Volume 2, Issue 5, Pages 990-999 (September 2009) Pectin May Hinder the Unfolding of Xyloglucan Chains during Cell Deformation: Implications of the Mechanical Performance of Arabidopsis Hypocotyls with Pectin Alterations  Abasolo Willie , Eder Michaela , Yamauchi Kazuchika , Obel Nicolai , Reinecke Antje , Neumetzler Lutz , Dunlop John W.C. , Mouille Gregory , Pauly Markus , Höfte Herman , Burgert Ingo   Molecular Plant  Volume 2, Issue 5, Pages 990-999 (September 2009) DOI: 10.1093/mp/ssp065 Copyright © 2009 The Authors. All rights reserved. Terms and Conditions

Figure 1 Exemplary Stress-Strain Curves of a Standard Tensile Test and a Cyclic Loading Test on the Hypocotyls. (A) Wild-type hypocotyl in a standard tensile test illustrating how the tensile stiffness and the ultimate stress level (∼strength) of the hypocotyls were determined. (B) Mur1 hypocotyl in a cyclic loading test illustrating how the stiffness values of the different loading cycles and the “plastic deformation” in the 1st loading cycle (εplastic) were determined. Molecular Plant 2009 2, 990-999DOI: (10.1093/mp/ssp065) Copyright © 2009 The Authors. All rights reserved. Terms and Conditions

Figure 2 Ultimate Stress versus Stiffness Plots Displaying the Tensile Properties of the Hypocotyls Col-0: filled triangle, mur1: filled square, mur2: filled circle, qua2: filled diamond. (A) 4 day-old hypocotyls of Col-0, n = 91; mur1, n = 103; mur2, n = 84. (B) 6 day-old hypocotyls of Col-0, n = 38; qua2, n = 44; Error bars show standard deviations. In terms of ultimate stress levels t-tests revealed no significant differences between Col-0 and the pectin altered mutants (mur1 and qua2), but a significant differences between Col-0 and mur2 at a α = 0.01 level; in terms of stiffness mur1 and qua2 were significantly different from Col-0 at a α = 0.001 level and mur2 was significantly different from Col-0 at a α = 0.05 level, respectively. Molecular Plant 2009 2, 990-999DOI: (10.1093/mp/ssp065) Copyright © 2009 The Authors. All rights reserved. Terms and Conditions

Figure 3 Mechanical Response of the Hypocotyls to Cyclic Loading. (A-C) Exemplary cyclic loading curves of the three different types of the 4 day-old hypocotyls. (D,E) Exemplary cyclic loading curves of 6 day-old Col-0 (only the relevant segment of the full stress-strain curve is shown) and qua2 hypocotyls. (F-H) Average stiffness change in the first, second and third cycle of the three different types of the 4 day-old hypocotyls. Error bars show standard deviations; Col-0, n = 30; mur1, n = 36; mur2, n = 31. (I,J) Average stiffness change in the first, second and third cycle of 6 day-old Col-0 and qua2 hypocotyls. Error bars show standard deviations; Col-0, n = 21; qua2, n = 19. Molecular Plant 2009 2, 990-999DOI: (10.1093/mp/ssp065) Copyright © 2009 The Authors. All rights reserved. Terms and Conditions

Figure 4 Relative Stiffness and “Plastic Deformation” of the Hypocotyls in Cyclic Loading Tests. (A) Comparison of the relative stiffness in the first three loading cycles of the 4 day-old hypocotyls (Col-0, mur1, mur2) and the 6 day-old hypocotyls (qua2). (B) Percent strain of plastic deformation (εplastic) during the first cycle of the 4 day-old hypocotyls (Col-0, mur1, mur2) and the 6 day-old hypocotyls (qua2). Molecular Plant 2009 2, 990-999DOI: (10.1093/mp/ssp065) Copyright © 2009 The Authors. All rights reserved. Terms and Conditions

Figure 5 Turgor Pressures of the Hypocotyls. Turgor pressure of the 4 day-old hypocotyls (Col-0, mur1, mur2) and the 6 day-old hypocotyls (qua2) were calculated from water potential and osmotic pressure measurements. Error bars show standard deviations based on calculations of error propagation (Col-0, n = 37; mur1, n = 12, mur2, n = 36, qua2, n = 4). Molecular Plant 2009 2, 990-999DOI: (10.1093/mp/ssp065) Copyright © 2009 The Authors. All rights reserved. Terms and Conditions

Figure 6 Simple Structural Model of the Influence of the Geometrical Interactions of Folded Xyloglucan Chains with Pectin. Cell walls of hypocotyls with pectin alteration are illustrated with a wider mesh (CF, cellulose fibril; XG, xyloglucan chain; PE, pectin). (A) Initial state before straining with a given space between the fibrils D0. (B) Cell walls with pectin alterations (wider mesh) show larger plastic deformation after the first loading cycle than cell walls without pectin alteration (D0 < D1 < D2). Molecular Plant 2009 2, 990-999DOI: (10.1093/mp/ssp065) Copyright © 2009 The Authors. All rights reserved. Terms and Conditions