Homoeologous evolution of the allotetraploid genome of Poa annua L.

Abstract

Abstract Poa annua (annual bluegrass) is an allotetraploid grass and one of the most widely dispersed plant species on earth. Here, we report the chromosome-scale genome assemblies of P. annua’s diploid progenitors, Poa infirma and Poa supina. We find that the diploids diverged from their common ancestor 5.5–6.3 million years ago and hybridized to form P. annua ≤ 50,000 years ago. The diploid genomes are similar in chromosome structure and most notably distinguished by the divergent evolutionary histories of their transposable elements, leading to a 1.7⋅ difference in genome size. We show that P. annua’s smaller (B) subgenome is preferentially accumulating genes and that its genes are more highly expressed. Whole-genome resequencing of several additional P. annua ecotypes revealed large-scale chromosomal rearrangements characterized by extensive TE-downsizing and evidence supporting the Genome Balance Hypothesis. The findings and genomic resources presented here will enable the development of homoeolog-specific markers for accelerated weed science and turfgrass breeding.