(a) The genomic DNA sequence representing OsMads13 was annotated by cDNA/gDNA alignment. These data were used to design trait gene regulatory components, depicted by the solid black lines. The promoter is on the right and terminator is on the left. The size and orientation of each line indicates gDNA incorporated into each component. Open boxes represent non-transcribed sequence, grey is transcript, large grey boxes are exons, narrow grey boxes are introns. (b) OsMads13 expression cassette activity in T1 maize was assessed by histochemical localization of β-glucuronidase (GUS) protein. The left panels are central, longitudinal- and cross-sections of the ear. The right panel is a stem section taken at the ear node with the ear removed. Samples were harvested 5 days before pollination, and were incubated in the histochemical reagent for various times at 37°C then cleared with ethanol and photographed. The OsMads13 expression cassette is not active, i.e. a histochemical signal is not detected, in other plant tissues including silk, leaf, root and tassel52. The black bar in each image is 5 mm.