Fig. 2: Activation of the Schengen-pathway triggers the deposition of a distinct “stress” lignin in the endodermis.
From: Two chemically distinct root lignin barriers control solute and water balance
a Raman spectra of lignin of the different regions of interest presented in Supplementary Fig. 1 and determined using a Multivariate Curve Resolution (MCR) analysis. The MCR analysis was performed on small Raman maps from independent plants containing CS lignin of WT (n = 8), cell-corner lignin of WT treated with CIF2 (+CIF2; n = 5) and for xylem lignin of WT (n = 2) and xylem lignin of WT treated with CIF2 (n = 2). b Close view of Raman spectra presented in (a) in the lignin aromatic region between 1550 and 1700 cm−1. c Large Raman maps in root cross-sections of WT and WT treated with CIF2 (+CIF2). The intensity of the different lignin spectra presented in (a) was mapped onto large Raman maps containing xylem and endodermal lignin. Scale bar = 5 µm. d Lignin staining with basic fuchsin at a distance of 3 mm from the root tip in WT, ahp6-1, ahp6-1 esb1-1, ahp6-1 esb1-1 sgn3-3, ahp6-1 myb36-2 and ahp6-1 treated with CIF2. The plants were grown for 6 days in presence of 10 nM 6-Benzylaminopurine (BA). Upper panel shows a maximum projection of the root (scale bar = 10 µm). Spiral structures in the centre only observed in the WT root are protoxylem. Lower panel shows surface view of endodermal cells. The experiment was repeated two times independently with similar results (scale bar = 5 µm). White arrows indicate ectopic lignification. e Relative abundance of the lignin monomers released by thioacidolysis (p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) units) in root tips of ahp6-1 (n = 9), ahp6-1 treated with CIF2 (+CIF2; n = 3), ahp6-1 esb1-1 (n = 6), ahp6-1 myb36-2 (n = 6) and ahp6-1 esb1-1 sgn3-3 (n = 6). Asterisks represent significant differences from the ahp6-1 control for each individual monomer using a two-sided Mann–Whitney U test (p value < 0.05).
