Capacity of P transgenes to induce Trans-Silencing Effect.

A large panel of transgenes inserted at various chromosomal locations has been tested for its capacity to induce TSE. Females from lines carrying the tested transgene were crossed with males carrying a BQ16 or P-Co1 transgene as target. M females (from the Cantony or w1118 strains, devoid of P sequences) were crossed with similar males in the same conditions (M control). Overnight lacZ staining of ovaries was performed. Tested transgenes were designated as ��Silencer�� when progeny showed egg chambers with lacZ repression when compared to the M control progeny. Transgenes known to be flanked by TAS are indicated by an asterix; telomeric transgenes inserted in terminal retrotransposons are indicated by two asterixes. Insertions located in the region of the 2L chromosomal arm which is covered by HP1 on larval polytene chromosomes (called the ��gooseneck��) are indicated by G. Among silencers, R indicates that the effect was described previously in [44]; P-1155 was not found to be a repressor in the latter study, whereas we identified it as a silencer possibly because we used a more sensitive target transgene. Tested transgenes are P-lacZ constructs except for those of the SUPor-P series which are P-white-yellow and for P-833 and P-819 which are P-white-rosy constructs. All SUPor-P insertions were tested using P-Co1 as a target so that the two transgenes share long enough sequence homology (white marker). The cytological location is given in parenthesis. P-lac-w clusters correspond to transgenes in tandem arrays; the number of transgenes is given in parenthesis; X-ray indicates that the line has undergone a chromosomal rearrangement �C for details, see [51], 55. Chromosome 1 = 1A�C20F; 2L arm = 21A�C40F ; 2R arm = 41A�C60F; 3L arm = 61A�C80F; 3R arm = 81A�C100F; chromosome 4 = 101A�C102F; the telomeres are in bold. The properties and references of all transgenes are listed in Table S2. Mapping and orientation of some telomeric insertions inside a TAS repeat are reported in Figure S1.