Tunicate pregnane X receptor (PXR) orthologs: Transcript characterization and natural variation

详细信息    查看全文

• 作者：Ingrid Richter^a ; ^b ; ^{Ingrid.Richter@cawthron.org.nz" class="auth_mail" title="E-mail the corresponding author} ; Andrew E. Fidler^a ; ^c ; ^d
• 关键词：AF-1 ; transcription activation function 1 ; AR ; androgen receptor ; BsVDR/PXR伪 ; Botryllus schlosseri VDR/PXR ortholog 伪 ; BSA ; bovine serum albumin ; bp ; base pair ; CAR ; constitutive androstane receptor ; CiVDR/PXR伪 ; Ciona intestinalis VDR/PXR ortholog 伪 ; CiVDR/PXR尾 ; Ciona intestinalis VDR/PXR ortholog 尾 ; DBD ; DNA-binding domain ; dN/dS ; ratio of non-synonymous substitutions per non-synonymous site (dN) to synonymous substitutions per synonymous site (dS) ; ER ; estrogen receptor ; FXR ; farnesoid X recep
• 刊名：Marine Genomics
• 出版年：2015
• 出版时间：October 2015
• 年：2015
• 卷：23
• 期：Complete
• 页码：99-108
• 全文大小：610 K

文摘

Vertebrate pregnane X receptor (PXR, NR1I2), a ligand-activated nuclear receptor (NR), regulates expression of detoxification genes. Vertebrate PXR orthologs may adaptively evolve to bind deleterious/toxic xenobiotics typically encountered by organisms from their diet. Tunicates (phylum Chordata) are marine filter-feeders that form a sister clade to the Vertebrata. Genomes of two tunicate taxa, Ciona intestinalis and Botryllus schlosseri, encode at least two PXR orthologs (abbreviated VDR/PXR伪 and 尾). Here we report characterization of the transcript structures and sequence variation of three tunicate PXR orthologs: C. intestinalis VDR/PXR伪 and 尾, and B. schlosseri VDR/PXR伪. The three predicted proteins consist of both DNA-binding (DBD) and ligand-binding (LBD) domains typical of NRs. The C. intestinalis VDR/PXR尾 LBD may be significantly larger than that of the VDR/PXR伪 orthologs. In both tunicate taxa, the mRNAs were characterized by high frequencies of single nucleotide polymorphisms (SNPs, ca. 3 SNPs/100 base pairs). The majority of SNPs were synonymous and standard tests (Tajima's D, d_N/d_S ratios) indicated strong purifying selection. However, one base pair frameshift allelic variants were found in the C. intestinalis VDR/PXR伪 and 尾 genes. The predicted proteins consisted of a DBD but lacked an LBD. The persistence of these variants may possibly reflect constitutive expression of detoxification genes as a selective advantage in the marine environment. These results provide a foundation for further investigations into the molecular evolution, population genetics and functioning of tunicate receptors involved in detection of marine bioactive compounds.