Defects in protein modification precede developmental defects in l(3)c21RRW630, a temperature-sensitive Drosophila developmental mutant

The temperature-sensitive Drosophila developmental mutation, l(3)c21RRW630 (abbreviated RW630) disturbs oogenesis and has a maternal effect on embryogenesis. At restrictive temperature, RW630 alters post-translational modification of three abundant proteins. To examine the causal relationship between these biochemical defects and the developmental defects in RW630, a series of temperature-shift experiments was performed. It was found that defects in protein modification could be detected in RW630 ovaries after RW630 females had been exposed to restrictive temperature for 1 day. RW630 females treated in this fashion produce embryos which contain a low level of unmodified proteins. Nevertheless, these embryos hatch at a normal rate. Since these ovaries and these embryos are developmentally normal, but do show defects in protein modification, it is unlikely that the RW630 developmental defects cause the biochemical defects in RW630. It is more likely that accumulation of unmodified proteins after extended exposure to restrictive temperature produces the developmental defects in RW630.