Fig. 3

IAA-driven DR5::GUS expression in IBA-cultured TCLs, and ASA1 expression under IAA, IBA, and MeJA + IBA. a–d Expression in TCLs treated with IBA (10 μM) for 8 (a-b) and 15 days (c-d). a-b Beginning of the signal in early meristemoids (a) and in ARPs (b). c-d DR5-signal in the quiescent centre and some initial and cap cells in the apex of elongating (c) and mature (d) ARs. e–t ASA1::GUS expression. e–g Expression in TCLs observed under the stereomicroscope at day 15 under IAA (10 μM) (e), IBA (10 μM) (f), or MeJA (0.01 μM) + IBA (10 μM) (g), showing differences in signal intensity and localization among the treatments at explant level, but not in the AR apex (Insets). h–l Histological analysis of the expression at 8 (h-i) and 15 (j-l) day in IAA-treated TCLs. h–i Expression in the endodermis derivatives (h) and in de novo formed xylary cells (arrow), and in the apex of the developing ARPs (i). j–k Widespread expression in the ARPs entrapped in the callus (j), and in the apices of the frequently fused ARs (k). l Faint expression in the meristematic cells of the xylogenic nodules. m–p Histological analysis of the expression at 8 (m-n) and 15 (o-p) days in IBA-treated TCLs. m–n High expression in the endodermis derivatives (m), and in the apical part of the forming ARPs (n). o–p Signal in the initial cells of the niche and in the protodermis of the apex of the elongating ARPs (o) and ARs (p), with faint expression in the columella in both cases. q–t Histological analysis of the expression at 8 (q-r) and 15 (s-t) days in MeJA + IBA-treated TCLs. q–r Strong signal in the endodermis derivatives (q), and in the apical part of the forming ARPs (r). s–t High signal in the initial cells of the niche and protodermis of the apex of the elongating ARPs (s), and ARs (t), with a lower expression in the columella in both cases. Bars = 20 μm (r, s), 40 μm (a-c, h, i, k-p, q, t), 50 μm (d, j, o), 500 μm (e-g and Insets)