Gene targets and developmental regulation of the honeybee Apis mellifera ftz-f1

Ftz-f1 (Fushi tarazu transcription factor 1) is an orphan member of the nuclear hormone receptor superfamily, with one of its transcriptional variant (βFtz-f) being homolog of the vertebrate SF1. Ftz-f1 gene is induced after a 20E pulse, and allows for the expression of down-stream genes in processes leading to major switching in development, like those of metamorphosis. In honeybees, the expression of some genes (e.g. vitellogenin, vg; pro-phenoloxidase, pro-Po; juvenile hormone esterase, jhe) during the last part of pharate-adult development is known to be under hormonal control [increasing juvenile hormone titers (JH) in the presence of declining levels of ecdysteroids], both, in queens and workers. However, despite the USP involvement in the gene expression cascade promoted by JH, it does not seem to be the unique mediator of its activity, and, thus, we are still ignorant of the molecular factors regulating the expression of these genes, at least, during the critical period of pharate-adult development. Here, we show that Amftz-f1 has caste-specific transcription profile in fat bodies during this developmental stage, peaking just at the moment of the resuming of JH titers increase in the presence of low levels of ecdysteroids. Knock-down experiments (by RNAi) showed that the expression of genes essential to adult development (e.g. vg, and cuticular protein genes) depends on ftz-f1. Our results suggest that Amftz-f1 can also be considered a competence factor to the expression of several genes during pharate-adult development, and, thus, as a key actor in one of the last developmental processes leading to caste differentiation in A. mellifera. RNA samples (from pools of 3-5 whole body workers) from knocked-down and control pharate-adults were hybridized in pairs (dsftz-f1/dsGFP) and in dye-swaps (Cy3/Cy5), twice, then, combined in silico.