Figure 2. Low histone dosage affects the fertility of rescued adults.

(A) Results of rescue tests for adult flies with different copy numbers of wild-type (WT) histone gene units (His-GUs; 4, 6, 8, 10, 12, 16, and 20 units) that were reintroduced into histone null mutants (His^D) to rescue the lethal phenotype. Results are means ± SD from triplicate determinations.

(B) Western blot analysis of levels of H3, H4, H2A, H2B, and H1 histones in virgin adult flies with 12, 16, or 20 His-GUs, His^D, and WT (w¹¹¹⁸).

(C, D) Results of fertility tests of male (C) and female (D) adult flies with 12, 16, or 20 His-GUs, His^D, and WT (w¹¹¹⁸). The fertility test is done by counting the number of surviving adult progeny produced by male or female flies of the given genotype crossed with w¹¹¹⁸. Each point represents a vial of flies. The horizontal bar indicates the mean number of adult progeny produced. Error bars represent standard error of the mean (± SEM).

(E, F) Testes (E) and ovaries (F) from flies with different histone copy numbers were classified by their morphology into three categories, as show in the top panels: WT (w¹¹¹⁸), moderate defect, and severe defect. Below, the numbers of adults with the given testis (E) and ovary (F) morphology in flies with 12, 16, or 20 His-GUs, His^D, and WT are shown. Total number of dissected testes and ovaries is listed on the right.

See also Figure S2.