Expression pattern and quantification of COM2 in two-rowed barley. (A–C) mRNA in situ hybridization of COM2 in two-rowed wild-type barley cv. Bonus. (A) Transverse section at triple-mound stage shows COM2 expression at sites of future glume primordia (GP) (red arrowhead). (B) Detail of immature spike with lateral spikelets (LSs) at GP stage reveal accumulation of COM2 transcripts between LS and outer glume. (C) Immature spike with LS in the GP stage showing semicircular COM2 expression between GP and LS primordia along the spike. Expression is clearer in the developmentally advanced basal part of the spike. Asterisks indicate central spikelet (CS) meristem (red), LS meristem (black), and GP (yellow), blue triangles point to the regions of gene expression. (D) COM2 expression in mutants BW-NIL(com2.g) and brc1.5 and wild type cv. Optic. LP and AP stand for lemma primordium and awn primordium stages, respectively. Mean ± SE of three biological replicates. Relative expression values are given at the bottom of the graph. The y-axis value shows the expression relative to HvActin, while genotype differences were tested at a significance level of P > 0.05.