Implications of an inverted duplication in the wheat KN1-type homeobox gene Wknox1 for the origin of Persian wheat

Abstract

Introgression between related species with different ploidy levels has played important roles in wheat subspecies differentiation. Persian wheat, a cultivated tetraploid wheat subspecies (Triticum turgidum subsp. carthlicum), is postulated to have evolved through interploidy hybridization between tetraploid and hexaploid wheats. Here, we report evidence for the origin of subsp. carthlicumbased on the discovery of a new allele for the 5th-to-6th exon region of the Wknox1b KNOTTED1-type homeobox gene in a common wheat subspecies (T. aestivum subsp. carthlicoides). In this Wknox1b region, subsp. carthlicoides contains an inverted duplication mutation in the 3’ flanking region of a 157-bp MITE insertion site. This structural mutation resulted in the suppression of Wknox1bexpression in subsp. carthlicoides, but no structural mutation was observed in the same region of subsp. carthlicum. In addition, the carthlicum allele for the Wknox1b 5th-to-6th exon region exhibited the same sequence as that in the wild emmer wheat subsp. dicoccoides. These observations support an alternative hypothesis that subsp. carthlicum evolved by interploidy hybridization between subsp. carthlicoides and tetraploid wheat.