A Nod factor-binding lectin is a member of a distinct class of apyrases that may be unique to the legumes

Recent studies from our laboratory have found that a root lectin from the l egume Dolichos biflorus is present on the root surface, binds rhizobial Nod factor and has apyrase activity. To assess the broader significance of thi s lectin/nucleotide phosphohydrolase (Db-LNP), we have cloned a second rela ted cDNA (Db-apyrase-2) from D. biflorus, as well as related cDNAs from the legumes Lotus japonicus and Medicago sativa, and from Arabidopsis thaliana , a non-legume. The deduced amino acid sequences of these apyrases were ali gned with one another and with the sequences of other apyrases from plants, animals, yeast and protozoa. Phylogenetic analysis shows that Db-LNP has c losely related orthologs only in other legumes, while Db-apyrase-2 is more closely related to apyrase sequences from non-leguminous plants. We also sh ow that the orthologs of Db-LNP from M. sativa and Pisum sativum have carbo hydrate binding activity. The results suggest that legume LNPs may represen t a special class of apyrases that arose by gene duplication and subsequent specialization.