A multivariate statistical analysis approach to highlight molecular processes in plant cell walls through ATR FT-IR microspectroscopy: The role of the α-expansin PhEXPA1 in Petunia hybrida

Mid-infrared ATR FT-IR microspectroscopy is applied in conjunction with multivariate statistical analysis on petal samples of Petunia hybrida from wild-type and from two transgenic lines in which the PhEXPA1 expansin gene expression was down-regulated and up-regulated, respectively. New insights are given on the role of expansin in the rearrangement of the cell wall polymer network. Measurements are done without any previous sample treatment to preserve the native cell wall structure and natural biological variability. An original combination of data analysis techniques is proposed to highlight molecular processes in plant cells, based on an automated spectra selection procedure, Principal Component Analysis, Wilcoxon rank sum test and heat map data representation.