The identification of theB ^S breakpoint and of two possibleBar genes

Summary

Two coding regions were identified within a 110 kb region which includes all mappedBar breakpoints. Both lie proximal to the identifiedBar breakpoints. The first coding region, designatedBarA, is 5 kb from the most proximalBar mutation,B ⁵⁸¹, and 66 kb from theB ^S breakpoint. It encodes a 1.3 kb transcript, which is found in late third instar larvae but is absent in 1–3-day-old pupae.B ⁱ,R(B) ^hd3,B ^85c1s andB ^S result in overproduction of this transcript in late third instar larvae. A second coding region, which was previously identified asBarH1, maps 18 kb fromB ⁵⁸¹ and 79 kb from theB ^S breakpoint. In third instar larvae, the abundance of theBarH1 transcript is very low in both wild type and variousBar mutatants, with the exception of R(B)^hd3. In 1–3-day-old pupae, the level of theBarH1 transcript is higher.BarH1 was previously identified as theBar gene. However, this report raises the possibility thatBarA rather thanBarH1 is theBar gene or that more than one gene may be involved in Bar position effects.