Fig. 2. RNA in situ analysis of HEC expression during gynoecium development in Arabidopsis. (A-C) Transverse sections through stage 8 gynoecia. HEC1, HEC2 and HEC3 are expressed in the developing septum (arrowheads). The HEC1 signal seen in the anthers at this stage (double arrowhead) was not seen for HEC2 or HEC3 and was not duplicated by the HEC1 GUS reporter (see Fig. S1E in the supplementary material). (D-F) Transverse sections through early stage 12 gynoecia. HEC1, HEC2 and HEC3 expression becomes localized to the developing transmitting tract (arrowheads). HEC1 and HEC2 are expressed in ovules (small double arrowheads) and HEC3 shows expression in the ovule funiculus (arrow). (G,H) Longitudinal sections through stage 8 and stage 11 flowers. HEC1 (G) and HEC3 (H) expression is evident in the developing septum and transmitting tract (arrowheads) and stigma (arrows). (I,J) Longitudinal and transverse sections through late stage 12 gynoecia. HEC3 continues to be strongly expressed in the transmitting tract (large arrowheads) and ovule funiculus (small arrowheads), but not in the stigma (arrow). HEC1 and HEC2 expression can no longer be detected at this time (data not shown). Scale bars: 50 µm.