|Buckler, Edward - Ed|
Submitted to: Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/12/2003
Publication Date: 11/14/2003
Citation: JAENICKE, V., BUCKLER IV, E.S., SMITH, B.D., GILBERT, T.P., COOPER, A., DOEBLEY, J., PAABO, S. EARLY ALLELIC SELECTION IN MAIZE AS REVEALED BY ANCIENT DNA. SCIENCE. 2003. v. 302. p. 1206-1208. Interpretive Summary: Maize was domesticated from teosinte, a wild grass, by farmers in Mexico between 6,000 and 10,000 years ago. As early farmers domesticated this crop from its wild relative, they selected for favorable traits, such as traits which increased yield or ease of harvest. Until recently, our knowledge of this early character selection in maize was limited to morphological features that were externally visible in corn cobs. The ability to determine gene sequences from plant DNA recovered from archaeological excavations, however, has made it possible to follow the genetic consequences of domestication over time for biochemical traits as well. In this study, we analyzed three genes involved in the control of plant architecture, protein synthesis and starch production from ancient corn cobs unearthed in caves in Mexico and the southwestern USA. Through this analysis, we can begin to pinpoint when particular genes were targeted for selection by early domesticators of maize.
Technical Abstract: Based on archaeological evidence, scientists estimate that maize was domesticated from teosinte roughly 6,250 years ago. The early history of character selection in this important crop, however, is limited in the archaeological record to morphological features discernable in cobs. In an effort to understand when biochemical traits (not observable in cob morphology) were selected by early farmers, we analyzed three genes, tb1, pbf and su1, involved in the control of plant architecture, storage-protein synthesis, and starch production, respectively. These genes are associated with phenotypic differences between maize and teosinte, and have been cloned and well characterized as to their function. After DNA extraction, amplification, and sequence reconstruction from ancient cobs found in Mexico and the southwestern USA, results revealed that alleles known to occur in modern maize at the genes tb1, pbf and su1 were already present in maize 4,400 years ago. Thus, selection by farmers had a profound genomic effect on maize diversity relatively early in the history of this important crop.