voltarData: 01/11/2018
Título: A birth-and-death account of the similarity distribution of homologous gene pairs in plants resulting from recurrent whole genome doubling, fractionation and speciation
Palestrante: David Sankoff, Universidade de Ottawa, Canadá.
Data: 1 de novembro de 2018, 14:00 h.
Local: Instituto de Computação, campus Praia Vermelha, UFF.
Resumo: An important type of evidence in analyzing ancient polyploidization events is the distribution of coding sequence similarities between two paralogous genes in a genome. For flowering plants with one, two, or more whole genome doubling (WGD) events in their history, the distribution of similarities is a mixture of distributions, each component of which is centered at a similarity value indicative of the age of one of the events. We present a birth-and-death model for predicting the shape of these distributions based on the event times, the ploidy multiplicities of the events, rates of loss of duplicate genes from the genome (fractionation), and rates of sequence divergence. The process has one biologically-motivated constraint, which is mathematically tractable and whose parameters are well suited to statistical inference. We then provide a treatment of the transition from one genome to two daughter genomes that smoothly continues the fractionation regime in place before speciation, and extends it independently in each of these species until a new WGD in that species or until the present time of observation. With some additional details, this solution enables a complete model encompassing all the WGD in the ancestral genome, the speciation event, and all the independent WGDs in the daughter genomes. It defines all the homolog pairs at the time of observation in terms of the event at which they originated.
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