Fig. 6. Expression of IDA::GUS, BAC::GUS and CHIT::GUS in wild type and bop1 bop2. Arabidopsis floral positions are indicated in the upper right of panels. (A) Wild-type (C24xCol-0) flowers at position 3 show very weak IDA::GUS activity in the base of floral organs that intensifies throughout position 4 and 5. (B) IDA::GUS expression in bop1 bop2 (Col-0xC24) is detected at position 4 and more strongly in position 5. (C,D) Dark-field microscopy of stained IDA::GUS flowers in wild type (C) and bop1 bop2 show staining throughout the proximal sepal. (E,F) BAC::GUS in wild type (Col-0) or bop1 bop2 at positions 1, 3-6 stained for GUS activity. (E) BAC::GUS plants show strong staining at the base of all floral organs, especially concentrated in the vasculature of position 1 and 3 flowers. Activity persists in position 4 and 5 flowers during abscission and is visible in single AZ cells (arrow). (F) BAC::GUS bop1 bop2 flowers at position 1 show weak staining at the bases of petals and stamens, and strengthens and enlarges by position 3. Very slight expression is detected on the adaxial side of sepals in position 4. (G,H) CHIT::GUS expression from flowers in wild type (Col-0) or bop1 bop2 at positions 3-7. (G) CHIT::GUS position 3 and 4 flowers demonstrate weak GUS staining, while positions 5 and 6 exhibit very strong AZ staining. (H) CHIT::GUS bop1 bop2 position 3 and 4 floral organs show weak GUS activity at their base. GUS activity is stronger in position 5. Staining is maintained in position 6 flowers extending further into the base of these floral organs. Arrowheads indicate expression. f, stamen filament; p, petal; s, sepal. Scale bars: 0.5 mm in A,B,E-H; 35 µm in C,D.