Mitochondria morphology is a dynamic process regulated by competing fission and fusion components. In an attempt to identify novel proteins responsible for mitochondria morphology, an RNAi screen was performed using Drosophila S2 cells (Yaffe, unpublished). One candidate produced from this screen is parcas. S2 cells treated with dsRNA for multiple regions of parcas display a significant increase in either general mitochondrial fragmentation or mitochondria that are fragmented into aggregated balls. Microscopy and biochemical characterization of the Parcas protein indicates that the protein localizes to the mitochondria. The effect on the mitochondria in the RNAi experiments supports a role in mitochondria morphology, most likely fusion due to the fragmented phenotype, while the association of Parcas with the mitochondria suggests that this role is fairly direct. The nature of this role, however, remains to be seen.

RNA localization is an important regulator of protein expression during Drosophila development. Trailer Hitch and Cup are protein components of a RNP complex that mediates RNA localization events during embryogenesis. These RNP complexes localize in particles that line the surface of the ER, or are occasionally seen in small, mobile particles. A previous study has determined that assembly of Exu, another component of this complex, into particles requires intact microtubules. Here, we demonstrate that disruption of the microtubules also results in a reduction of Tral particles, as well as completely immobilizing all Tral particles within live egg chambers. Abnormal Cup particle formation is also observed.