CHARACTERIZATION AND EVOLUTIONARY RELATIONSHIPS OF MAGNOLIA LEGUMIN-ENCODING CDNAS REPRESENTING 2 DIVERGENT GENE SUBFAMILIES

We have cloned and sequenced three different cDNAs encoding legumins of Magnolia salicifolia. Analysis of the nucleotide and derived amino acid sequences shows that the cDNAs designated A2, A11, and B14 represent two divergent subfamilies with nucleotide similarities of only about 55%. The B14 cDNA codes for a relatively methionine-rich legumin precursor, and the beta-chain of this protein is shown to be glycosylated; neither feature is common in legumins. In an evolutionary analysis, the B14 legumin cDNA is relatively similar to gymnospermous legumin sequences and paralogous to all angiosperm legumins hitherto known. The A legumin sequence clusters with those of monocot legumins in a low angiosperm branch. We conclude that the evolution of legumin genes in angiosperms involved an early gene duplication which resulted in the progenitor of the B14 legumin, on the one hand, and the progenitor of A2, A11 and modern angiosperm legumins, on the other hand.