Figure 2.

Fluorescence micrographs of tobacco callus cells transformed with Sig-(Ser-Pro)₃₂-EGFP (A) or Sig-(GAGP)₃-EGFP (B); (C) nontransformed tobacco callus cells. The synthetic genes encoded a signal sequence to direct the products through the endoplasmic reticulum and Golgi, then out to the extracellular matrix (51). Not shown are cells transformed with Sig-EGFP, which looked like those in A and B; however, the medium fluorescence was much less intense. The fluorescence in these highly vacuolated, cultured cells surrounds the nuclei but is not inside of them, judging by optical sections (not shown). The microscope was a Molecular Dynamics Sarastro 2000 confocal laser scanning microscope with a 488-nm laser wave length filter, a 510-nm primary beam splitter, and a 510-nm barrier filter.