Are cereal grasses a single genetic system?

Abstract

In 1993, a passionate and provocative call to arms urged cereal researchers to consider the taxon they study as a single genetic system and collaborate with each other. Since then, that group of scientists has seen their discipline blossom. In an attempt to understand what unity of genetic systems means and how the notion was borne out by later research, we survey the progress and prospects of cereal genomics: sequence assemblies, population-scale sequencing, resistance gene cloning and domestication genetics. Gene order may not be as extraordinarily well conserved in the grasses as once thought. Still, several recurring themes have emerged. The same ancestral molecular pathways defining plant architecture have been co-opted in the evolution of different cereal crops. Such genetic convergence as much as cross-fertilization of ideas between cereal geneticists has led to a rich harvest of genes that, it is hoped, will lead to improved varieties.

Figure 1. Simplified tree of the family Poaceae.

The numbers of genera and species were obtained from Soreng et al.. The timescale (million years ago [Mya]) indicates approximate divergence times for subfamilies and the Triticeae tribe according to Gallaher et al.. BOP and PACMAD are the main monophyletic clades used to divide the Poaceae family.

Figure 2. Gene collinearity in the grasses: concept and visualizations.

(a) Early genetics hinted at conserved gene order between the grasses. (b) Genome sequences have borne out that notion at a chromosomal scale. (c) But they have also revealed local rearrangements even between members of the same species. Images were taken from Moore et al., Lovell et al., and Brunner et al.

Figure 3. Time line of cereal genomics.

The upper part shows achievements in cereal genetics and genomics. The technologies that enabled those achievements are listed in the bottom part.