Figure 2.

Mutations in AtXTH4 and AtXTH9 affect XET activity in stem and hypocotyl, stem height, and XG signals in secondary vascular tissues. A, Positions of T-DNA inserts in AtXTH4 and AtXTH9 genes, and expression of target genes in mutant single insert lines and in the double mutant analyzed in inflorescence stem base and in secondarily thickened hypocotyls by reverse transcription quantitative PCR (RT-qPCR). ND, Not detected; WT wild type. Error bars indicate se. B, XET activity in protein extracts from the basal part of inflorescence stems and in hypocotyls of 6-week-old xth4 and xth9 mutants, double mutant xth4x9, and line OE18 with strong heterologous expression of PtxtXTH34 determined by the incorporation of ³H-labeled XG oligosaccharide acceptor to insoluble residue and normalized to tissue fresh weight. C, Stem height in 6-week-old plants grown in long-day conditions. In B, P values for the post-ANOVA Student’s t test are shown, and in C, significant differences from the wild type are shown by percentage change (post-ANOVA Student’s t test, P ≤ 5%). Values are means ± se; n = 5 and 30, respectively. D, Immunolocalization of XG with CCRC-M1 antibody in vascular tissues of basal stem and hypocotyl of 6-week-old plants. Arrows point to cambium. IFF, Interfascicular fibers; PH, phloem; X, xylem. Bar = 50 µm.