Expression and localization of the UNO fragments UNO_N-, UNO_M- and UNO_C-EGFP in spermatocytes.

(A) The driver bamP-GAL4-VP16 was used for expression of the indicated UASt transgenes in an uno+ background. Testis squash preparations for comparison of expression level and pattern were labeled with a DNA stain. Apical testes regions are displayed. The images presenting merged DNA and EGFP channels (top row) are shown with identical settings during acquisition and display, indicating that expression levels were maximal in case of UNO_M-EGFP, weaker for UNO_N-EGFP and considerably weaker for UNO_C-EGFP. In case of the images displaying only the EGFP signals in grey values (bottom row), display settings were enhanced in case of UNO_C-EGFP to reveal its weak expression. (B) After peak expression of UNO_N-, UNO_M- and UNO_C-EGFP in early spermatocytes (see panel A), maintenance at low levels in late spermatocytes was detectable in case of UNO_N-EGFP and UNO_C-EGFP, as documented by high resolution of images from testes squash preparations. While at the S5 stage, UNO_N-EGFP and UNO_C-EGFP were in sub-nucleolar foci in spermatocytes heterozygous for the unocc1 null allele (uno-/+) (comparable to full-length UNO-EGFP, see Fig 5F), they displayed an abnormal diffuse nucleolar localization in unocc1 homozygous spermatocytes (uno-/-). At the S6 stage, UNO_N-EGFP and UNO_C-EGFP were in weak dots on the sex chromosome bivalent in uno-/+ spermatocytes and not detectable in uno-/- spermatocytes. Scale bars = 20 (A) and 5 (B) μm. (PDF)