Oleosin expression and trafficking during oil body biogenesis in tobacco leaf cells

We have established a versatile method for studying the interaction of the oleosin gene product with oil bodies during oil body biogenesis in plants. Our approach has been to transiently express a green fluorescent protein (GFP)‐tagged Arabidopsis oleosin gene fusion in tobacco leaf cells containing bona fide oil bodies and then to monitor oleosin‐GFP expression using real‐time confocal laser scanning microscopy. We show that normally non‐oil‐storing tobacco leaf cells are able to synthesize and then transport oleosin‐GFP fusion protein to leaf oil bodies. Synthesis and transport of oleosin‐GFP fusion protein to oil bodies occurred within the first 6 h posttransformation. Oleosin‐GFP fusion protein exclusively associated with the endoplasmic reticulum and was trafficked in a Golgi‐independent manner at speeds approaching 0.5 μm sec–1 along highly dynamic endoplasmic reticulum positioned over essentially static polygonal cortical endoplasmic reticulum. Our data indicate that oil body biogenesis can occur outside of the embryo and that oleosin‐GFP can be used to monitor early events in oil body biogenesis in real‐time. genesis 35:125–132, 2003. © 2003 Wiley‐Liss, Inc.