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Rhamnogalacturonan II (RG-II) is a region of pectin macromolecules that is present in plant primary cell walls. RG-II can be solubilized from cell walls as a borate-RG-II complex (B-RG-II), where two RG-II fragments are cross-linked via a borate diester linkage. Here, a rabbit monoclonal antibody against B-RG-II was prepared, which recognized both B-RG-II and RG-II monomers without borate ester-crosslinking. A pectic fragment with unknown structure was also recognized by the antibody, but neither homogalacturonan nor rhamnogalacturonan I was recognized. Immunoelectron microscopic analyses of Arabidopsis root tip cells were performed using this antibody. The signal was detected in developing cell plates and cell walls, which were denser in longitudinal walls than in transverse walls. These results coincide with our previous results obtained in suspension cultured tobacco cells, confirming that RG-II is present in cell plates at an early stage of their assembly. Abbreviations: B: boron; B-RG-II: borate-RG-II complex; ELISA: enzyme-linked immunosorbent assay; IgG: immunoglobulin G; mBSA: methylated bovine serum albumin; PGA: polygalacturonic acid; PLL: poly-l-lysine; RG-I: rhamnogalacturonan I; RG-II: rhamnogalacturonan II

A comprehensive understanding of the structure and properties of gramineous lignocelluloses is needed to facilitate their uses in biorefinery. In this study, lignocelluloses from fractionated internode tissues of two taxonomically close species, Erianthus arundinaceus and sugarcane (Saccharum spp.), were characterized. Our analyses determined that syringyl (S) lignins were predominant over guaiacyl (G) or p-hydroxyphenyl (H) lignins in sugarcane tissues; on the other hand, S lignin levels were similar to those of G lignin in Erianthus tissues. In addition, tricin units were detected in sugarcane tissues, but not in Erianthus tissues. Distributions of lignin inter-monomeric linkage types were also different in Erianthus and sugarcane tissues. Alkaline treatment removed lignins from sugarcane tissues more efficiently than Erianthus tissues, resulting in a higher enzymatic digestibility of sugarcane tissues compared with Erianthus tissues. Our data indicate that Erianthus biomass displayed resistance to alkaline delignification and enzymatic digestion.

Candida boidinii is a methylotrophic yeast that grows well on oleic acid, D-alanine, or methanol as sole carbon sources. All of these growth substrates induce peroxisomal proliferation; we refer to them as PICs (Peroxisome Inducing Carbon sources). While the activity of catalase, an important peroxisomal enzyme, was induced by all the PICs, peroxisomal oxidases were induced in a PIC-specific manner. To better understand peroxisomal proliferation, two mutant strains that completely lost the ability to grow on all of the PICs were isolated and analyzed. Peroxisome matrix enzymes (catalase, D-amino acid oxidase, alcohol oxidase, etc.) in both mutant strains were mislocalized to the cytosol, and they were active there. Electron microscopy revealed the lack of normal large methanol-induced peroxisomes. We conclude that these mutants are impaired in peroxisomal assembly. Furthermore, the two mutants differed in the catabolite inactivation response to glucose. Finally, although both mutant strains could not grow...

An antisense gene for Aralia cordata cinnamyl alcohol dehydrogenase (CAD) was introduced into tobacco plants. Two transgenic plants showed 55 and 20% reduction of the CAD activity comparedto that of the control plant. Lignin content measured by the acetyl bromide method showed no significant differences between these plants and the control plant. However, the content of p-hydroxycinnamaldehydegroups in lignin was higher in the transgenic than in the control plants. The increase of p-hydroxycinnamaldehydegroups correlated inversely with the levels of CAD activity. Phloroglucinol staining of transverse sections of stem internode indicated that the fiber secondary wall reacted more strongly with the reagentin the transgenic plants. These results suggested that suppression of CAD activity in tobacco plants results in an increase of cinnamaldehyde groups in lignin, but no significant change in lignin content.