Two steps on the path to maize adaptation

Authors: Holland, Jim - Jim

Submitted to: Current Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/18/2018
Publication Date: 9/24/2018
Citation: Holland, J.B. 2018. Two steps on the path to maize adaptation. Current Biology. 28(18):PR1098-R1101.

Interpretive Summary: A new paper published in Current Biology demonstrates that two distinct natural mutations in a gene called ‘ZCN8’ that is known to affect flowering time in corn were selected for during the spread of corn from its center of origin in Southern Mexico to its current range of cultivation in northern USA and Canada. This brief article explains the background and importance of this new finding for general biology readers.

Technical Abstract: Two distinct variations in the promoter of a key flowering time gene were selected during the spread of maize from its tropical origin to northern North America. Maize was domesticated from the wild tropical grass teosinte around 9000 years ago, in the Balsas River valley southwest of Mexico City. The distribution of teosinte is restricted to tropical areas of Mexico and Central America, whereas Native Americans spread maize far from of its center of origin north to Canada and south to Chile before the arrival of Columbus. The genetics of maize domestication are well documented; a handful of genes with large effects on growth habit and reproductive morphology have been identified. Sequence differences at these genes (or in their regulatory regions) explain much of the change from highly branched teosinte plants with numerous female spikes each containing a single row of easily dispersed hard-coated seeds to maize plants with a single main stem bearing a few female ears, each containing many rows of non-dispersing ‘naked’ and ready to eat seeds. Remaining unexplained is how tropical maize, after its domestication, became adapted to the long daylengths and short growing seasons of higher latitudes. A recent paper by Guo et al demonstrates that two sequence changes in the regulatory region of the key flowering time gene ZCN8 were selected at different points in the history of maize, leading to earlier flowering plants adapted to temperate growing regions encountered as ancient humans moved maize northward from its origin, leading eventually to the highly productive Corn Belt varieties of the Midwestern USA.