Figure 8.

Substrate-Dependent Import of pPORA-GFP into Chloroplasts of Cotyledons of Intact Plants.

(A) PORA-GFP and PORB-GFP were expressed in light-grown wild-type seedlings as chimeric fusion proteins in which the transit sequences of pPORA (pA) and pPORB (pB) were exchanged and fused reciprocally to the mature mPORB-GFP and mPORA-GFP, respectively.

(B) The transit peptide of pPORA makes the import of PORB-GFP dependent on Pchlide, such that this fusion protein no longer accumulates in chloroplasts (pAmPORB). Conversely, the signal sequence of pPORB permits the accumulation of PORA-GFP in the chloroplasts in the absence of Pchlide (pBmPORA). As controls, the uptake of nonmodified pPORB-GFP and pPORA-GFP in chloroplasts of light-grown seedlings was monitored (pPORA and pPORB). Bar = 5 μm.