Combining multivariate analysis and monosaccharide composition modeling to identify plant cell wall variations by Fourier Transform Near Infrared spectroscopy

Plant cell walls are a complex mixture of polysaccharides, proteins and the phenolic polymer lignin that have been recently targeted as possible sources of fermentable sugars for the production of biofuels and other bio-materials [1]. The development of a lignocellulose biomass-based biofuels industry is partly dependent on genetic engineering and breeding of the next generation of crops containing, among other traits, easily extractable cell wall sugars. Thus, a better understanding of how plants synthesize, deposit and modify their cell walls is necessary for the selection of traits important for biofuel crop improvement [2].The identification of plants with altered cell wall composition or structure can prove useful in the discovery of novel genes involved in the biosynthesis and modification of the cell wall. Such plants can be isolated using genome-wide association mapping of diverse populations or can be isolated from forward genetic screens, where a subset sample population with the desired traits is selected from a large pool of mutagenized individuals. However, the identification of these select samples requires a well-constructed screening process that is both robust and, due to the large sample population, high-throughput. Several successful plant cell wall mutant screens have been described over the years that make use of different screening methodologies. These include: acid hydrolysis and monosaccharide composition using gas-liquid chromatography [3], microscopic observation of xylem stem sections [4,5], seedling growth on medium containing cell wall hydrolyzing enzymes [6] and Fourier-Transform Infrared (FT-IR) microspectroscopy [7,8]. Most of these approaches either required at least some kind of sample processing or were not amenable to high-throughput screening, especially when dealing with, in some cases, thousands of mutagenized plant samples. In addition, most of these screens have been performed on the model species Arabidopsis thaliana, a dico