(A–D) RNA in situ hybridization analysis of CsYAB5 in the cucumber shoot apex and flower buds. Longitudinal (panel A) and transverse sections (panel B) of cucumber shoot apex. p1–p6: leaf primordia 1–6. (C) Longitudinal image of a flower bud. (D) Transverse section of leaf primordia in the shoot apex, hybridized with the CsYAB5 sense probe. (E) Plant morphology of WT and CsYAB5-RNAi line R1, R2, and R3. (F) Leaf morphology of WT and CsYAB5-RNAi lines. White squares show the gap between the bilateral leaf margins. (G) qRT-PCR analysis indicates reduced expression of CsYAB5 in the CsYAB5-RNAi lines. (H–I) Fruit at anthesis in WT and CsYAB5-RNAi lines (panel H); quantification of ovary length at anthesis (panel I). (J–K) Reduced mature fruit length (panel J) and decreased seed viability (panel K) in the CsYAB5-RNAi line. (L) Morphology of mature seeds of WT and CsYAB5-RNAi line. (M–P) Transverse sections of leaf mid-veins of WT (panel M) and CsYAB5-RNAi (panels N–P) plants. (M’–P’) Amplified vascular bundles in red boxes of panels M–P. Blue stars in panels N’–P’ indicate extra vascular bundles in CsYAB5-RNAi lines. Scale bars represent 100 μm in panels A–D; 2 cm in panels E–F, H, and J–K; 1 mm in panel L; 500 μm in panels M–P; and 200 μm in panels M’–P’. Values are means ± SE (n = 3) in panels G and I. Double asterisks indicate significant difference at P < 0.01 by t test. The data underlying this figure are included in S3 Data. C, carpel; Cs, Cucumis sativus; ExP, external phloem; InP, internal phloem; P, petal; Ph, phloem; qRT-PCR, quantitative real-time PCR; RNAi, RNA interference; S, sepal; St, stamen; v, vascular tissue; WT, wild type; Xy, xylem; YAB5, YABBY5.