Double RNA FISH to show the spatial separation of different mRNAs. Gene-specific probes were labeled with digoxigenin or fluorescein isothiocyanate (FITC) and detected by TSA-Cy5 (magenta signals) or TSA-FITC (green signals), respectively. A, SAM overview showing the expression patterns of primordia-specific AHP6 mRNA with meristem-expressed STM mRNA. B, Expression patterns of AP3 and AHP6 in the same tissue section of the shoot apex. C and D, Spatial separation of AP3 and AHP6 mRNAs in stage 4 (C) and stage 5 (D) flowers. ca, Carpel; pe, petal; se, sepal; st, stamen. Bars = 25 μm.