Sex-specific development in haplodiploid honeybee is controlled by the female-embryo-specific activation of thousands of intronic lncRNAs. Apis mellifera

Sex determination in the honeybee (Apis mellifera) is governed by the queen-controlled unfertilization or fertilization of embryo, though the mechanisms of determination are poorly understood. Here, we obtained the transcriptomes from individual worker and drone embryo during the embryonic development (day 1 to day 3). We show that transcriptional difference between worker and drone embryo is very small during the first day of hatching, during which sex-determinant gene csd expresses similarly. Differential transcription between worker and drone embryo bursts at day 2, among which csd is induced in worker embryo at day 2 and sex-lethal gene sxl is repressed in male embryo. An unexpected global regulation of alternative splicing accompanies the honeybee embryonic development, and male and worker embryo show distinct regulatory patterns and mechanisms. This study suggests the honeybee sex determination is more globally controlled at both the transcriptional and alternative splicing levels. Overall design: We collected 2 groups of worker and male (drone) embryo laid by two different honeybee queens. embryo were collected at 1-day (24 hour), 2-day (48 hour) and 3-day (72 hour) after laying. Three worker and male embryo were collected for each time point. A total of 36 embryo were collected for single-embryo RNA-seq.