Natural variation in teosinte at the domestication locusteosinte branched1(tb1)
Abstract
Premise of the study
Theteosinte branched1(tb1)gene is a major QTL controlling branching differences between maize and its wild progenitor, teosinte. The insertion of a transposable element (Hopscotch) upstream oftb1is known to enhance the gene’s expression, causing reduced tillering in maize. Observations of the maizetb1allele in teosinte and estimates of an insertion age of theHopscotchthat predates domestication led us to investigate its prevalence and potential role in teosinte.
Methods
Prevalence of theHopscotchelement was assessed across an Americas-wide sample of 837 maize and teosinte individuals using a co-dominant PCR assay. Population genetic summaries were calculated for a subset of individuals from four teosinte populations in central Mexico. Phenotypic data were also collected using seed from a single teosinte population whereHopscotchwas found segregating at high frequency.
Key results
Genotyping results indicate theHopscotchelement is found in a number of teosinte populations and linkage disequilibrium neartb1does not support recent introgression from maize. Population genetic signatures are consistent with selection on this locus revealing a potential ecological role forHopscotchin teosinte, but a greenhouse experiment does not detect a strong association betweentb1and tillering in teosinte.
Conclusions
Our findings suggest the role ofHopscotchdiffers between maize and teosinte. Future work should assesstb1expression levels in teosinte with and without theHopscotchand more comprehensively phenotype teosinte to assess the ecological significance of theHopscotchinsertion and, more broadly, thetb1locus in teosinte.
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