Macromolecular trafficking between Nicotiana tabacum and the holoparasite Cuscuta reflexa

Transgenic tobacco plants expressing green fluorescent protein (GFP) under the control of the companion cell-specific promoter, AtSUC2, were parasitiz ed by the holoparasite Cuscuta reflexa (dodder), GFP, moving in the translo cation stream of the host, was transferred to the Cuscuta phloem via the ab sorbing hyphae of the parasite. An identical pattern of transfer was observ ed for the phloem-mobile probe, carboxyfluorescein. Following uptake by the parasite, GFP was translocated and unloaded from the Cuscuta phloem in mer istematic sink tissues. Contrary to published data, these observations sugg est the presence of a functional symplastic pathway between Cuscuta and its hosts, and demonstrate a considerable capacity for macromolecular exchange between plant species.