Figure 3. Threefold screw xylan is abundant in irx3 but not in wild type as shown by analysis of mobile cell wall components.

An overlay is shown of ¹³C refocussed DP-INADEQUATE ¹³C NMR spectra of wild type and irx3 never-dried Arabidopsis stems using a 1.9 s recycle time, which emphasize relatively mobile species. The carbohydrate region of the spectrum is expanded to focus on the Xn4→Xn5 connection. This shows that threefold xylan is abundant in irx3, and the twofold xylan is relatively immobile and so is not detected in wild type or irx3 mutant cell walls. Xylose of threefold xylan is highlighted in green. Dotted red squares indicate the absence of the twofold screw Xn4→Xn5 pair. The change in some arabinose and pectin structures in the plants may be due to altered growth of the dwarfed irx3 plant. The spectrum of the full carbohydrate region is shown in Supplementary Figure 5, and was recorded with a spin-echo duration of 2.2 ms at a ¹³C Larmor frequency of 213.8 MHz and a MAS frequency of 12 kHz.