Australia: The Land Where Time Began

A biography of the Australian continent 

Dictyostelium Development – Novel Pattern of Evolutionary Conservation

According to von Baer’s law the most conserved stages of the development of an animal are the early stages. A modified “hourglass” pattern in which an early, though somewhat later stage, is most conserved, has been given support by more recent evidence. The relative complexity of either temporal or spatial interactions have explained both patterns; the time of the most complex interactions is when the highest level of conservation and the lowest level of evolvability occur, as larger effects are caused by these that are more difficult for selection to alter. Tian, Strassmann & Queller¹ suggest it may be the case that this general kind of explanation might apply universally across independent multicellular systems, which is supported by recent findings of the hourglass pattern in pants. In the study reported here RNA-seq expression data obtained from the development of the slime mould Dictyostelium was used to show that it doesn’t follow either of the 2 canonical patters, rather there is a tendency for it to show the strongest conservation and the weakest evolvability late in the development. Tian, Strassmann & Queller¹ propose that this is consistent with a version of the spatial constraints model which has been modified for organisms that never achieve a high degree of developmental modularity.

Sources & Further reading

Tian, X., J. E. Strassmann and D. C. Queller (2013). "Dictyostelium Development Shows a Novel Pattern of Evolutionary Conservation." Molecular Biology and Evolution 30(4): 977-984.