Amino acid conservation in the HvHOX1 homeodomain. AA conservation in the HvHOX1 homeodomain was assessed by a sequence comparison of 100 different homeodomains (homeodomain smart accession No. 00389) provided by NCBI's Conserved Domain Database (CDD) [61, 62]. Highly conserved AAs are highlighted in red, whereas less conserved AAs are highlighted in blue. Positions of the AAs in each protein are indicated with numbers flanking the corresponding peptide, and AAs are given in single letter code. Asterisks above the HvHOX1 sequence indicate induced and non-synonymous substituted AAs detected in 21 barley mutants. The corresponding mutant lines together with the respective AA substitutions are shown in the boxes above. Mutations obtained from the 'Barke' mutant population are depicted in bold letters. The remaining mutations originate from alleles of the cultivars 'Bonus,' 'Foma' and 'Kristina,' as previously described by . The homeodomains of the proteins Antennapedia (Antp) (Schistocerca americana, American grasshopper) and Engrailed (En) (Drosophila virilis) were used as references for the localisation of the functionally relevant AAs in HvHOX1, as previously described [29–32]. The main structural features are indicated by α, core AAs involved in the determination of the three-dimensional protein structure; and β, AAs implicated in DNA binding. A model of the secondary structure of the HD peptide is indicated below the alignment, beginning with the N-terminus.