A rapid method to screen for cell-wall mutants using discriminant analysisof Fourier transform infrared spectra

We have developed a rapid method to screen large numbers of mutant plants f or a broad range of cell wall phenotypes using Fourier transform infrared ( FTIR) microspectroscopy of leaves. We established and validated a model tha t can discriminate between the leaves of wildtype and a previously defined set of cell-wall mutants of Arabidopsis. Exploratory principal component an alysis indicated that mutants deficient in different cell-wall sugars can b e distinguished from each other. Discrimination of cell-wall mutants from w ild-type was independent of variability in starch content or additional unr elated mutations that might be present in a heavily mutagenised population. We then developed an analysis of FTIR spectra of leaves obtained from over 1000 mutagenised flax plants, and selected 59 plants whose spectral variat ion from wildtype was significantly out of the range of a wild-type populat ion, determined by Mahalanobis distance. Cell wall sugars from the leaves o f selected putative mutants were assayed by gas chromatography-mass spectro metry and 42 showed significant differences in neutral sugar composition. T he FTIR spectra indicated that six of the remaining 17 plants have altered ester or protein content. We conclude that linear discriminant analysis of FTIR spectra is a robust method to identify a broad range of structural and architectural alterations in cell walls, appearing as a consequence of dev elopmental regulation, environmental adaptation or genetic modification.