Feasibility of using atmospheric pressure matrix-assisted laser desorption/ionization with ion trap mass spectrometry in the analysis of acetylated xylooligosaccharides derived from hardwoods and Arabidopsis thaliana

The atmospheric pressure matrix-assisted laser desorption/ionization with ion trap mass spectrometry (AP-MALDI-ITMS) was investigated for its ability to analyse plant-derived oligosaccharides. The AP-MALDI-ITMS was able to detect xylooligosaccharides (XOS) with chain length of up to ten xylopyranosyl residues. Though the conventional MALDI–time-of-flight/mass spectrometry (TOF/MS) showed better sensitivity at higher mass range (>m/z 2,000), the AP-MALDI-ITMS seems to be more suitable for detection of acetylated XOS, and the measurement also corresponded better than the MALDI-TOF/MS analysis to the actual compositions of the pentose- and hexose-derived oligosaccharides in a complex sample. The structures of two isomeric aldotetrauronic acids and a mixture of acidic XOS were elucidated by AP-MALDI-ITMS using multi-stages mass fragmentation up to MS³. Thus, the AP-MALDI-ITMS demonstrated an advantage in determining both mass and structures of plant-derived oligosaccharides. In addition, the method of combining the direct endo-1,4-β-d-xylanase hydrolysis of plant material, and then followed by AP-MALDI-ITMS detection, was shown to recognize the substitution variations of glucuronoxylans in hardwood species and in Arabidopsis thaliana. To our knowledge, this is the first report to demonstrate the acetylation of glucuronoxylan in A. thaliana. The method, which requires only a small amount of plant material, such as 1 to 5 mg for the A. thaliana stem material, can be applied as a high throughput fingerprinting tool for the fast comparison of glucuronoxylan structures among plant species or transformants that result from in vivo cell wall modification.     

Identification and expression analysis of genes encoding putative cellulose synthases (CesA) in the hybrid aspen, Populus tremula (L.) × P. tremuloides (Michx.)

Cellulose is synthesized in plant cell walls by large membrane-bound protein complexes proposed to contain several copies of the catalytic subunit of the cellulose synthase, CesA. Here we report identification of 10 distinct CesA genes within a database of 100,000 ESTs of the hybrid aspen, Populus tremula (L.) × P. tremuloides (Michx.). Expression analyses in normal wood undergoing xylogenesis and in tension wood indicate xylem specific expression of four putative CesA isoenzymes, PttCesA1, PttCesA3-1, PttCesA3-2 and PttCesA9. Both the protein sequences and the expression profiles of PttCesA3-1 and PttCesA3-2 are very similar, and they may thus represent redundant copies of an enzyme with essentially the same function. Further, one of the generally more constitutively expressed CesA genes, PttCesA2, seems to be activated on the opposite side of a tension wood induced stem, while PttCesA6 appears to be more specific for leaf tissues. The rest of the hybrid aspen CesA genes were found to be relatively evenly expressed over the poplar tissues hereby studied.     

On <Emphasis Type="Italic">g</Emphasis>-functions for Laguerre function expansions of Hermite type

We examine weighted L ^p boundedness of g-functions based on semigroups related to multi-dimensional Laguerre function expansions of Hermite type. A technique of vector-valued Calderón–Zygmund operators is used.