Figure 2.

Overexpression of the antisense form of the miR165a gene causes an alteration in vascular patterning. The antisense form of the miR165a gene was overexpressed under the cauliflower mosaic virus 35S promoter in wild-type Arabidopsis. Transgenic plants were selected and their inflorescence stems were sectioned and stained with toluidine blue for visualization of the vascular anatomy. (A) Section of a wild-type stem showing the regular arrangement of vascular bundles and interfascicular fibers in the stele. (B) High magnification of a wild-type vascular bundle showing the collateral vascular pattern with the xylem and phloem in parallel. (C) Section of an antisense-miR165a stem showing the aberrant formation of a vascular bundle in the middle of the stele (arrow) in addition to the normal vasculature. (D) High magnification of the misplaced vascular bundle in the antisense-miR165a stem showing an amphivasal vascular pattern with xylem (arrows) surrounding phloem. (E) High magnification of a normally placed vascular bundle in the antisense-miR165a stem showing xylem cells (arrows) arranged in a circular pattern. co, cortex; if, interfascicular fiber; ph, phloem; pi, pith; xy, xylem. Bars in (A) and (C), 197 µm and bars in (B), (D) and (E), 82 µm.