laminaran and laminarihexaose

Plants survey their environment for the presence of potentially harmful or beneficial microbes. During colonization, cell surface receptors perceive microbe-derived or modified-self ligands and initiate appropriate responses. The recognition of fungal chitin oligomers and the subsequent activation of plant immunity are well described. In contrast, the mechanisms underlying β-glucan recognition and signaling activation remain largely unexplored. Here, we systematically tested immune responses towards different β-glucan structures and show that responses vary between plant species. While leaves of the monocots Hordeum vulgare and Brachypodium distachyon can recognize longer (laminarin) and shorter (laminarihexaose) β-1,3-glucans with responses of varying intensity, duration and timing, leaves of the dicot Nicotiana benthamiana activate immunity in response to long β-1,3-glucans, whereas Arabidopsis thaliana and Capsella rubella perceive short β-1,3-glucans. Hydrolysis of the β-1,6 side-branches of laminarin demonstrated that not the glycosidic decoration but rather the degree of polymerization plays a pivotal role in the recognition of long-chain β-glucans. Moreover, in contrast to the recognition of short β-1,3-glucans in A. thaliana, perception of long β-1,3-glucans in N. benthamiana and rice is independent of CERK1, indicating that β-glucan recognition may be mediated by multiple β-glucan receptor systems.

Topics: Arabidopsis; beta-Glucans; Brachypodium; Capsella; Glucans; Hordeum; Nicotiana; Oligosaccharides; Plant Immunity; Plant Leaves; Plant Proteins; Receptors, Immunologic; Species Specificity

Endo-1,3-β-glucanases derived from marine mollusks have attracted much attention in recent years because of their unique transglycosylation activity. In this study, a novel endo-1,3-β-glucanase from the scallop

Topics: Amino Acid Sequence; Animals; Cloning, Molecular; Glucan Endo-1,3-beta-D-Glucosidase; Glucans; Glycosylation; Hydrolysis; Oligosaccharides; Pectinidae; Recombinant Proteins; Structure-Activity Relationship; Substrate Specificity

A full characterization of the high-resolution NMR spectrum of the laminarihexaose is described and used for the determination of the binding epitope of the more complex but structurally related laminarin. These biophysical data extend the current knowledge of β-glucans/Dectin-1 interactions and suggest different biological mechanisms in close relation with the size of the saccharidic chain.

Topics: beta-Glucans; Binding Sites; Carbohydrate Sequence; Epitope Mapping; Glucans; Humans; Immunologic Factors; Lectins, C-Type; Macrophage-1 Antigen; Magnetic Resonance Spectroscopy; Membrane Proteins; Models, Molecular; Molecular Sequence Data; Nerve Tissue Proteins; Oligosaccharides; Polysaccharides; Protein Binding; Recombinant Proteins; Structure-Activity Relationship

The synthesis of laminarahexaose is described. NMR studies of several of the intermediates leading to the beta-1,3-glucan show anomalously small coupling constants for some of the C-1 hydrogens. An X-ray structure for the protected hexasaccharide shows that the small coupling constants are due to some of the glucopyranose rings adopting a twist-boat conformation. The X-ray studies also explain other unexpected NMR observations.

Topics: beta-Glucans; Carbohydrate Conformation; Carbohydrate Sequence; Magnetic Resonance Spectroscopy; Models, Molecular; Molecular Structure; Oligosaccharides