7-01: Surface characterization of transgenic poplar by TOF-SIMS

Lignocellulosic biomass with the application of genetic engineering is considered as a promising way to reduce biomass recalcitrance resulted in higher conversion yield of biomass to ethanol product.  For example, a membrane-bound cellulase (Korrigan) is a necessary for cellulose biosynthesis and transgenic poplar with overexpression of Korrigan (KOR) gene in Arabidopsis decreases the crystallinity of cellulose recently reported by Takahashi et al. (Plant and Cell Physiology 2009, 50 (6), 1099).  However, it is not fully understood that chemical and physical changes in cell wall microstructure upon the genetic application.  Herein, we’ve applied imaging mass spectrometry (IMS) using time-of-flight secondary ion mass spectrometry (TOF-SIMS) in order to explore the lateral distribution of the major components (e.g. cellulose and lignin) in a transgenic poplar sample.  TOF-SIMS can provide to achieve the molecular mapping images of cellulose and/or lignins on the surface of poplar stem and their semi-quantitative variations (e.g. S/G ratio).  Compared with bulk data (e.g. sugar profile and S/G ratio), the surface data can show the regional specificities in microarea of poplar stem.  For example, site-specific S/G ratios showed 0.87~1.47 while bulk S/G ratio marked as 1.3; the vessel walls gave lower S/G ratios, whereas S/G ratios of fiber walls were relatively higher.  Scanning electron microscope (SEM) showed the morphological differences between control and transgenic poplar stem.  Surface characterization by IMS partially contributes to understand the effect of the genetic manipulation into the cell wall chemical structure related to the recalcitrance of biomass.