The Gastrodia Antifungal Protein (GAFP-1) and Its Transcript Are Absent from Scions of Chimeric-grafted Plum

Abstract

The Gastrodia antifungal protein (GAFP-1) is a monocot mannose-binding lectin found in the Asiatic orchid Gastrodia elata. Transgenic plum (Prunus domestica var. ‘Stanley’) lines (4J and 4I) expressing GAFP-1 exhibit enhanced disease resistance to the stramenopile pathogen Phytophthora cinnamomi and the root-knot nematode Meloidogyne incognita. Rootstocks created from such transgenic lines might be more readily accepted by consumers if it can be shown that foreign gene products are not migrating into a grafted, nontransgenic scion on which fruit is produced. In this study, wild-type (WT) plum tissue was budded onto transgenic plum lines 4J and 4I to create chimeric-grafted trees. Tissues from chimeric-grafted trees were analyzed for gafp-1 transcripts (leaf and root) and protein (leaf, soft shoot, and root) by reverse transcription–polymerase chain reaction and immunodetection, respectively. Transcripts of gafp-1 were detected consistently in the root tissues but not within the leaves of the grafted, WT scions. Similarly, the GAFP-1 lectin was identified within the roots, but not in the soft shoot or leaf tissues of the grafted, WT scions. These results suggest that gafp-1 mRNA and protein are not moving into the WT scion tissues of chimeric-grafted plum trees.