Fig. 1.

Arabidopsis thaliana MYB36 is expressed in the lateral root primordia (LRP) boundary cells at mid stages of lateral root development. (a) Images showing the length of primary root of 6 and 10 d post sowing (dps) Col-0, myb36-5, myb36-2 and myb36-6 mutants. (b) Localization of MYB36, using a rMYB36:GFP fusion protein, in the nuclei of root meristem endodermal cells. (c) Emerged lateral root density in Col-0, myb36-5, myb36-2 and myb36-6. Measurements were taken 10 dps on Murashige and Skoog (MS) agar plates. Lateral root (LR) density was calculated by dividing the number of lateral roots by the primary root length for each seedling (70–100 seedlings). The density is reported as the number of lateral roots per centimetre of primary root ± SD. Statistical significance: ***, P < 0.01. (d–g, j) Midplane and (h, i) front views of LRP at different developmental stages showing that rMYB36:GFP fusion protein localized specifically to the LRP boundary (LRPB) cells that delimit the primordia. Small white arrowheads point to the nuclei labelled with MYB36-GFP. (k) MYB36 expression determined with a transcriptional pMYB36:GUS fusion revealed that MYB36 is expressed inside the LRP, not in the endodermis, from stages V onwards, and during emergence of lateral roots. P, pericycle; En, endodermis; C, cortex; Ep, epidermis. (l, m) Midplane and front views, respectively, of LRPB cells of plants expressing pMYB36:GUS.