Aletheia Tamewitz, Lawrence Lab
The Secret Life of Genomes: Revealing Ancient Periodic Motifs That Constrain Gene Transfer
Lateral gene transfer (LGT) is a dominant force in bacterial evolution, mediating the acquisition of novel capabilities. Because genes are not acquired with equal frequency from any donor genome, it is important to elucidate factors which restrict LGT. A gene transfer event can impart benefits, such as a useful function conferred by the encoded protein, which increases its likelihood of retention. However, transfer events will incur detriments if the foreign DNA disrupts the native genomic architecture that enables bacterial cells to maneuver their genomes; this would decrease the likelihood of retention. One candidate for genomic architecture that may restrict LGT is the ~10.5 bp dinucleotide periodicity found in genomes from all domains of life. Here we show that dinucleotide periodicity varies significantly between genomes in a way that may impact LGT. Closely related organisms share similar profiles of periodic sequences, while distantly related organisms are more likely to show different periodicities. We also show that, while the dinucleotides that are periodic become more dissimilar as organisms become more distantly related, there is a core set of dinucleotides that are periodic in all domains of life. We show that this periodicity is under selection, rather than arising from mutational biases alone. Additionally, we show in bacteria that recently acquired regions are more similar in periodicity to their recipient genomes than to random non-recipient genomes. This suggests that dinucleotide periodicity is an ancient, fundamental genomic architecture, the maintenance of which has placed restrictions on how bacteria can evolve.
Friday, May 29, 2020
12PM