Figure 4.

Genes involved in the development of xylem secondary cell walls are differentially regulated in the swt16swt17 double mutant. A–I, mRNAs were extracted from total inflorescence stems collected from 7-week-old wild-type, swt16, swt17, and swt16swt17 plants. The mRNA contents are expressed relative to those of the reference gene UBQ5. A, Heatmap of expression of candidate genes involved in xylem development and secondary cell wall biosynthesis in the inflorescence stem of the wild-type, and swt16, swt17, and swt16swt17 mutants. The values used to build the heatmap are the mean accumulation of transcripts (n=4) normalized by the median value of each gene and expressed as log₂ values. For each gene, the result of one-way ANOVA is displayed beside the heatmap. Those with P-values below the significance threshold (P<0.05) are in red. B–I, Boxplots showing the relative expression of SND1 (B), MYB46 (C), VNI2 (D), MYB4 (E), MYB83 (F), MYB54 (G), SND3 (H), and MYB103 (I). The box-and-whisker plots represent values from four biological replicates. The lines represent median values, the tops and bottoms of the boxes represent the first and third quartiles, respectively, and the ends of the whiskers represent maximum and minimum data points. Black dots are outliers. Stars denote significant differences between the mutant line compared to the wild-type according to a one-way ANOVA followed by a Dunnett post hoc test (*P<0.05; **P<0.01; ***P<0.001). The P-values for the comparison between the wild-type and swt16swt17 plants are indicated on each graph. The experiment was repeated twice and gave similar results.