In eukaryotes, we can recognize two kinds of chromosomes, based on the location of the kinetochores. The majority of eukaryotes have monocentric chromosomes, in which kinetochoric activity is concentrated in a single locus. In several unrelated eukaryotic lineages, chromosomes are holocentric, having diffuse centromeric / kinetochoric activity along the length of the chromosome. Whether holocentric chromosomes are derived or ancestral is still under debate. This study uses the phylogenetic tree from Time Tree of Life project, comprising more than 50,000 sampled species, to reconstruct the evolution of holocentry. Asymmetrical two-state Markov (Mk2) models were compared with BiSSE models to assess sensitivity of our conclusions to possible effects of holocentry on lineage diversification rates. Our analyses based on Mk2 and BiSSE models inferred that the rate of transition from holocentric to monocentric chromosomes is two orders of magnitude higher than the reverse direction. The ancestral state of all eukaryotes is ambiguous depending on the model, inferred to be either monocentric (Mk2) or holocentric (BiSSE). Whatever the direction, the multiple transitions and high diversity of centromere organization across the tree of life are what we would expect if there are selective advantages to both chromosome types. Understanding those selective advantages is key to understanding how genetic information is organized and transmitted from one generation to the next, and why these major evolutionary transitions in centromere organization have occurred in the first place.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.
Vol. 41 • No. 3