Characterization and Localization of β-Lectins in Lower and Higher Plants

Abstract

The presence of a class of arabinogalactan proteins, known as β-lectins, as detected by their interaction with the Yariv antigen, has been extended from earlier work (Jermyn and Yeow 1975) to include a number of lower plants. A comparison is made of the amino acid and carbohydrate composition of β-lectins isolated from green leaves and seeds from a number of species. The protein content of the isolated β-lectins from leaves has a range of 3-8%, while those examined from seeds have a more variable protein content. The amino acid compositions of the β-lectins from both leaves and seeds are generally similar, usually with high levels of serine, glycine, alanine and hydroxyproline. The monosaccharide compositions are also similar with an overall range of galactose/arabinose values between 1.3 and 2.8. Trace amounts of fucose, rhamnose, mannose and xylose are often detected.

The β-lectins were localized in various tissues using the Yariv antigen as a histochemical reagent. Intense staining was observed within the secretory canals of both the stem and leaves of Hedera helix. However, the staining of the leaves and petioles of Zantedeschia and Alocasia species was mainly associated with the plasma membrane and the cell wall of the aerenchyma. Specific staining is also reported in the reproductive tissues of Gladiolus and the possible function of the β-lectins is these highly specialised tissues is discussed.