Drosophila melanogaster Importin 1 and 3 Can Replace Importin 2 During Spermatogenesis but Not Oogenesis

Corresponding author: David S. Goldfarb, University of Rochester, Rochester, NY 14627., dasg{at}mail.rochester.edu (E-mail)

Communicating editor: K. V. ANDERSON

Importin 's mediate the nuclear transport of many classical nuclear localization signal (cNLS)-containing proteins. Multicellular animals contain multiple importin genes, most of which fall into three conventional phylogenetic clades, here designated 1, 2, and 3. Using degenerate PCR we cloned Drosophila melanogaster importin 1, 2, and 3 genes, demonstrating that the complete conventional importin gene family arose prior to the split between invertebrates and vertebrates. We have begun to analyze the genetic interactions among conventional importin genes by studying their capacity to rescue the male and female sterility of importin 2 null flies. The sterility of 2 null males was rescued to similar extents by importin 1, 2, and 3 transgenes, suggesting that all three conventional importin 's are capable of performing the important role of importin 2 during spermatogenesis. In contrast, sterility of 2 null females was rescued only by importin 2 transgenes, suggesting that it plays a paralog-specific role in oogenesis. Female infertility was also rescued by a mutant importin 2 transgene lacking a site that is normally phosphorylated in ovaries. These rescue experiments suggest that male and female gametogenesis have distinct requirements for importin 2.

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