Analysis of gene mutation in plant cell wall by dielectric relaxation

Abstract

Arabidopsis Thaliana is a plant composed mainly of cellulose and lignin. Geneticists need techniques able to make differences at the molecular level between modified plants (DML6, CAD C/D) and non-modified ones. Thermo-stimulated current (TSC) analysis is a promising route to identify gene mutations. For the non-modified plant, at low temperatures, TSC thermograms highlight three dielectric relaxation modes. From −150 to −110 • C, γ Cellulose is attributed to CH 2 OH and-OH groups of cellulose. Between −110 and −80 • C, β Lignin is detected. From −80 to −40 • C, β Cellulose is characteristic of the molecular mobility of glycosidic linkages. For the CAD C/D modified plants, only γ Cellulose and β Lignin are observed; due to analogous enthalpy values, those modes have the same molecular origin as in the non-modified plant. So, the β Lignin mode is associated with the molecular mobility of the lignin-OH groups. The CAD C/D gene mutation changes the chemical structure of lignin, which promotes hydrogen bonds in the network and inhibits molecular mobility of glucosidic rings. It is also interesting to note that the DML6 gene mutation induces a higher cooperativity of this β Cellulose relaxation than in wild vegetal composites. In fact, this mutation promotes molecular mobility of glycosidic rings thanks to β 1-4 glycosidic linkages.

Dielectric and mechanical properties of various species of Madagascan woods

“…Jafarpour et al (2008) found two components for the dielectric manifestation of poplar glass transition: one associated with the response of cellulose and the second associated with lignin. Roig et al (2011bRoig et al ( , 2012) associated b Lignin with the molecular mobility of hydroxyl group of lignin; this assignment sounds consistent with the observed data.…”

“…This broad relaxation was also resolved into elementary thermograms. The molecular origin of this relaxation mode is the mobility of OH groups of lignin (Roig et al 2012(Roig et al , 2011b. Data extracted from the series of elementary thermograms permit to plot the variation of the activation enthalpy DH versus temperature (Fig.…”

Explaining the heat capacity of wood constituents by molecular vibrations

“…Secondary relaxations have been found in both cellulose and lignin in their native form [23]. For the latter, b-relaxation is found in the 153-223 K temperature range centred around 187 K [23], and can be attributed to OH-group mobility [24]. Thus, this motion may already be at least partly included as OH-vibrations in the heat capacity calculations, and might explain why no conformational contribution is needed to explain the experimental data of lignin.…”