ,investigating 128 genes from a total of 55 species – including nine poriferans, eight cnidarians, three ctenophores and the single known species of placozoans. This study was mainly done to overcome the confusions prevailing at the base of the tree of metazoans and also to establish relationships between some of these very early animal groups with a high degree of confidence.
This new study revives traditional views …

Our lab in Ibdml Marseille published a new review article on Hox protein function ,which is currently online and print issue will be released in may ( It also happens to be on the cover of May issue) This review is an effort to better understand molecular mechanism employed by Hox proteins while performing their biological functions. Here my colleagues looked into the sequences of Hox proteins from main evolutionary branches of bilateria, which includes lophotrochozoa (capitella) ,Ecdysozoa (Tribolium) and humans, amphioxus from Deuterostomia. (364)

Hox genes are expressed along the anterior-posterior (A/P) body axis in majority of animals , creating a unique A/P code which plays a pivotal role in segment specific morphogenesis. These homeodomain containing transcription factors are evolutionary conserved at the level of structure ,function and organization. This is best exemplified by their presence in clusters in all animals and provide A/P axial positional information during development.It was the discovery of homeobox in Drosophila and subsequent cloning in Xenopus revealed that the Hox genes that control the antero-posterior (A-P) axis were unexpectedly …

Hox genes are homeodomain containing transcription factors playing a crucial role in patterning the antero-posterior ( AP) axis in bilaterians.The mechanism of patterning by Hox genes is remarkably conserved across the entire bilateria even though huge diversification of body plan exists. The fact that orthologous genes display similar genomic organisation and expression patterns with comparable spatial and temporal characteristics in distantly related species has provided clues for understanding the evolution of the body plan. It was with discovery of homeodomain and later with similarity of Hox clusters in Mice and …

In the previous post we looked into basics of LR asymmetry and why it is important to understand the mechanics governing it. Recent work from the lab of Nipam Patel ,University of California, Berkeley,has shown that the same genes have been responsible for establishing the left-right asymmetry of animals for 500-650 million years, originating in the last common ancestor of all animals with bilateral body organization, creatures that include everything from worms to humans.
As discussed in the first part of this post that despite humans’ superficial symmetry,we are anything but …

Remember Mark Q. Martindale? The evolutionary biologist who surprised us with some astounding results on comb jellies ( Which i have discussed here and here ) ,did it again by adding a new page in the history of anal evolution in metazoans. Acoels ,a bilaterally symmetric triploblastic worms possess a mid-ventral mouth and lack an anus.Morphology and recent molecular phylogenies place the Acoela and the nemertodermatid flatworms as basal branches of the Bilateria. (364)

Trichoplax adherens is the only named (other cryptic species may exists) member of the phylum placozoa and arguably the simplest free-living animals on this planet.Trichoplax are soft-bodied, about 0.5 mm across,made up of four kind of cells (resembling somewhat a large amoeba). The name T. adhaerens was given because it tends to stick to its substrate.
Many people ,including me expected things to become lot simpler regarding nature of placozoans ,once the genome is sequenced.But Trichoplax seems to be in no mood to shed the enigmatic tag attached to it at …