Figure 1.

SHR Regulates Phloem Development in the Arabidopsis Root.

(A) A schematic diagram showing the Arabidopsis root anatomy and asymmetric cell divisions of two precursor cells for phloem sieve element formation, as indicated by the flipped T shape in white. Comparison of phloem development between wild-type and shr-2 roots.

(B) and (C) Transverse sections through the maturation zones of wild-type (B) and shr-2 (C) roots, stained with toluidine blue. Scale bar = 10 μm. Asterisks, pericycle position; arrows, xylem axis; red arrowheads, sieve elements. WT, wild type.

(D) and (E) Immunolocalization of the SE-ENOD in wild-type (D) and shr-2 (E) roots. Asterisks, pericycle position; arrows, xylem axis. WT, wild type.

(F) to (M) Expression of of two representative phloem markers. ProAPL:erGFP in the wild type ([F] and [J]) and shr-2 ([G] and [K]), and expression of ProSUC2:erGFP in wild type ([H] and [L]) and shr-2 ([I] and [M]). Arrows, xylem axis; red arrowheads, sieve elements; white arrowheads, beginning of the transition zone of the root. WT, wild type.