Fig. 5. bif2 is required for branch meristem formation: expression analysis with kn1. (A) RNA in situ hybridization of kn1 in a normal male inflorescence. kn1 is strongly expressed in the inflorescence meristem (im) and is downregulated on the flanks of the inflorescence as bract primordia initiate (br). Branch meristem initials (bi) are visible as a small group of kn1-expressing cells separating successive bract primordia. kn1 is highly expressed in branch meristems (bm) as they grow out. (B) kn1 RNA in situ hybridization in a bif2 male inflorescence. In this example, the inflorescence apex is fasciated and has split into two growing points. As in normal inflorescences, kn1 is expressed in the inflorescence meristem and is downregulated as bract primordia (br) initiate. Unlike normal, kn1 is not expressed on the flanks of the inflorescence and there is no evidence of branch meristem formation or branch meristem initials. (C) Immunolocalization of KN1 protein in a bif2 male inflorescence. KN1 protein is found in the inflorescence meristem but not on the flanks of the meristem. Note that KN1 protein extends into the epidermal layer of the inflorescence meristem (Smith et al., 1992; Jackson et al., 1994). (D) kn1 RNA in situ hybridization in a normal female inflorescence. kn1 is expressed in the inflorescence (im), branch (bm) and spikelet meristems (sm) as well as in the stem and vasculature. (E) kn1 RNA in situ hybridization in a bif2 female inflorescence. kn1 RNA is not present on the flanks of the inflorescence owing to the absence of branch, spikelet and floral meristems. (F) kn1 RNA in situ hybridization in a fasciated bif2 female inflorescence. Down regulation of kn1 within the inflorescence meristem occurs when the inflorescence apex has split into separate growing points. Bi, branch meristem initials, bm, branch meristem; br, bract primordium; im, inflorescence meristem;,sm, spikelet meristem. Scale bars, (A-C) 100 µm; (D-F) 300 µm.