Ferredoxin-NADP+ reductase,a nuclearly-coded enzyme unaffected by tentoxin treatment

Previous studies in our laboratory have shown that tentoxin prevents the incorporation of polyphenol oxidase (PPO), a nuclearly-coded protein, into the chloroplasts of sensitive species. In this study, we show, by comparison of electrophoretically separated isozymes, that ferredoxin-NADP⁺ reductase (FNR) is nuclearly coded in Nicotiana. Electrophoresis of FNR isozymes from tentoxin treated seedlings of a sensitive and a resistant species demonstrated that, unlike PPO, ferredoxin-NADP⁺ reductase was unaffected by tentoxin treatment. These data indicate that tentoxin selectively inhibits transport of cytoplasmically synthesized proteins into the chloroplast, and does not produce a generalized disruption of cellular integration.This research was supported, in part, by funding under cooperative agreement number 58-7B30-3-548, and is published with the approval of the Director of Arkansas Agr. Exp. Stn. Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the US Dep. Agric. or cooperating agencies and does not imply its approval to the exclusion of other products or vendors that may also be suitable.