The bps1 SAM fails to express WUS. A to C, GUS staining in the SAM of 2, 3, and 4 dpi seedlings. In each, the top row shows the pattern in the wild type (Col-0 or Ler), and the bottom row shows the pattern in bps1 mutants. A, pSTM::GUS; B, pCLV3::GUS; C, pWUS::GUS. Bars = 50 µm.