6 – Evolution of Nuclear Receptors in Insects

Publisher Summary This chapter discusses the evolution of nuclear receptors in insects. Nuclear receptors are metazoan transcription factors activated by small lipophilic ligands, such as steroid hormones, thyroid hormones, retinoids, vitamin D, or fatty acids. The availability of the ligand controls the transcriptional activity of nuclear receptors. Nuclear receptors are involved in a considerable diversity of developmental and physiological processes. Nuclear receptors are present in all metazoans, and only in metazoans. They are absent from the genome of the unicellular Monosiga brevicollis, which belongs to choanoflagellates, the sister group of animals. The set of nuclear receptors is strongly conserved in pterygote insects, ranging from 19 to 21 genes that are distributed into 22 groups. Unlike nematodes and chordates, insects did not experience any lineage-specific expansions within the nuclear receptors family.