Fig. 5. ULT1 and ULT2 mRNA expression patterns in inflorescence and flower tissues. RNA localization by in situ hybridization with ULT1 (A,D,H) and ULT2 (B,F,I) antisense probes hybridized to wild-type Ler tissues. (A-C) Longitudinal sections through the inflorescence meristem (ifm) and adjacent floral meristems (fm). ULT1 mRNA is localized throughout the inflorescence meristem. No signal was detected in stage 1 floral meristems (white arrowheads). ULT1 transcripts reappeared in late stage 2 floral primordia (black arrowheads). As soon as the sepals initiate (stage 3 flower), ULT1 expression becomes restricted to the center of the floral meristem. (C) Control hybridization with an ULT2 sense probe. (D-G) Longitudinal sections through stage 7-8 flowers. ULT1 (D) and ULT2 (F) mRNA was detected in stamen (St) and carpel (Ca) primordia. In both cases the signal appears stronger on the adaxial side of the carpels (arrows). (E,G) Control hybridizations with ULT1 and ULT2 sense probes. (H-J) Transverse sections through mature flowers. ULT1 (H) and ULT2 (I) mRNA was detected in ovules (white arrowheads) and tapetum tissue in the anthers (black arrowheads). (J) Control hybridization with an ULT1 sense probe. Scale bars: 50 µm.