A developmentally regulated bud specific transcript in pea has sequence similarity to seed lectins.

We report a striking example of organ and stage specific gene expression in pea (Pisum sativum L.). We have identified a transcript to a previously isolated cDNA clone, pEA207 (WF Thompson et al. (1983) Planta 158: 487-500) which accumulates in the actively growing bud of the pea plant and is either absent or present at very low levels in the expanded leaves below the bud. The deduced amino acid sequence of pEA207 shows 49% similarity to the phytohemagglutinin lectin sequence of kidney bean (Phaseolus vulgaris) (LM Hoffman, DD Donaldson (1985) EMBO J 4: 883-889) and 37% similarity to that of the major pea seed lectin sequence (TJV Higgins et al. (1983) J Biol Chem 258: 9544-9549). It is also similar to seed lectins from five other legumes. All of the residues directly involved in metal binding by lectins are present in this sequence. We discuss the possibility that pEA207 encodes a sugar binding lectin-like polypeptide associated with the cell walls of actively growing plant cells.