Figure 8.

Production of IGs in single and multiple bhlh mutants in response to MeJA treatment. Model for the IG production in bhlh04/05/06 and myb34/51/122 mutants. A, The IG content of single and multiple bhlh mutants after MeJA treatment is shown. For GSL analysis, the mutant and wild-type (Col-0) plants were grown on MS plates for 2 weeks followed by transfer to plates supplemented with 50 µm of MeJA. The sum of the three major IGs (I3M, 4MO-I3M, and 1MO-I3M) are shown. Results are means ± se from four two independent experiments with four biological replicates each (n = 8). Values marked with asterisks are significantly different from Col-0 (Student’s t test; P < 0.01). B, Comparison of IG content in bhlh04/05/06 and myb34/51/122 in the presence or absence of MeJA. Mutant and wild-type (Col-0) plants were grown on MS plates free of additives or MS supplemented with 50 µm of MeJA. The sum of the three major IGs (I3M, 4MO-I3M, and 1MO-I3M) is presented. Results are means ± se from three independent experiments with four biological replicates each (n = 12). Values marked with asterisks are significantly different from Col-0 (Student’s t test; P < 0.05). C and D, A model for the biosynthesis of GSL by MYB and bHLH in Arabidopsis in triple bhlh04/05/06 and myb34/51/122 mutants is shown. Biosynthesis of GSL is blocked in the absence of both bHLH (C) and MYB (D) proteins; thus, both types of TFs are necessary to produce GSLs in planta. DW, Dry weight.