Comparison of plant samples at the metabolome level using pattern recognition analysis of analytical spectra

Abstract

Comparison of various plant samples at the metabolome level using pattern recognition analysis of analytical spectra (pyrolysis mass spectrometry, fourier transform infrared spectroscopy, and proton nuclear magnetic resonance spectroscopy) was achieved. Pyrolysis mass spectrometry (PyMS) is a rapid, simple, high-resolution analytical method based on thermal degradation of complex material in a vacuum and has been widely applied to the discrimination of closely related microbial strains. Also fourier transform infrared spectroscopy (FTIR) provides biochemical profiles containing overlapping signals from a majority of the compounds present when whole cells are analyzed. Leaf samples of seven higher plant species and varieties were subjected to PyMS and FTIR. Principal component analysis (PCA) of PyMS data was not able to discriminate these plants in discrete clusters. However, canonical variate analysis of PyMS data separated these plants from one another. A hierarchical dendrogram based on canonical variate analysis was in agreement with the known taxonomy of the plants at the variety level. These results indicate that PyMS is able to discriminate higher plants based on taxonomic classification at the family, genus, species, and variety level. Like PyMS, a hierarchical dendrogram based on PCA of FTIR data showed relationships between plants that was in agreement with known plant taxonomy. Genetic programming analysis determined the top three to five biomarkers from FTIR data that discriminated plants at each hierarchical level of the dendrogram. Most biomarkers determined by GP analysis at each hierarchical level were specific to the carbohydrate fingerprint region ($1200-800cm^{-1}$) of the FTIR spectrum. Differences in cell wall composition and structure can provide the basis for chemotaxonomy of higher plants as our results indicate that discrimination of higher plant species and varieties by FTIR reflects the known phylogenetic relationships between plants. ...