Fig. 1: Identification of a male-specific dsx^M2 transcript through intron retention.

a Schematic structure of the dsx gene. Boxes: exons; white and gray boxes: common 5’-UTR and coding sequences respectively in both sexes; red and pink: coding and 3’-UTR sequences of the female-specific exon; dark and light blue: coding and 3’-UTR sequences of male-specific exons. Primers against sex-specific sequences are indicated. b, c Relative mRNA expression levels of presumed dsx^Mcycle at 60% humiditytranscript (b, primer 1) and dsx^F transcript (c, primer 2) in wtcs and dsx mutant (dsx^683-7058/dsx^1649-9625) males and females. n = 9 based on three replicates for each. ***p < 0.001, Mann–Whitney U test. Note that a dsx transcript (arrowhead) is detected in males using the primer against the female-specific transcript (b). d, e Reverse transcription PCR (RT-PCR), using three pairs of primers as indicated (d), and sequencing identify the male-specific dsx^M2 transcript, in addition to the female-specific dsx^F transcript, in both wtcs and w¹¹¹⁸ flies (e). For primer 1: 462bp and 348bp for male and female products, respectively; for primer 2: 1833bp and 1719bp for male and female products, respectively; for primer 3: 1069bp and 955bp for male and female products, respectively. f Illustration of the male-specific dsx^M2 transcript, in addition to previously identified dsx^M and dsx^F transcripts. g The dsx^M2 transcript differs from the dsx^F transcript with the 114 bp intron (in green) retained. Red letters (tga) indicate the stop codon inside the retained intron.