Figure 2.

Microinjection experiments performed to determine the threshold level of PP2 required to potentiate cell-to-cell movement of coinjected 20-kDa FITC-dextran. PP2 used in these experiments was either purified from cucurbit phloem exudate or expressed in and extracted from E. coli (Inset). In each microinjection series, the level of FITC-dextran was held constant (1 mM) whereas the level of PP2 was serially reduced until fluorescence associated with the FITC-dextran did not move out from the injected cell.