Fig. 1.

knon mutant and knockdown spermatids show aberrant Nebenkern elongation but have an intact membrane potential. Phase-contrast micrographs of live squashed testis preparations showing post-meiotic spermatids from wild-type (a, c, and e) and homozygous knon ^ms(2)1400 males (b, d, f, h) at the early round (onion) stage (a-b), the early elongation stage (c-d), and later in spermatid elongation (e-f). g RNAi knockdown of knon in the testis recapitulates the mutant phenotype, with unelongated Nebenkerne (arrow) in nearly mature elongating spermatid cysts. h Paired phase-contrast and fluorescence micrographs of an elongating spermatid cyst from a knon ^ms(2)1400 /Df(2R)7E male. Rhodamine 123 uptake by the unelongated mitochondrial derivatives (arrow) in a nearly mature spermatid cyst indicates ongoing respiratory activity. Scale bar 20 μm