GSL accumulation is significantly reduced in rosette leaves of double bhlh04/05 and triple bhlh04/05/06 mutants. A, GSL levels in single and multiple bhlh mutants are shown. For GSL analysis, leaves of 6-week-old plants were harvested and the sum of the three major IGs (I3M, 4MO-I3M, and 1MO-I3M), the sum of the four main AGs (3MSOP, 4MSOB, 5MSOP, and 8MSOO), and the sum of IGs and AGs are shown as Sum GSL. 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 < 0.01). B, Expression of GSL biosynthetic genes in the triple bhlh mutant is shown. Relative expression values of biosynthesis genes for AG (CYP79F2 and CYP83A1), IG (CYP79B2, CYP79B3, CYP83B1, and SOT16) and both AG and IG (C-S lyase and PAPST1) are shown. Relative expression was measured in leaves of 6-week-old bhlh04/05/06 knock-out lines (Col-0 = 1). Data are means ± se from three independent experiments with three biological replicates each (n = 9). Values marked with asterisks are significantly different from control plants (Student’s t test; P < 0.05). DW, Dry weight.