Voltage gradients and microtubules both involved in intercellular protein and mitochondria transport in the telotrophic ovariole of Dysdercus intermedius

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Abstract
In the telotrophic ovariole of Dysdercus intermedius the intercellular transport consists of different subsystems. Microinjection of FITC-labeled slowly diffusing proteins with opposite electrical net charges and of mitochondria was used to study the translocation of macromolecules and organelles. a) By intracellular measurements a voltage gradient of about 4 mV between the tropharium as the more negative side and the previtellogenic oocytes could be demonstrated. b) After injection into the tropharium negatively charged proteins migrated according to the electropotential gradient via the trophic cords into the oocytes. Positively charged proteins, however, were retained in the tropharium. c) After injection into previtellogenic oocytes both negatively and positively charged proteins moved into the trophic cords. Thus, the effectiveness of the electropotential gradient on the distribution of charged proteins is more pronounced from the tropharium side. d) Mitochondria microinjected into the trophic core were probably aligned along microtubules and translocated towards the trophic cords. — These results suggest that in the telotrophic bug ovariole a number of intercellular transport subsystems contribute to provide previtellogenic oocytes with nurse cells products. An electrophoretic transport mechanism for soluble proteins acting especially within the tropharium and a microtubule-associated transport for mitochondria could be evidenced.