Dependence of Plant Cell Wall Composition and Structure on Cellulose Synthase-Like Knock Out Mutant

Abstract

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. The development of a biomass-based biofuels industry is partly dependent on genetic engineering and breeding next generation 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. 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.The CELLULOSE SYNTHASE-LIKE 6 (CSL6) gene has been recently shown to mediate the biosynthesis of mixed-linkage glucan (MLG), a cell wall polysaccharide that is thought to be necessary for cell wall expansion in the primary cell wall of young seedlings. A detailed analysis of a loss-of-function MLG rice mutant has been recently conducted revealing surprising results. Though the mutant showed a 99% reduction of MLG content, the rice clsf6 knock out mutant showed only a slight decrease in growth compared to wildtype. The cell wall properties of both mutant and wild type were determined via biochemical and various spectroscopic (Fourier Transform Mid-Infrared spectroscopy) analyses. We found that not only was the composition of the cell wall dramatically altered, but the overall structure of the cell wall was affected demonstrating the flexibility of plant polysaccharide organization to compensate for changes within the cell wall.