cDNA Cloning of a Novel Lectin-Like Xylem Sap Protein and Its Root-Specific Expression in Cucumber

: A novel cDNA encoding a major 30-kDa protein in xylem sap of cucumber Cucumis sativus (XSP30) was homologous to the B chains of galactose-binding lectins such as ricin and abrin. XSP30 gene was specifically expressed in roots, and XSP30 was immunologically detected only in the xylem sap, but not in any organs.