Figure 1.

The role of MONOPTEROS (MP) in root apical meristem (RAM) maintenance and lateral root patterning in Arabidopsis.

(a,b) 9d after germination (DAG) mp nph4 MP-GR^er seedlings grown in the absence of dexamethasone (DEX). Disorganized lateral roots (arrowheads) and inactive primary root tip (arrow) are indicated.

(c–f) Confocal images of primary roots. (c) 4DAG mp nph4 MP-GR^er grown on 15μM DEX. RAM is normal and resembles 4DAG nph4 root (d). (e) 4DAG and (f) 6DAG mp nph4 MP-GR^er RAMs grown in the absence of DEX. Arrowheads indicate epidermal root hair cells.

(g) Lateral roots from mp nph4 MP-GR^er seedlings grown on 15μM DEX.

(h,i) Confocal images of nph4 lateral roots showing normal RAM.

(j–l) Time course (j) and confocal images (k,l) of lateral root primordia (LRPs) from mp nph4 MP-GR^er seedlings grown in the absence of DEX. Arrowheads denote root hairs.

(m–x) PIN1-GFP in LRPs (distal tip to the right). (m–p) Wild type. (q–x) mp nph4 MP-GR^er germinated and grown continuously with (q–t) or without (u–x) 15μM DEX. Transverse and lateral cell membranes are denoted by white and red arrowheads, respectively. Ratios of LRPs exhibiting the depicted PIN1-GFP distribution and intensity are shown. LRPs in (u–x) are also depicted as rainbow spectrum look-up-tables (LUTs) to show relative PIN1-GFP expression. LRP stages are according to Malamy & Benfey (1997).

Bars: (a) 1mm; (b) 0.5mm; (c–f,h,i,k,l) 50μm; (g,j) 0.2mm; (m–x) 20μm.