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Full-length cDNA sequences of two exo-β-glucanases, LP-ExoI and LP-ExoII, secreted into cell walls of lily (Lilium longiflorum) pollen tube, were determined by RT-PCR. LP-ExoI exhibited over 80% similarity to LP-ExoII at both DNA and amino acid levels. RT-PCR showed that LP-ExoI transcripts were abundant in pollen grains and tubes, but could not be detected in leaf, stem, stigma, style, ovary, petal, filament, young root, young bud, and scale leaf of bulb. However, LP-ExoII transcripts ubiquitously existed in all the tissues tested. To determine the potential substrates of exo-β-glucanases, cell wall components of lily tissues were analyzed. Linkage analysis revealed that pollen tubes contained high levels of 3-Glc in hemicellulose (44.3%), while pollen grains had no detectable 3-Glc. The hemicellulose fraction of pollen tubes was treated with lichenase and the product was analyzed by HPLC-PAD to determine the origin of 3-Glc. Specific tetra-saccharide was liberated from hemicellulose of pollen tubes, suggesting the presence of 1,3 : 1,4-β-glucan in lily pollen tube hemicellulose. The structure of this 1,3 : 1,4-β-glucan may be different from cereal plant 1,3 : 1,4-β-glucan, since tri-saccharide was not detected in hemicellulose fraction after lichenase treatment. LP-ExoI and LP-ExoII, expressed in pollen grains and tubes, may be involved in the regulation of pollen tube elongation by hydrolyzing callose and 1,3 : 1,4-β-glucan within pollen tube walls. [ABSTRACT FROM PUBLISHER]

Plant cells can monitor alternations in cell wall architecture. Treatment of tobacco BY2 cells with a cellulase or cellulose biosynthesis inhibitor significantly decreased the mRNA of endoxyloglucan transferase (EXGT). Our results indicated the importance of another gene(s) induced by cell wall defects for the decrease in EXGT mRNA. [ABSTRACT FROM PUBLISHER]

When auxin stimulates rapid cell elongation growth of cereal coleoptiles, it causes a degradation of 1,3:1,4-β-glucan in hemicellulosic polysaccharides. We examined gene expressions of endo-1,3:1,4-β-glucanase (EI) and exo-β-glucanase (ExoII), of which optimum pH are about 5, and molecular distribution of hemicellulosic polysaccharides in barley (Hordeum vulgareL.) coleoptile segments treated with or without IAA. IAA (10–5 M) stimulated the gene expression of EI, while it did not affect that of ExoII. IAA induced gene expression of EI after 4 h and increased wall-bound glucanase activity after 8 h. The molecular weight distribution of hemicellulosic polysaccharides from coleoptile cell walls was shifted to lower molecular weight region by 2 h of IAA treatment. Fusicoccin (10–6 M) mimicked IAA-induced elongation growth and the decrease in molecular weight of hemicellulosic 1,3:1,4-β-glucan of coleoptiles in the first 4 h, but it did not promote elongation growth thereafter. These facts suggest that acidification of barley cell walls by IAA action enhances pre-existing cell wall-bound glucanase activity in the early first phase of IAA-induced growth and the late second phase involves the gene expression of EI by IAA. [ABSTRACT FROM PUBLISHER]

A β-D-glucanase activity hydrolyzing 1,3:1,4-β-D-glucan was released from the cell walls of barley by 3M LiCl treatment. It was purified by sequential cation-exchange, gel-filtration and hydrophobic chromatography. The molecular mass of the glucanase was 66 kDa as determined by SDS-polyacrylamide gel electrophoresis. Sequence determination of the first thirty amino acids of the N-terminus revealed a high homology of this enzyme to the Pseudomonas l,4-β-D-glucosidase (56.5%). The purified β-D-glucanase has a pH optimum at 5.0, and hydrolyzes oligosaccharides containing β-D-1,3 or β-D-1,4 linkage. The glucanase showed maximum hydrolytic activity toward laminaritetraose, the rate being about two times that of cellotetraose and about four times that of gentiobiose. Polysaccharides such as lichenan, l,3:l,4-β-D-glucan (from barley), laminarin and pustulan are also hydrolyzed, but not carboxylmethyl-curdlan, carboxymethyl-cellulose, xyloglucan and maltose. The purified β-D-glucanase yielded monomeric glucose from laminarihexaose, and exhibited characteristics of an exo-l,3-β-D-glucanase (EC 3.2.1.58). The activity and biochemical characteristics of this enzyme suggest that it is an exo-l,3-β-D-glucanase involved in the rapid turnover of l,3:l,4-β-D-glucan in barley cell walls during seedling growth. [ABSTRACT FROM AUTHOR]

Quantitative and qualitative changes in cell wall polysaccharides of asparagus (Asparagus officinalis L.) during somatic embryogenesis and plantlet development were determined by methylation analysis. The globular embryos developed from the stable embryogenic calli in suspension culture for 15 d. The embryos developed into plantlets on a solid (2.5% agar) medium in 50 d. The root and other parts were separately sampled from the plantlet for sugar analysis of the cell walls. The percentage of cellulose was maintained at a low level (20%) during somatic embryogenesis and increased in the root and shoot after plantlet development (40–50%), while that of pectic polysaccharides decreased from 45 to 20–30% after embryogenesis. Hemicellulose was maintained at a constant percentage (30–40%) throughout the experiment. Methylation analysis of hemi-celluloses revealed that 5- and 3,5-linked arabinose transiently increased during embryogenesis and then steadily decreased during plantlet development. The contents of 4-linked xylose, the main component of xylan, and 4- and 4,6-linked glucose, found in the glucan backbone of xyloglucans, increased after plantlet development. These results suggested that branched arabinan was actively synthesized in embryonic calli but degraded during the course of differentiation, while xylan and xyloglucan were massively synthesized in the root and shoot as plantlet developed. [ABSTRACT FROM AUTHOR]