Fig. 1. ACL5 is specifically expressed in the xylem vessel elements. (A-E) In situ hybridization of ACL5. Sections were taken from the junction between the silique and the pedicel (A,B) and the basal part of the inflorescence stem (C-E), and analyzed using antisense (A,C,E) or sense (B,D) probes for the ACL5 gene. (A,B) Longitudinal sections; (C-E) an area of the stem with the vascular bundles in the transverse plane. The sections hybridized with the sense probe showed sometimes dark coloration of the vascular tissues (B) but not the positive purple precipitate derived from the chromogenic substrate (A,C,E). (F-H) Histochemical β-glucuronidase (GUS) staining of transgenic Pro_ACL5:GUS seedlings. Transverse sections were taken from the inflorescence stem (one vascular bundle shown in F), the hypocotyl of a 4-day-old seedling (G) and the hypocotyl of a 1.5-month-old seedling (H). do, developing ovary; pc, procambium; ph, phloem; sx, secondary xylem; v, vessel element; vc, vascular cambium; xp, xylem parenchyma. Asterisks indicate the protoxylem poles (G). Scale bars: 20 µm in E-G; 50 µm in C,D,H; 100 µm in A,B.