Single-cell Transcriptomic Analysis of Honeybee Brains Identifies Vitellogenin As Caste Differentiation-Related Factor

The honeybee (Apis mellifera) is a well-known eusocial insect. In honeybee col-onies, thousands of sterile workers, including nurse and forager bees, perform various tasks within or outside the hive, respectively. The queen is the only fertile female and is responsible for reproduction. The queen and workers share similar genomes but occupy different caste statuses. We established single-cell tran-scriptomic atlases of brains from queens and worker subcastes and identified five major cell groups: Kenyon, optic lobe, olfactory projection, glial, and hemo-cyte cells. By dividing Kenyon and glial cells into multiple subtypes based on cred-ible markers, we observed that vitellogenin (vg) was highly expressed in specific glial-cell subtypes in brains of queens. Knockdown of vg at the early larval stage significantly suppressed the development into adult queens. We demonstrate vg expression as a "molecular signature" for the queen caste and suggest involve-ment of vg in regulating caste differentiation.