Molecular Characterization and Expression Profiling of Nuclear Receptor Gene Families in Oriental Fruit Fly, Bactrocera Dorsalis (Hendel)

Abstract

The oriental fruit fly (Bactrocera dorsalis) is a pest that causes large economic losses in the fruit and vegetable industry, so its control is a major challenge. Nuclear receptors (NRs) are a superfamily of ligand-dependent transcription factors that directly combine with DNA to regulate the expression of downstream target genes. NRs are closely associated with multiple physiological processes such as metabolism, reproduction, and development. Through sequence searches and analysis, we identified 21 B. dorsalis NR genes, all of which contained at least one of the two characteristic binding domains. On the basis of the conserved sequences and phylogenetic relationships, we divided the 21 NR genes into seven subfamilies. All members of the NR0 subfamily and BdHR83, which belonged to the NR2E group, lacked ligand-binding domains. The BdDSF and BdHR51, which also belonged to the NR2Egroup, and BdE78 (which belonged to the NR1E group) all lacked DNA-binding domains. The BdDSF and BdHR83 sequences were incomplete, and were not successfully amplified. Development-and tissue-specific expression profiling demonstrated that the transcript levels of the 19 NR genes varied considerably among eggs, larva, pupae, and adults, as well as among larval and adult male and female tissues. Our results will contribute to a better understanding of NR evolution and expand our knowledge of B. dorsalis physiology.Insects 2020, 11, 126 2 of 15 in recognizing hormone response elements. The D domain functions as a hinge between the DBD and the ligand-binding domain (LBD). The LBD (also known as E domain) contains a hydrophobic ligand-binding pocket that is specific to each receptor and is the source of the sequence variability within the LBD. In addition, the LBD domain mediates dimerization and the ligand-dependent transcriptional activation function (AF-2) [4]. The C-terminal contains the F domain, which is not present in all NRs and is highly diverse.A large number of NR gene sets have been characterized from the whole-genome sequence of many animals. For example, 48 NRs were identified in the human genome [5], over 270 NRs have been found in Caenorhabditis elegans [6], and 49 and 47 were found in mouse and rat, respectively [7]. Surprisingly, only 21 NRs were found in Drosophila melanogaster [8], 19 in Bombyx mori [9], 22 in Apis mellifera [10], and 21 in Tribolium castaneum [11].In D. melanogaster, seven NR genes that are regulated directly by 20E have been identified, namely EcR, E75, E78, FTZ-F1, HR3, HR4, and HR39 [12]. Among them, E75 is the primary response gene of 20E. The others are secondary response genes that are maximally expressed after 20E-induced protein synthesis has begun [13]. The ligand-receptor complex of 20E-EcR-USP induces the expression of the 20E primary response gene. Then, the cascade of 20E secondary response genes, which is induced by the transcription factor encoded by the 20E primary response gene, amplifies the 20E signal by regulating the expression of the secondary response genes (e.g., HR3, HR4, and FTZ...

Role of Endocrine System in the Regulation of Female Insect Reproduction

“…E75 is a primary response gene, while HR3 is a secondary response gene [22]. Twenty-one nuclear receptors (NRs) were identified from the Bacterocera dorsalis [23], while Halloween genes encode for the enzymes (like cytochrome P450) necessary for catalyzing the last step of the ecdysteroid biosynthesis. In Schistocerca gregaria, shade (a Halloween gene) was found to encode 20-hydroxylase, which in turn catalyzed the conversion of 20E from ecdysone (E) [24].…”

Recent development in ecdysone receptor of crustaceans: current knowledge and future applications in crustacean aquaculture

“…LBD is a multifunctional domain that plays several roles in NR, such as to (i) mediate receptor homodimerisation or heterodimerisation, (ii) activate ligand‐binding pocket that binds lipophilic ligands, (iii) interact with other proteins as co‐activators or co‐repressors in transcriptional activity, and (iv) mediate transactivation function by ligand‐dependent activation function 2 (AF‐2; Billas & Moras 2005; Germain et al 2006; Nakagawa & Henrich 2009; Jin & Li 2010). The F domain positioned at the C‐terminal of NR is neither conserved in sequence nor found in all NRs (Yang et al 2020).…”

Genome-Wide Characterization of the Nuclear Receptor Gene Family in Macrostomum lignano Imply Its Evolutionary Diversification

“…Recently, the rapid developments in the genome sequencing have facilitated a genome-wide identification of NR family members in many species. The NR gene repertoires have been characterized in different lineages with a clear species-dependent pattern from invertebrates to vertebrates, such as 2 members in sponge, 4 in placozoan, ≥250 in nematodes, ∼21 in arthropods, ∼48 in mammals, and 66-137 in teleost (Bertrand et al, 2004;Bridgham et al, 2010;Cheng et al, 2015;Yang et al, 2020). These data suggest the evolutionary complexity of the NR family, which is likely driven by gene duplication and loss (Fonseca et al, 2020).…”