Figure 1 |. Germline is the major cell type origin of piRNA sexual dimorphism in D. mel gonads.
(A) Genotype and phenotype of males and females that can be identified with definite chromosome content, employing an X chromosome lacking y and w genes as well as a Y chromosome that carries the wildtype y+ and w+ genes.
(B) Comparison of the abundance of piRNAs targeting individual transposon families in XY testis versus XX ovary, normalized to the expression of 20A piRNAs. Sex-biased transposon-targeting piRNAs are color coded and listed on the right.
(C) Comparison of the expression of major piRNA loci in the genome5 in XY testis versus XX ovary, normalized to the expression of 20A piRNAs. Each locus is marked by a different color.
(D) Illustration of the experimental strategy to isolate somatic piRNAs in the gonad. Left: cartoon showing the cell type composition of testis and ovary, with germline having a blue outline and gonadal somatic cells having a red outline. Both germline and gonadal somatic cells express Piwi, which is marked by yellow. Right: cartoon showing Piwi expression in testis and ovary upon efficient, germline-specific knock-down of piwi that completely depletes Piwi in the germline, leaving the somatic cells as the only source of Piwi in the gonad. Gonadal somatic piRNAs are isolated by immunoprecipitating Piwi from these gonads that lose germline Piwi.
(E) UCSC genome browser view of the flamenco piRNA locus showing flamenco piRNAs take up similar fractions of gonadal somatic piRNAs in testis and ovary with similar coverage profiles.
(F) Comparison of the abundance of transposon-antisense piRNAs in testicular and ovarian soma, normalized to the expression of flamenco piRNAs. Sex-biased piRNAs are color coded in the same way as in (B) and the correlation coefficients are reported.
(G) Comparison of the expression of different piRNA loci in testicular and ovarian soma, normalized to the expression of flamenco piRNAs. Sex-biased piRNAs are color coded in the same way as in (B) and the correlation coefficients are reported.
(H) UCSC genome browser view of the 77B piRNA locus, showing its flanking protein-coding genes, its transposon contents and piRNA coverage profiles in two sexes. Note the difference in y-axis scales that reflects a higher relative activity of 77B in the testicular soma than the female counterpart. A putative promoter marked by an RNA pol II peak likely drives the expression of piRNAs from the plus strand that are antisense to two transposons, 176 and idefix.
See also Figure S1.