Figure 6.

ChCUC and ChAS1 define boundary domains of ChBP expression. (A–D) ChAS1 expression in the C. hirsuta SAM and leaves analyzed by RNA in situ hybridization. ChBP::VENUS; PIN1::PIN1-GFP expression (E–H) and ChCUC2g-VENUS; PIN1::PIN1-GFP (I–L) in the C. hirsuta SAM and young leaves. (Red) Venus fluorescence; (green) GFP fluorescence; (blue) chlorophyll autofluorescence. Shown are transverse (A,E,I) and longitudinal (B,F,J) sections through the SAM; leaf 5 at a length of 750 µm (C,G,K); and a close-up of developing lateral leaflets (D,H,L). (M) Cartoon summarizing the observed ChAS1, ChBP, and ChCUC2 expression patterns. In leaf primordia, ChBP is expressed in the adaxial side and at the margin of the rachis (F,G) as well as at the tip of developing leaflets (H). (H,L) This expression pattern is near complementary to that of ChAS1 and overlaps with that of ChCUC2 in the leaf rachis margin at leaflet boundaries (arrowheads). This results in the formation of boundary domains (outlined with dotted lines) that are highly sensitive to ChBP dose and required to promote leaf growth. Bars, 100 µm. (R) Leaf rachis; (LL) lateral leaflet. Asterisks mark the SAM.