Ideal crop plant architecture is mediated by a BTB/POZ ankyrin repeat gene directly targeted by TEOSINTE BRANCHED1.

Axillary branch suppression is a favorable trait bred into many domesticated crop plants including maize compared with its highly branched wild ancestor teosinte. Branch suppression in maize was achieved through selection of a gain of function allele of the transcription factor that acts as a repressor of axillary bud growth. Previous work indicated that other loci may function epistatically with and may be responsible for some of its phenotypic effects. Here, we show that mediates axillary branch suppression through direct activation of the () gene that encodes an ankyrin repeat domain protein containing a motif necessary for protein-protein interactions. The expression of TRU1 and TB1 overlap in axillary buds, and TB1 binds to two locations in the gene as shown by chromatin immunoprecipitation and gel shifts. In addition, nucleotide diversity surveys indicate that , like , was a target of selection. In modern maize, TRU1 is highly expressed in the leaf trace vasculature of axillary internodes, while in teosinte, this expression is highly reduced or absent. This increase in TRU1 expression levels in modern maize is supported by comparisons of relative protein levels with teosinte as well as by quantitative measurements of mRNA levels. Hence, a major innovation in creating ideal maize plant architecture originated from ectopic overexpression of in axillary branches, a critical step in mediating the effects of domestication by