Figure 10.

Expression of the Secondary Wall–Associated Laccase4 Gene Is Induced by MYB58 and MYB63.

The expression of LAC4 and LAC17 was studied using real-time quantitative RT-PCR. The quantitative differences of their expression between the control and the treated samples are statistically significant (P < 0.001). Error bars represent se of three biological replicates.

(A) LAC4 and LAC17 were expressed highly in interfascicular fibers and xylem cells. RNAs used for gene expression analysis were isolated from laser-microdissected cells. The expression levels of LAC4 and LAC17 in the pith cells are set to 1.

(B) LAC4 and LAC17 were expressed predominantly in inflorescence stems. Their expression levels in leaves are set to 1.

(C) Overexpression of MYB58 and MYB63 induced the expression of LAC4 but not LAC17. Arabidopsis leaf protoplasts were transfected with the CaMV 35S promoter–driven MYB58 (MYB58-OE) and MYB63 (MYB63-OE) expression constructs or an empty vector (control). The expression levels of LAC4 and LAC17 in the control are set to 1.

(D) and (E) Direct activation of the LAC4 gene by MYB58. Arabidopsis leaf protoplasts were transfected with the CaMV 35S promoter–driven MYB58-HER construct. Estradiol activation of MYB58 induced the expression of LAC4 (D), and this induction still occurred when new protein synthesis was completely inhibited by cycloheximide (E). The expression level of LAC4 in the mock-treated (control) or cycloheximide-treated (CHX) protoplasts is set to 1.