Phylogeny of evolutionary relationships of sequenced grass genomes. Radiation of grass family, poaceae is dated to have occurred 50-70 million years before present, in line with the date for the pan-grass’ shared ancient whole genome duplication. Soon after the Panicoideae (Zm-Sb) and Ehrhartoideae (Os-Bd) clades diverged, Os and Bd diverged (~49MYA). Zm and Sb diverged ~11MYA, followed immediately by a specific whole genome duplication event in Zm’s lineage. Red stars indicate whole genome duplication events. Expanded genome phylogeny of sequenced grass genomes. Given the pre-grass whole genome duplication event and the Zm specific whole genome duplication event, there are 10 effective genomes for the 4 sequenced grass genomes: 2xBd, 2xOs, 2xSb, 4xZm. Each of these whole genome duplication events contemporaneously creates a duplicate copy of every chromosome and all the underlying genomic features and genes. However, over evolutionary time, many duplicated genes are lost from one homeologous region or its partner through a process known as fractionation. Red stars indicate whole genome duplication events.
The grasses, a family of plants known as the poaceae, can trace their lineages back to a common ancestor that probably lived between 50-70 million years ago, either right before or soon after the extinction of the dinosaurs(dinosaurs didn't eat grass). Since their emergence in the fossil record, the grasses have been extraordinarily successful, becoming one of the largest families of plants on the planet and covering vast swaths of the planet in the form of prairies/savannahs/steppes.
Grasses play a particularly important role in supporting human civilization as either three (rice, wheat, and corn/maize) or four (the same three plus sugar cane) grass species provide more than half of all the calories that feed the worlds population[1], and are the focus of much applied and basic scientific research.
Because of the comparatively recent radiation of the grass species[2], it was possible for us to use synteny to identify genes and genetic regions in grasses with sequenced genomes that are all related by common descent from a single ancestral sequence in the common ancestor of all living grass species.
↑Estimated to be 6.7 billion people as of early 2010
↑Currently (early 2010) most non-grass genomes come from a group of species called the rosids that are estimated to be around twice as old as the grasses
