Fig 1. HP1b¹⁶ and HP1b ⁸⁶ are null alleles.

A. Top—diagram showing the genomic region near the HP1b locus on the X chromosome. The P element mobilized to generate the HP1b alleles is indicated by a triangle above the genes shown in blue above the position on the X chromosome (bp). Black arrows mark the primers used to screen for deletions. Bottom—close-up of HP1b with the three deletion alleles shown below. All three deletions remove the HP1b start codon. B. RT-PCR analysis shows that full-length HP1b mRNA is transcribed in wildtype OR embryos, but not in HP1b¹⁶ or HP1b⁸⁶ homozygous embryos. CG7346 and APC4 are transcribed in all samples, as is the Rpl32 positive control. RT: reverse transcriptase. C. No HP1B protein is detected in HP1b¹⁶ and HP1b⁸⁶ homozygous larvae (left panel; *); Actin (right panel; **) serves as loading control.