LECTINS OF MEMBERS OF THE AMARYLLIDACEAE ARE ENCODED BY MULTIGENE FAMILIES WHICH SHOW EXTENSIVE HOMOLOGY

Screening of complementary DNA (cDNA) libraries constructed from poly(A) rich RNA isolated from young developing ovaries of Narcissus cv. Fortune and Hippeastrum hybr. resulted in the isolation of multiple lectin cDNA clones. Although the lectin clones show a high degree of overall homology within their coding region, they clearly differ from each other at some positions in their nucleotide sequence and deduced amino acid sequence. Moreover, since some differences in the sequence result in different charges along the lectin polypeptides, the different cDNA clones encode lectins with different isoelectric points, which explains the occurrence of multiple lectin isoforms in Narcissus and Hippeastrum at the molecular level. Furthermore, Southern blot analysis of genomic DNA isolated from Narcissus and Hippeastrum yielded numerous restriction fragments hybridizing with lectin cDNA probes leaving no doubt that the Narcissus and Hippeastrum lectins, like the Galanthus nivalis lectin, are encoded by families of closely related lectin genes.