TAIMAN, a new modulator of insect circadian clock
Most living creatures need to synchronize their rhythmic biological functions with the 24-hour day/night cycle of Earth. Instead of pocket watches or cell phones, they use intracellular molecular clocks to anticipate the daily recurring changes and adjust their activity, metabolism, and biochemical processes to a 24-hour day/night regime. Those circadian clocks are at the genetic level remarkably conserved among mammals and insects. Thanks to the unparalleled genetic tools of the fruit fly Drosophila melanogaster, all key components of the clock seemed to be identified, most of them during a two-decade period from ~1990-2010. Our recent study in PLOS Genetics shows, for the first time in insects, that the protein TAIMAN is a new modulator of the circadian clock. The removal of TAIMAN from the adult linden bug Pyrrhocoris apterus or the German cockroach Blattella germanica males slows the clock down by 2–4 hours. Circadian clocks often adjust animals’ physiology through various hormones and neuropeptides. Insect endocrinology is dominated by the steroid hormone ecdysone and terpenoid hormone juvenile hormone. TAIMAN is closely engaged in both juvenile hormone and ecdysone receptor signaling. However, the circadian role of TAIMAN presented here modulates the clock in a hormone-independent way. Importantly, TAIMAN is related to the mammalian SRC-2 protein, which is involved in regulating circadian clock machinery in mice (Mus musculus). Thus, the novel role we describe for TAIMAN in insects may have a counterpart in mammalian physiology.
Graphical summary of TAIMAN (TAI) /Steroid Receptor Coactivator 2 role in circadian clock. tai/SRC ancestor gene got triplicated in a jawed vertebrate lineage, whereas insects possess a single tai gene. Although Pyrrhocoris apterus and Blattella germanica lineages separated ~380 million years ago, tai silencing in both species slowed the pace of the circadian clock. Homozygous Steroid Receptor Coactivator-2 (SRC-2) knockout (SRC-2-/-) mice (Mus musculus) exhibit a range of aberrant behavioral activities during light/dark cycles, from bimodal/phase-advanced wheel-running locomotor activity to complete arrhythmicity.
Vlastimil Smykal, Lenka Chodakova, Marketa Hejnikova, Kristina Briedikova, Bulah Chia-Hsiang Wu, Hana Vaneckova, Ping Chen, Anna Janovska, Pavlina Kyjakova, Martin Vacha, David Dolezel (2023): Steroid receptor coactivator TAIMAN is a new modulator of insect circadian clock. PLOS GENENTICS https://doi.org/10.1371/journal.pgen.1010924