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Hormonal control and target genes of ftz‐f1 expression in the honeybee Apis mellifera: a positive loop linking juvenile hormone, ftz‐f1, and vitellogenin

Mello, T. R. P., Aleixo, A. C., Pinheiro, D. G., Nunes, F. M. F., Cristino, A. S., Bitondi, M. M. G., Barchuk, A. R., Simões, Z. L. P.
Insect molecular biology 2019 v.28 no.1 pp. 145-159
Apis mellifera, adult development, ecdysterone, enzymes, gene expression, gene expression regulation, genes, honey bees, hormonal regulation, hormone receptors, juvenile hormones, juveniles, prophenoloxidase, queen insects, vitellogenin, worker insects
Ftz‐f1 is an orphan member of the nuclear hormone receptor superfamily. A 20‐hydroxyecdysone pulse allows ftz‐f1 gene expression, which then regulates the activity of downstream genes involved in major developmental progression events. In honeybees, the expression of genes like vitellogenin (vg), prophenoloxidase and juvenile hormone‐esterase during late pharate‐adult development is known to be hormonally controlled in both queens and workers by increasing juvenile hormone (JH) titres in the presence of declining levels of ecdysteroids. Since Ftz‐f1 is known for mediating intracellular JH signalling, we hypothesized that ftz‐f1 could mediate JH action during the pharate‐adult development of honeybees, thus controlling the expression of these genes. Here, we show that ftz‐f1 has caste‐specific transcription profiles during this developmental period, with a peak coinciding with the increase in JH titre, and that its expression is upregulated by JH and downregulated by ecdysteroids. RNAi‐mediated knock down of ftz‐f1 showed that the expression of genes essential for adult development (e.g. vg and cuticular genes) depends on ftz‐f1 expression. Finally, a double‐repressor hypothesis‐inspired vg gene knock‐down experiment suggests the existence of a positive molecular loop between JH, ftz‐f1 and vg.