Conserved and Exapted Functions of Nuclear Receptors in Animal Development

Abstract

The nuclear receptor gene family includes 18 members that are broadly conserved among multiple disparate animal phyla, indicating that they trace their evolutionary origins to the time at which animal life arose. Typical nuclear receptors contain two major domains: a DNA-binding domain and a C-terminal domain that may bind a lipophilic hormone. Many of these nuclear receptors play varied roles in animal development, including coordination of life cycle events and cellular differentiation. The well-studied genetic model systems of Drosophila, C. elegans, and mouse permit an evaluation of the extent to which nuclear receptor function in development is conserved or exapted (repurposed) over animal evolution. While there are some specific examples of conserved functions and pathways, there are many clear examples of exaptation. Overall, the evolutionary theme of exaptation appears to be favored over strict functional conservation. Despite strong conservation of DNA-binding domain sequences and activity, the nuclear receptors prove to be highly-flexible regulators of animal development.

Transcriptomic analysis of female and male gonads in juvenile snakeskin gourami (Trichopodus pectoralis)

“…The photoreceptor-specific nuclear receptor (nr2e3) is an orphan nuclear receptor essential for the development and function of photoreceptor cells 42 . The function of nr2e3 was related to testis development 43 . The expression of spermatogenesis-associated serine-rich protein 1 (spats1) was demonstrated as testis-specific and expressed during spermatogenesis, and a particularly high expression level was observed during meiosis of the first spermatogenic wave, mainly in pachytene spermatocytes 44,45 .…”

Genome streamlining in a minute herbivore that manipulates its host plant

“…However, no homologues of the evolutionary conserved NRs HNF4, HR39, HR78 and HR83 (Bodofsky et al, 2017;Bonneton and Laudet, 2012), nor a homologue of the T. urticae Photoreceptor-specific NR (PNR), were detected in the A. lycopersici genome, even though HR78, HNF4 and PNR are present in D.…”

Functional characterization of ultraspiracle in Leptinotarsa decemlineata using RNA interference assay

“…Given that the expression levels of EcRA, HR3, HR4, E74 and E75 in LdUSP RNAi final instar larvae and the mRNA levels of EcRA, EcRB, HR3, HR4, E74 and E75 in LdUSP-depleted penultimate instar beetles were similar to those in their corresponding controls, our results in this survey suggest that USP plays some roles in larval metamorphosis except as the partner of heterodimeric receptor to activate the downstream 20E signalling genes. In fact, some functions independent of EcR, and therefore independent of E75-HR3 cascade, have been explored in Dipteran USPs in D. melanogaster and the yellow fever mosquito A. aegypti (Oro et al, 1992;Segraves, 1994;Sutherland et al, 1995;Bodofsky et al, 2017). The Dipteran USPs also heterodimerize with other nuclear receptors such as hormone receptors 38 and 78, the Seven-up protein (Sutherland et al, 1995;Hirai et al, 2002;Baker et al, 2003;Zhu et al, 2003) or Met (Li et al, 2007) to implement their functions.…”

“…Second, as a nuclear receptor, USP may heterodimerize with other nuclear receptors except EcR (Buszczak and Segraves, 2000;Hill et al, 2013). In fact, some functions independent of EcR, and therefore independent of E75-HR3 cascade, have been explored in Dipteran USPs in D. melanogaster and the yellow fever mosquito Aedes aegypti (Oro et al, 1992;Segraves, 1994;Sutherland et al, 1995;Bodofsky et al, 2017). The Dipteran USPs also heterodimerize with other nuclear receptors such as hormone receptors 38 and 78, the Seven-up protein (Sutherland et al, 1995;Hirai et al, 2002;Baker et al, 2003;Zhu et al, 2003) or Methoprene-tolerant (Met) (Li et al, 2007).…”