title: Evidence That the Origin of Naked Kernels During Maize Domestication Was Caused by a Single Amino Acid Substitution in tga1.
abstract: teosinte glume architecture1 (tga1), a member of the SBP-box gene family of transcriptional regulators, has been identified as the gene conferring naked kernels in maize vs. encased kernels in its wild progenitor, teosinte. However, the identity of the causative polymorphism within tga1 that produces these different phenotypes has remained unknown. Using nucleotide diversity data, we show that there is a single fixed nucleotide difference between maize and teosinte in tga1, and this difference confers a Lys (teosinte allele) to Asn (maize allele) substitution. This substitution transforms TGA1 into a transcriptional repressor. While both alleles of TGA1 can bind a GTAC motif, maize-TGA1 forms more stable dimers than teosinte-TGA1. Since it is the only fixed difference between maize and teosinte, this alteration in protein function likely underlies the differences in maize and teosinte glume architecture. We previously reported a difference in TGA1 protein abundance between maize and teosinte based on relative signal intensity of a Western blot. Here, we show that this signal difference is not due to tga1 but to a second gene, neighbor of tga1 (not1). Not1 encodes a protein that has 92% amino acid similarity to TGA1 and that is recognized by the TGA1 antibody. Genetic mapping and phenotypic data show that tga1, without a contribution from not1, controls the difference in covered vs. naked kernels. No trait differences could be associated with the maize vs. teosinte alleles of not1. Our results document how morphological evolution can be driven by a simple nucleotide change that alters protein function.
authors.affiliation: Laboratory of Genetics, University of Wisconsin, Madison, Wisconsin 53076.
authors.forename: Huai
authors.initials: H
authors.lastname: Wang
authors.affiliation: Laboratory of Genetics, University of Wisconsin, Madison, Wisconsin 53076.
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Studer
authors.affiliation: Laboratory of Genetics, University of Wisconsin, Madison, Wisconsin 53076.
authors.forename: Qiong
authors.initials: Q
authors.lastname: Zhao
authors.affiliation: DuPont Pioneer, Johnston, Iowa 50131.
authors.forename: Robert
authors.initials: R
authors.lastname: Meeley
authors.affiliation: Laboratory of Genetics, University of Wisconsin, Madison, Wisconsin 53076 jdoebley@wisc.edu.
authors.forename: John F
authors.initials: JF
authors.lastname: Doebley
mesh_terms: D019943:Amino Acid Substitution; D050976:Basic-Leucine Zipper Transcription Factors / Q000235:genetics*; D019143:Evolution, Molecular; D005638:Fruit / Q000033:anatomy & histology* / Q000378:metabolism; D005786:Gene Expression Regulation; D017343:Genes, Plant; D003313:Zea mays / Q000033:anatomy & histology / Q000235:genetics* / Q000378:metabolism
chemical_list: D050976:Basic-Leucine Zipper Transcription Factors
keywords: domestication; glume architecture; maize; teosinte; tga1