The complex chloroplast of Euglena evolved through secondary endosymbiosis between a trypanosome host and an algal endosymbiont. In Euglena, nuclear-encoded chloroplast proteins are transported to the chloroplast in vesicles via the ER and Golgi as integral membrane proteins. Steven Schwartzbach and co-workers have now reconstituted this transport system in vitro (see p. 1651). The authors preload Golgi membranes with a 35S-labeled precursor of the light-harvesting chlorophyll a/b binding protein, isolate the membranes, mix them with isolated chloroplasts and track precursor import by following its proteolytic processing in the chloroplast. They show that Golgi-to-chloroplast transport requires light, ATP and GTP but not N-ethylmaleimide-sensitive factor, which indicates that the SNARE proteins common in other vesicle-trafficking pathways are not used. They also uncover information about the signals in Euglena chloroplast protein presequences that are required for plastid import and conclude that during its evolution Euglena developed a novel vesicle-targeting system...

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