Expression of KAPP in wild-type and clv1-4 tissue. Labeled KAPP and CLV1-specific RNA probes were used for hybridization to sections of inflorescence meristem and floral tissue. (A–C) Serial sections of wild type tissue showing KAPP RNA is detected throughout the apical and young floral meristems and down the provascular tissue. (D) Section of a wild-type stage 3 flower where KAPP expression is reduced in sepal primordia. (E) CLV1 mRNA expression in the center of the apical and young floral meristems only. CLV1 is not expressed in stage 1 flowers. (F) Transverse section of the stem, below the SAM, showing the punctate ring of KAPP expression in the provascular tissue. (G) KAPP weak expression in the stamen and carpel primordia of a stage 7 flower; (H) KAPP expression in the pollen sacs and carpels of a stage 9 flower; (I) KAPP expression in the developing ovules. (J) KAPP is expressed throughout the enlarged SAM of a clv1-4 mutant. (K) KAPP is expressed in the central meristematic regions in mature clv1-4 flowers. (L) A KAPP sense probe hybridized to a wild-type inflorescence section. All photos are combined bright-field and dark-field exposures, with signal indicated by yellow grains. PV, provascular; SP, sepal primordia; St, stamen, Ca, carpel; PS, pollen sac; Pl, placenta; Ov, ovule; Si, silique wall; CM, central meristematic regions. Numbers indicate stages of floral development (all stages according to ref. 19). Bars = 40 μm.