Figure 4.

MtYUC2 Expression Is Repressed by the MtCEP1/MtCRA2 Pathway and Correlates with a Reduced Auxin Response in Roots under Low-N Conditions.

(A) and (B) RT-qPCR analysis of the expression of MtYUC2 in R108, cra2-8, and cra2T-4 grown without N and treated with MtCEP1 peptides.

(A) Germinated seedlings were grown in solidified Fåhraeus medium (10 mM KNO₃) for 10 d and then transferred to Fåhraeus medium without N for 2, 8, 12, and 24 h.

(B) Germinated seedlings were grown in Fåhraeus medium (10 mM KNO₃) for 10 d and then transferred to the same medium containing 1 μM MtCEP1 peptides for 2, 8, 12, and 24 h.

The data were derived from three independent pools of roots. The data are means ± sd. All samples are normalized with R108 at 0 h, and a paired two-tailed Student’s t test was used (*, P < 0.05 and **, P < 0.01; Supplemental Data Set 3). ns, nonsignificant.

(C) Representative images of DR5:GUS staining of root tips (top) and emerging lateral roots (bottom) from two independent lines stably transformed with DR5:GUS in R108 or cra2-8. Germinated seedlings were grown in Fåhraeus medium containing 0.25 or 10 mM KNO₃ for 10 d. Images were acquired with an Olympus microscope equipped with an interference device. Bars = 100 μm.

(D) Free IAA content in the roots of cra2T-4 and R108 grown with 0 or 10 mM KNO₃ for 7 d. The data are means ± sd of three independent pools of roots, and significant differences were determined with an ANOVA with a posthoc Tukey’s test, as indicated by letters (P < 0.05; Supplemental Data Set 3).