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John Doebley studies the genetics of changes in plant form, especially the domestication of maize from teosinte. His own research profile describes quantitative genetics as a principal approach.^[ref]

In 1997, Doebley and colleagues identified teosinte branched1 as a regulator associated with the stronger apical dominance of maize. Higher expression in maize connected altered gene regulation to reduced lateral branching. This work made a major crop difference experimentally approachable as a change in a developmental programme rather than an inexplicable difference between two plant forms.^[ref]

A PNAS biographical profile includes a labelled photograph taken in 2003.

Maize is the domesticated grass Zea mays, grown for its grain. A maize kernel is a caryopsis: a fruit in which the enclosing wall is closely attached to the seed. The male flowers form the tassel, while female flowers occur in ears; wind carries pollen between them. Having both kinds of flowers on one plant is different from having separate male and female plants.

Its domestication from teosinte provides a concrete example of how changes in developmental regulation alter a crop. Research on apical dominance identified the teosinte branched1 gene as a major contributor to the suppression of side branches in maize. Comparing gene activity and mutant plants connected a conspicuous architectural difference to regulation of axillary growth.^[ref]

Teosinte is the common name for wild relatives of maize in the genus Zea. These grasses are useful for studying domestication because they preserve combinations of branching and reproductive traits that differ strikingly from cultivated maize. The name covers multiple wild forms rather than one uniform species.

Compared with the strongly dominant main shoot of typical cultivated maize, its wild progenitor has much more lateral branching. Experiments on teosinte branched1 connected part of this difference to altered gene expression and suppression of branch growth.^[ref] A familiar food crop can thus illuminate evolution: conspicuous differences in plant architecture can arise partly through changes in the regulation of an existing developmental system.

Teosinte branched1, conventionally written tb1 for the gene, encodes a transcription factor that suppresses outgrowth of lateral buds in maize. It is a major component of the difference in apical dominance between cultivated maize and its wild teosinte relatives.

John Doebley and colleagues connected tb1 expression and mutant morphology to suppression of axillary growth. Cultivated maize showed increased tb1 expression in the relevant comparison, linking altered regulation of a developmental gene to a conspicuous domestication trait.^[ref]

This illustrates why regulatory change matters: a large difference in branching need not require inventing an entirely new protein. Changing where or how strongly an existing regulator acts can reshape the plant.

Zea is a taxonomic genus of grasses that includes maize and its wild relatives, commonly called teosinte. Its native distribution is in Mexico and Central America; widespread cultivated and introduced populations should be distinguished from that native range.^[ref]

The plants exhibit monoecy: male and female flowers occur on the same plant, in separate inflorescences. The male inflorescence is terminal, while the female inflorescences are borne in leaf axils. In maize, the conspicuous male structure is the tassel, and the female structure develops into the ear. Thus an ear and a tassel are different reproductive structures of one plant.^[ref]

Comparing maize with teosinte makes Zea a powerful system for studying domestication. Differences in branching can arise through changes in gene regulation: work on the teosinte branched1 gene connects the compact architecture of cultivated maize with altered control of shoot development.^[ref]