Antiglycan antibodies and lectins are widely used in glycan analysis because their specificities enable them to discriminate among a variety of glycan structures and their multivalency ensures high-affinity binding to the glycans and cell surfaces containing those glycans. This chapter describes the variety of commonly used antibodies and lectins and the types of analyses to which they may be applied.

Chitin oligosaccharidic signals play important roles in plant defense and the initiation of symbiotic interactions of plants with microorganisms. Two of these symbioses which have great agricultural importance are the symbiosis of arbuscular mycorrhizal fungi with about 80% of land plants that leads to the facilitation of nutrient absorption and the host/strain specific nitrogen‐fixing symbiosis between rhizobial strains of bacteria and leguminous plants. Similarities in structures of the Myc factor and Nod factor signals that initiate these two respective symbioses as well as some common features of the early stages of these symbioses have suggested that the rhizobium‐legume symbiosis may have evolved from the more ancient mycorrhizal symbiosis by gene duplication and divergence. This possibility is supported by our recent transgenic studies in which inhibition of expression of a Nod factor‐binding protein in legume roots inhibited both of these symbioses. The above Nod factor‐binding protein represents a new category of lectins ( LNP s) that have both L ectin and N ucleotide P hosphohydrolase activity. These LNPs are members of the apyrase family of enzymes which are found in a wide variety of organisms. Phylogenetic comparisons have shown that the above LNP, (LNP1), represents a unique subcategory of apyrases found in leguminous plants. LNP1 is a peripheral membrane protein localized on the surface of root hairs in the nodulation zone of the root. Using a combination of biochemical, molecular and cell biological techniques we identified a number of other apyrases in the tissues of the legume, Dolichos biflorus, several of which bind to the hog blood group A + H gastric mucin affinity resin used in the isolation of LNP1. We now report the comparison of these LNPs with respect to their structures, carbohydrate‐ and nucleotide‐binding activities and differential expression in the plant. Phylogenetic analysis shows that these other LNPs are not confined to leguminous plants. The data suggest that these LNPs may function as co‐receptors or modulators of other chitin‐related oligosaccharide signaling events found in plants. Support or Funding Information This research was supported by NIH Grant GM21882 and by Ceres, Inc.

The glycan symbol nomenclature proposed by Harvey et al. in these pages has relative advantages and disadvantages. The use of symbols to depict glycans originated from Kornfeld in 1978, was systematized in the First Edition of "Essentials of Glycobiology" and updated for the second edition, with input from relevant organizations such as the Consortium for Functional Glycomics. We also note that > 200 illustrations in the second edition have already been published using our nomenclature and are available for download at PubMed.

Nodulation in legumes requires the recognition of rhizobially made Nod factors. Genetic studies have revealed that the perception of Nod factors involves LysM domain receptor-like kinases, while biochemical approaches have identified LECTIN NUCLEOTIDE PHOSPHOHYDROLASE (LNP) as a Nod factor-binding protein. Here, we show that antisense inhibition of LNP blocks nodulation in Lotus japonicus. This absence of nodulation was due to a defect in Nod factor signaling based on the observations that the early nodulation gene NODULE INCEPTION was not induced and that both Nod factor-induced perinuclear calcium spiking and calcium influx at the root hair tip were blocked. However, Nod factor did induce root hair deformation in the LNP antisense lines. LNP is also required for infection by the mycorrhizal fungus Glomus intraradices, suggesting that LNP plays a role in the common signaling pathway shared by the rhizobial and mycorrhizal symbioses. Taken together, these observations indicate that LNP acts at a novel position in the early stages of symbiosis signaling. We propose that LNP functions at the earliest stage of the common nodulation and mycorrhization symbiosis signaling pathway downstream of the Nod factor receptors; it may act either by influencing signaling via changes in external nucleotides or in conjunction with the LysM receptor-like kinases for recognition of Nod factor.

This chapter provides an overview of naturally occurring glycan-binding proteins (GBPs), the history of their discovery, some of their biological functions, ways in which GBPs are identified, and challenges in defining their biologically relevant ligands. The chapters that follow describe the analysis of glycan–protein interactions (Chapter 29), the physical principles involved (Chapter 30), and the structures and biological functions of important subclasses of GBPs (Chapters 31–38).

This chapter provides an overview regarding naturally occurring glycan-binding proteins (GBPs), with an emphasis on their discovery and current classification schemes. Some general principles regarding the structure and function of GBPs are also considered, as well as aspects of their glycan-binding properties. Further information regarding most of the major classes of GBPs can be found in Chapters 28–35. For details regarding the analysis of glycan–protein interactions and the physical principles involved, see Chapter 27.