Fig. 3. FIL and YAB3 are necessary for proper SHP2 and FUL expression. GUS expression driven by the SHP2 promoter (A-E) or the ful-1 enhancer trap line (F-I). All plants stained for FUL GUS activity are heterozygous for ful-1. (A) In wild-type fruit, the SHP2::GUS reporter is active in the valve margins throughout the fruit at stage 14. (C) In cross section, reporter activity is visible in the ovules as well as the valve margins. (B,D,E) In fil yab3 fruit, SHP2 reporter activity is lost in the apical region of the fruit (B –,D) while ectopic reporter activity is present in the valves of the basal portion (B ++,E). (F,G) FUL GUS staining of a stage 12 wild-type gynoecium showing expression in the two valves as well as in the vasculature of the style (F) and replum (G). (H,I) In the fil yab3 gynoecium, reporter activity is absent from the valves but remains in the vasculature. Note the presence of a supernumerary carpel in the fil yab3 gynoecium (I). (J-N) Lignin staining of valve cells in mature fruit (stage 17). (J) 35S::FUL valves develop a lignified enb layer similar to wild type. (K) 35S::FUL is able to suppress most of the ectopic lignification that occurs at the base of fil yab3 mutants and is able to rescue enb layer lignification in the apical region (L). Note some ectopic lignification is still present in the basal region. (M) In ful mutants, valve mesophyll cells become ectopically lignified as a result of the expanded expression of valve margin identity genes. (N) In the apical region of ful fil yab3 fruits, however, all cells of the valves are unlignified including the enb layer, suggesting that the valve margin identity genes are not active. v, valve; vm, valve margin; r, replum; ov, ovule; st, style; vb, vascular bundle; gy, gynophore; EL, ectopic lignification. Scale bar: 0.5 mm (A), 1 mm (B), 100 µm (C,D,E), 200 µm (F,H), 50 µm (G,I-N).