SHR Movement into the Phloem Pole Is Required for Asymmetric Cell Divisions for Sieve Element Development.
(A) to (L) Confocal cross sections of the root meristematic zone of ProCRE1:SHRΔNLELDV-nlsGFP shr-2
(A) and ProS32:SHRΔNLELDV-nlsGFP shr-2
(D) show the GFP signal indicating the expression pattern of the nonmobile SHR protein. Toluidine blue–stained transverse sections and immunolocalization of the SE-ENOD of ProCRE1:SHRΔNLELDV-nlsGFP shr-2 ([B] and [C]) and ProS32:SHRΔNLELDV-nlsGFP shr-2 ([E] and [F]) are shown. Confocal cross sections of the root meristematic zone and immunolocalization of the SE-ENOD of ProEPM>>iCalsM3 ProSHR:SHR-GFP shr-2 ([G] to [L]) are also shown.
(G) to (I) Without an estradiol treatment, SHR movement and SE development are normal.
(J) to (L) Images taken 2 d after a treatment with 10 µM of estradiol. The phloem pole, indicated by white arrowheads, does not show SHR-GFP. Scale bar = 10 µm; asterisks, pericycle position; arrows, xylem axis; arrowheads, SEs.