Localization of the type I ribosome-inactivating protein, luffin, in adultand embryonic tissues of Luffa cylindrica L-Roem.

The subcellular localization of the type I ribosome-inactivating protein, l uffin, has been investigated by means of immunofluorescence light microscop y. A different pattern of protein distribution has been observed in embryon ic and somatic tissues. In mature seeds luffin is accumulated within protei n bodies in the storage tissue; vacuolar compartmentation in cells of the c otyledonary leaves is maintained during germination of the seedlings. In ad ult tissues, such as mature leaves and stems, the targeting of the protein is different, since luffin is found in the extracellular spaces. This local ization outside the plasma membrane has been confirmed by enzymatic activit y determination on the intercellular fluid present in the apoplastic space, Results on luffin localization are discussed with respect to the putative function(s) of this enzyme.