Characterization of the Plant Cell Wall Response to Isoxaben induced Cell Wall Damage

Abstract

Cell wall damage (CWD) causes extensive changes in cell wall composition and structure, which seem to be mediated by a cell wall integrity signalling mechanism. Though parallels have been found to the cell wall integrity signalling pathway in yeast, it is clear that a more detailed study in plants is necessary to understand the process in detail. Classical induction of CWD (pathogens, stress, foraging animals) is often local, or overlaps with other response systems and has rarely been studied specifically. Treating Arabidopsis thaliana seedlings with isoxaben (a specific CESA3 and 6 inhibitor) allows the induction of highly specific CWD in growing tissues. Cross-referencing the genes which respond to isoxaben induced CWD with publically available tissue expression data allow identification of genes of interest. Based on this analysis, 108 genes were identified, and KO insertion lines isolated to assign a biological function to the individual candidate gene. 24 of these genes have been characterised both with and without CWD induction in this PhD. Genes of particular interest were picked using a FTIR clustering method. This method identified genes for which the insertions changed the response to isoxaben and genes which have a different cell wall composition from the outset. Modified cell wall composition of mutants was confirmed using chemical assays and lignin staining for the 10 selected genes. Of these, 6 genes had substantial mutant phenotypes. Saccharification assay showed high sugar yields for more than 50% of the candidates, in seedlings and stems. The specific cell wall features which lead to this improvement in saccharification have yet to be established.